Windows 10 Home PC 32 GB RAM but only 16 GB available to Windows (Dell Precision T7400, upgraded from Win 7 Home)

My wife's Dell Precision T7400 PC has 32 GB RAM (I upgraded it recently from
4x2GB DIMMs to 4x8GB DIMMs). It originally had Windows 7 Home installed, and
I know that this has a 16 GB limit, so I wasn't too surprised to see in
Control Panel | System that it reported "32 GB RAM (16 GB available)".

Having just upgraded it to Windows 10 Home 1803 which has a much higher max
memory, I'm puzzled that Settings | System (and Control Panel | System)
still reports "32 GB, 16 GB available".

I've check MS Config | Boot | Advanced and the "Maximum Memory" box is not
ticked to enforce a lower limit.

What am I doing wrong? The PC clearly sees that it has 32 GB, right from the
BIOS config menu up to Control Panel | System. How do I enable Windows to
use the additional 16 GB of RAM?

NY wrote:
My wife's Dell Precision T7400 PC has 32 GB RAM (I upgraded it recently
from 4x2GB DIMMs to 4x8GB DIMMs). It originally had Windows 7 Home
installed, and I know that this has a 16 GB limit, so I wasn't too
surprised to see in Control Panel | System that it reported "32 GB RAM
(16 GB available)".

Having just upgraded it to Windows 10 Home 1803 which has a much higher
max memory, I'm puzzled that Settings | System (and Control Panel |
System) still reports "32 GB, 16 GB available".

I've check MS Config | Boot | Advanced and the "Maximum Memory" box is
not ticked to enforce a lower limit.

What am I doing wrong? The PC clearly sees that it has 32 GB, right from
the BIOS config menu up to Control Panel | System. How do I enable
Windows to use the additional 16 GB of RAM?

The BCD can limit memory.

https://docs.microsoft.com/en-us/win...ipulate-memory

In an administrator command prompt window, type this and check:

bcdedit

Usually, something like this isn't needed. This dumps "noise"
in the file.

bcdedit /enum

I would have thought MSConfig would be doing the same thing.
But maybe it's intended for boot.ini instead ?

The memory license for Win10 Home is 128GB, Win10 Pro is 2TB
(enough for an Epyc). You're right, that this should not be
happening - but what could be happening is the BCD values
were preserved on the upgrade install.

https://docs.microsoft.com/en-us/win...ndows-releases

Paul

Paul wrote:
NY wrote:
My wife's Dell Precision T7400 PC has 32 GB RAM (I upgraded it
recently from 4x2GB DIMMs to 4x8GB DIMMs). It originally had Windows 7
Home installed, and I know that this has a 16 GB limit, so I wasn't
too surprised to see in Control Panel | System that it reported "32 GB
RAM (16 GB available)".

Having just upgraded it to Windows 10 Home 1803 which has a much
higher max memory, I'm puzzled that Settings | System (and Control
Panel | System) still reports "32 GB, 16 GB available".

I've check MS Config | Boot | Advanced and the "Maximum Memory" box is
not ticked to enforce a lower limit.

What am I doing wrong? The PC clearly sees that it has 32 GB, right
from the BIOS config menu up to Control Panel | System. How do I
enable Windows to use the additional 16 GB of RAM?

The BCD can limit memory.

https://docs.microsoft.com/en-us/win...ipulate-memory


In an administrator command prompt window, type this and check:

** bcdedit

Usually, something like this isn't needed. This dumps "noise"
in the file.

** bcdedit /enum

I would have thought MSConfig would be doing the same thing.
But maybe it's intended for boot.ini instead ?

The memory license for Win10 Home is 128GB, Win10 Pro is 2TB
(enough for an Epyc). You're right, that this should not be
happening - but what could be happening is the BCD values
were preserved on the upgrade install.

https://docs.microsoft.com/en-us/win...ndows-releases


** Paul

I upgraded from Win 7 Pro to Win 10 Pro without that problem.

On 11/12/2018 8:09 AM, Weatherman wrote:
I upgraded from Win 7 Pro to Win 10 Pro without that problem.

Both Win 7 Pro and Win 10 Pro have much higher limits than the Home
versions of those OS. In Win 7 Home Basic, the limit was 8 GB, that was
increased to 16 GB for Home Premium, and 192 GB for everything above that.

Win 8/8.1 basic had a limit of 128 GB, and 512 GB for everything above that.

Win 10 Home also has a limit of 128 GB, like Win 8 basic, while the
upper limit has been extended to 2 TB for everything above that.

Yousuf Khan

"Paul" wrote in message
news
NY wrote:
My wife's Dell Precision T7400 PC has 32 GB RAM (I upgraded it recently
from 4x2GB DIMMs to 4x8GB DIMMs). It originally had Windows 7 Home
installed, and I know that this has a 16 GB limit, so I wasn't too
surprised to see in Control Panel | System that it reported "32 GB RAM
(16 GB available)".

Having just upgraded it to Windows 10 Home 1803 which has a much higher
max memory, I'm puzzled that Settings | System (and Control Panel |
System) still reports "32 GB, 16 GB available".

I've check MS Config | Boot | Advanced and the "Maximum Memory" box is
not ticked to enforce a lower limit.

What am I doing wrong? The PC clearly sees that it has 32 GB, right from
the BIOS config menu up to Control Panel | System. How do I enable
Windows to use the additional 16 GB of RAM?

The BCD can limit memory.

https://docs.microsoft.com/en-us/win...ipulate-memory

In an administrator command prompt window, type this and check:

bcdedit

Usually, something like this isn't needed. This dumps "noise"
in the file.

bcdedit /enum

I would have thought MSConfig would be doing the same thing.
But maybe it's intended for boot.ini instead ?

The memory license for Win10 Home is 128GB, Win10 Pro is 2TB
(enough for an Epyc). You're right, that this should not be
happening - but what could be happening is the BCD values
were preserved on the upgrade install.

https://docs.microsoft.com/en-us/win...ndows-releases


Thanks for this. I forgot to say (but it's probably obvious) that it's 64
bit, not 32 bit.

I've run bcdedit but I'm not sure how to interpret the results:


Windows Boot Manager
--------------------
identifier {bootmgr}
device partition=C:
description Windows Boot Manager
locale en-US
inherit {globalsettings}
default {current}
resumeobject {5c85c246-e694-11e8-ba35-a13e094ed3ed}
displayorder {current}
toolsdisplayorder {memdiag}
timeout 30

Windows Boot Loader
-------------------
identifier {current}
device partition=C:
path \WINDOWS\system32\winload.exe
description Windows 10
locale en-US
inherit {bootloadersettings}
recoverysequence {dfb44823-e651-11e8-81a7-be8dede06390}
displaymessageoverride Recovery
recoveryenabled Yes
allowedinmemorysettings 0x15000075
osdevice partition=C:
systemroot \WINDOWS
resumeobject {5c85c246-e694-11e8-ba35-a13e094ed3ed}
nx OptIn
bootmenupolicy Standard

both "bcdedit" and "bcdedit /enum" give identical output.


I've seen elsewhere that CPU-Z should be run to list the memory. V1.86.0.x64
reports:

CPU: Intel Xeon E5420

Mainboard: Dell 0RW199
Chipset Intel 5400B
Southbridge 6321ESB
BIOS: Dell A01 1/31/08

Memory:
32 GB FB-DDR2
DRAM Freq 332.5 MHz
FSBRAM 1:1
CAS lat 5
RAS.CAS 5
RAS precharge 5
Cycle RAS 15
Bank cycle 20

SPD:
Slots 1-8 blank
Slots 9-12 FB-DDR2, PC2-5300 (333 MHz), Samsung
four different serial numbers, two different dates (2 are 08/09 and
2 are 26/09)

The memory was ordered as a 32 GB kit "for Dell T7400" (as described by the
vendor).


The PC has loads of slots, some on risers, but I installed the memory
according to Dell's instructions, doing a like-for-like replacement of the
original 4x 2 MB DIMMs that were supplied with the 4x 8 MB DIMMs that I
bought.


Any further suggestions?

In case it's relevant, the Control Panel | System screen shows that Windows
is activated, so it's not an unregistered version of Win 10 - it's inherited
the licensing of Win 7 Home Premium during the upgrade.

NY wrote:

Memory:
32 GB FB-DDR2

SPD:
Slots 1-8 blank
Slots 9-12 FB-DDR2, PC2-5300 (333 MHz), Samsung

The memory was ordered as a 32 GB kit "for Dell T7400" (as described by the
vendor).

The PC has loads of slots, some on risers, but I installed the memory
according to Dell's instructions, doing a like-for-like replacement of the
original 4x 2 MB DIMMs that were supplied with the 4x 8 MB DIMMs that I
bought. | |
| |
GB, not MB -----'-----------------------------------------'

Why are any of the memory modules on risers?

There are 8 memory slots. You only have 4 memory modules. Why were
they plugged into the 2nd bank instead of the first?

https://downloads.dell.com/manuals/a...uide_en-us.pdf

From the online manual, the risers are only needed if you want to use 16
memory modules (above the 8 provided as memory slots on the mobo).

The manual also states the modules sizes allowed in the slots are 512MB,
1GB, 2GB, and 4GB. 8GB is not mentioned. If the slots don't have
sufficient address lines to access the higher memory capacity then you
can't use the higher capacity memory modules.

You get the 32GB maximum memory capacity (without risers) by using 8x4GB
memory modules, not by putting in 4x8GB modules. You can get up to 64GB
memory by using the risers (16x4GB) but you are still limited to 4GB
modules.

According to the manual, the memory risers are numbered, and its number
must match the memory slot number. Only 4 risers can be used and only
in the white memory slots. If risers are used, slots 5-8 on the mobo
must be left vacant. Each riser can hold 4 memory modules, so a total
of 16 memory modules (4x4) if the risers are used for a total of 64 GB
of memory using the 4 GB maximum size for each memory module.

Also, on a riser card, you cannot populate a slot before the same slot
has been populated on another riser. That is, you must populate DIMM1
on riser1 and not populate any of its other slots until you have
populated DIMM1 in the other risers. So, by using the risers, your 4
memory modules would all have to be in the DIMM1 slot of 4 risers. When
a slot on a riser is populated, the same slot on the other risers must
also be populated; i.e., you must install in sets of 4 to populate the
same DIMM1 slot in each of the 4 risers. However, the specs still say
the maximum module size is 4 GB, not 8 GB.

To achieve a 32 GB capacity in memory, seems you could've used 8x4GB
memory modules just in the 8 memory slots on the mobo, or 8x4GB in the
risers with DIMM1 and DIMM2 populated in each of the 4 risers that must
be used as a set.

There 8 memory slots on the mobo. With the 4 GB max size per memory
module, that gives you 32 GB of total memory. You don't get to put in 8
8 GB modules for 64 GB with the onboard slots. Similarly, with the
risers, you get to use 16x4 GB memory modules for 64 GB total memory,
not with 16x8 GB memory modules (for 128 GB total). Whether you use
the onboard slots or the risers in them, you are still limited to 4 GB
memory modules.

Just WHO is/was the "vendor" where you bought this 32GB kit that stated
it was for your computer model? Did the vendor specifically state that
their "kit" was for your model? They should've sold you eight 4GB
modules, not four 8GB modules. Or did you assume you could double the
memory module size and buy a 4-count package of DIMMs (i.e., the vendor
never stated their package was for your specific model)?

I'm going by the Dell manual that I found for a T7400 model. Maybe
there are different model versions that have different memory capacity
and support larger memory modules. The manual that I found (Dell sucks
for finding support on long discontinued models - I had to use a search
engine outside of dell.com to find the manual at dell.com) says 4 GB is
the max size for memory modules and that's whether you use the onboard
slots or the risers to effectively double the slots (not double the
memory module size).

When I went to amazon.com and searched on "dell precision T7400 memory",
all the vendors there were selling memory kits that used 4 GB memory
modules, or smaller. None were selling kits with DIMMs over 4 GB. I
did find Dell's spec sheet on the T7400 at:

https://www.dell.com/downloads/globa..._specsheet.pdf

That says max memory (with the risers) is 128 GB, not the 64 GB max
noted in the manual. Could be Dell came out with a later version of the
same model that added another address line to double the maximum memory
capacity. Even if memory modules are not yet available at a higher
capacity when the manual is published, the manual shouldn't be saying
the max memory module size is 4 GB if the hardware supports 8 GB
modules. Reviews or 3rd party specs published at the time the T7400 was
first released note a 64 GB max memory capacity, not 128 GB.

The SPD info that CPU-z and other similar tools will read from the
memory modules does not reflect what the hardware can support.

"VanguardLH" wrote in message
...
Why are any of the memory modules on risers?

There are 8 memory slots. You only have 4 memory modules. Why were
they plugged into the 2nd bank instead of the first?

I'm not sure. The 4 GB (not 8 GB - I was wrong) that it came with was fitted
by Dell as 4x 1 GB DIMMs on two riser cards. Maybe because it's easier to
remove those risers and fit DIMMs to them than it is to fit the DIMMs
directly to the motherboard when the sockets are at the bottom of a deep
"well" bounded by the walls of the cage that supports risers (if any) and
the walls of the case.

Anyway, I bought the new DIMMs (and the vendor offered 8 GB DIMMs as the
largest size; I hadn't noticed the max 4 GB DIMM in the Dell manual) and
fitted them exactly like-for-like in the risers. At the time I chose to
remove the 4 GB of 1 GB DIMMs, but I've since fitted them in addition.


Anyway, I've solved the problem of Windows reporting (on Control Panel |
System) "Memory 32 GB (16 GB usable)". It's all down to turning on
virtualization in the BIOS!

I started to suspect something when I temporarily replaced the 32 GB with 4
GB as Yousuf suggested, prior to booting like that, shutting down and then
replacing the 32 and letting Windows discover it. With 4 GB, Control Panel |
System reported "4 GB (2 GB usable)". So I was now well below any limit of
16 GB that might have been inherited from Windows 7 64 Home Premium... and
yet it was still reporting that only half the memory was usable. As an
aside, Windows 10 with 4 GB of RAM moves like a wounded snail - it is
painfully SLOW :-)

My wife did some Googling (it's OK as long as you do it in private!) and
discovered many forum postings about Windows 10 reporting "n GB (n/2 GB
usable)" for any value of n.

The two things that were suggested we

- make various BIOS changes, amongst which was to turn on Virtualization
(the rest didn't apply to my BIOS)

- change the page file strategy from "Allow Windows to manage swap file for
all drives" and "System managed sized" to turn off "Allow..." and set
hard-coded minimum of n*1.5 and maximum of n*4, when n is the amount of RAM

The second (which I tried even while I had 4 GB RAM) made no difference to
Control Panel | System and Task Manager | Memory, but turning on
Virtualization is the single thing which instantly made all 4 GB usable.

After that success I decided to be bold and I added the new 8 GB DIMMs as
well (putting the 8s in Slot 1 on each of the four riser banks and the 1s in
Slot 2), to give a total of 36 GB. What would PCs of the 1990s have made of
36 GB RAM, at a time when a few MB was luxury and with DOS you had to juggle
with HIMEM and Upper Memory (been there, done that - trying to work out the
order to load different network stacks to make best use of memory under 1
MB).

And the PC came up and reported 36 MB (and all of it usable/available to
Windows).

I'm not sure what the best advice is on page file strategy - hard-coded
versus letting Windows manage it. Any comments, anyone? Should I reset it
back to the default of "Allow..." and System Managed size?



To sum up: the "16 GB available" was not a carry-over from Windows 7 that
had been on the PC before. It was an inherent restriction that seems to
affect Windows 10 (at least on this PC), that half the memory (no matter how
much you have) seems to be "hidden" from Windows unless virtualization is
turned on in the BIOS.

My wife is over the moon to have 36 GB. Not because she needs it but because
she had bought it at great expense (the vendor charged almost the same for
2, 4 or 8 GB DIMMs so she got the biggest) and wanted to be able to make
full use of them if she ever needed to run a memory-hungry app.

NY wrote:


My wife is over the moon to have 36 GB. Not because she needs it but
because she had bought it at great expense (the vendor charged almost
the same for 2, 4 or 8 GB DIMMs so she got the biggest) and wanted to be
able to make full use of them if she ever needed to run a memory-hungry
app.

You should be testing with memtest, and do at least
one full pass. (There's a pass counter on the 640x480 screen.)

http://memtest.org/

Downloads are half way down the web page.

Various media formats are available, to suit
machines with fewer storage options.

I recommend memory testing, on average, about once
a year, as part of preventive maintenance.

That's not the only test you can run, but it does
do a stuck-at test for you. Memory failures come in
a couple types. Stuck-at faults are memory bits
that can no longer be flipped. Transient faults
(never the same address, twice) can be cause by
bus noise issues. The FBDIMM isn't likely to have
bus noise issues, but you can still have stuck bits
on the memory chips themselves.

Memtest also has a bandwidth display, which you can
check to see if the value makes sense or not. For
example, my quad channel system here, the measured
bandwidth is only 25% of theoretical, which means
the thing basically runs dual channel mode inside.
Not a big deal, except in bar bets.

Paul

NY wrote:

I'm not sure what the best advice is on page file strategy - hard-coded
versus letting Windows manage it. Any comments, anyone? Should I reset it
back to the default of "Allow..." and System Managed size?

In the past, I set max and min pagefile size to the same 1.5*N value
(where N is my physical system RAM). Having the same size for min and
max meant the pagefile stayed the same size hence preventing further
fragmentation of that file (after doing a defrag of it). Later with an
8GB system, it seemed ridiculous to have 12GB of fixed space allocated
to a pagefile when there was 8GB of real RAM available. I knew that a
zero-sized pagefile was incorrect because Windows wants some, some
programs will error or fail if they request some but none is available,
and some games error, fail to load, or crash without some (they want to
offload their textures and objects into the pagefile which is on the
disk because access is faster than doing file I/O on the disk). So I
reduced the pagefile down to 4GB which seemed more than large enough.
After a couple years and some updates to Windows and the programs, I
started getting 7A BSODs at infrequent intervals. I did chkdsk /r,
memtest, and a slew of other testing but nothing pointed at defective
hardware and all testing was okay. I noticed the BSODs were after using
Macrium Reflect free to perform a scheduled backup. The backup job
completed okay and even the following verification of the backup. It
was 5 minutes after the backup completed that a BSOD happened.

I had also split the pagefile across 2 drives. If Windows sees part of
the pagefile on a drive other than the one for the OS, it's supposed to
get preference to using that other pagefile space. Now all the pagefile
space is on the SSD. No splitting across drives and different types of
drives (SSD for OS drive, HDD for data drive). I changed to system
managed instead of trying to prevent fragmentation of the file with
varying size (which different min-max values might do and system-managed
would do) because fragmentation on an SSD doesn't cause the slowdown as
it does for seeks on an HDD (the SSD still needs to get optimized
occasionally to reduce fragments to reduce the meta data from all of
them which could exceed the handling supported in the file table and why
in Task Scheduler you'll find a scheduled defrag using MS's tool - so I
reenabled that scheduled event). Although it says 12GB is reserved,
that doesn't mean used. Windows, when pagefile is system managed, will
vary the size of the pagefile as needed. When min is less than max,
them is physically allocated on the drive but the remainder up to the
max is only reserved for if and when it is needed.

I had replaced an HDD with an SSD (and moved the old HDD to a data-only
drive but with some pagefile space). To troubleshoot the BSODs, I moved
all of the pagefile space to the SSD (the OS drive). With the changes
in the pagefile (not split across different types of drives, well, not
split at all and only on the OS drive, and using system managed sizing),
I'll have to wait a month, or two, to see if the BSODs still occur 5
minutes after the backup & verify completes (which go to a different HDD
but that's been chkdsk /r'd and tested, too).

While my SSD is a lot smaller than my HDDs (256GB versus 1TB and 2TB), I
was trying to save space by moving most of the pagefile off the SSD.
That would also reduce the number of writes to the SSD since there is a
max number of writes the SSD can handle. I'd rather have a stable PC
than worry about more writes reducing the lifespan of the SSD. I have
scheduled backups (daily-differential and weekly-full to the internal
HDD, copied to a USB-attached HDD, and monthly-full to USB flash drives)
to recover from hardware failure. I had originally split the pagefile
because file I/O to the pagefile was parallel to writes to the OS drive,
so paging would be faster. That wasn't true anymore when using the SSD
where the other-drive pagefile would now be a lot slow than the part of
the pagefile on the SSD. I had fixed the pagefile size to eliminate its
fragmentation but that's not an issue when using an SSD.

To sum up: the "16 GB available" was not a carry-over from Windows 7 that
had been on the PC before. It was an inherent restriction that seems to
affect Windows 10 (at least on this PC), that half the memory (no matter how
much you have) seems to be "hidden" from Windows unless virtualization is
turned on in the BIOS.

My wife is over the moon to have 36 GB. Not because she needs it but because
she had bought it at great expense (the vendor charged almost the same for
2, 4 or 8 GB DIMMs so she got the biggest) and wanted to be able to make
full use of them if she ever needed to run a memory-hungry app.

Most of the articles that I found on "hardware reserved" for memory
pointed back to the BIOS. A new BIOS version was needed (so it matched
the better capable hardware), devices had been allocated space (e.g.,
onboard video), and other settings that would reserve some memory making
it unavailable to any OS. I had not thought that lack of virtualization
support would cause allocation of memory the OS could not reach.
Because BIOS had been mentioned often, in another reply I had suggested
resetting the BIOS to either its default or optimized config. In my
mind, the Xeon was an old processor, so I didn't think it supported VT-x
virtualization. I haven't dealt with Xeon PCs for a very long time.
https://en.wikipedia.org/wiki/List_o...icroprocessors shows
the CoffeeLake family was released this year.

https://www.intel.com/content/www/us...rocessors.html

I looked up one of the Xeons (probably not yours) and it does list VT-x
as supported. Since VT-x virtualization is supported by the Xeon
processor, seems peculiar that it was disabled in the BIOS. You might
want to reset the BIOS settings. After a reset, check the VT-x option
is enabled (along with other BIOS settings, like AGP aperture size).

You might also consider replacing the CMOS battery. Rarely are the BIOS
settings read directly from the EEPROM chips where the BIOS settings are
stored. Instead during boot the settings are read from the CMOS table
where a copy of the BIOS settings are stored. If the battery goes weak
or dead, the CMOS table can get corrupted. If the CMOS battery is over
5 years old, replace it.

I noticed Device Manager (devmgmt.msc) can let you see what memory
ranges have been reserved for hardware (in the BIOS). Load devmgmt.msc
and go to the View - Resources by connection menu and expand the Memory
node in the tree list. I haven't bothered to figure out which reserved
memory ranges are included in the hardware reserved range. Maybe they
all are. Some info he

https://blogs.technet.microsoft.com/...ysical-memory/

NY wrote:

I hadn't noticed the max 4 GB DIMM in the Dell manual

Though it's not unusual for limits that apply when a product is new (and
are noted in the manual) to be altered over the years by firmware upgrades.

"Paul" wrote in message
news
The BCD can limit memory.

https://docs.microsoft.com/en-us/win...ipulate-memory

In an administrator command prompt window, type this and check:

bcdedit

Usually, something like this isn't needed. This dumps "noise"
in the file.

bcdedit /enum

I would have thought MSConfig would be doing the same thing.
But maybe it's intended for boot.ini instead ?

The memory license for Win10 Home is 128GB, Win10 Pro is 2TB
(enough for an Epyc). You're right, that this should not be
happening - but what could be happening is the BCD values
were preserved on the upgrade install.

https://docs.microsoft.com/en-us/win...ndows-releases

Also, Task Manager shows 16 GB of memory as "hardware reserved":

https://i.postimg.cc/7LPp71Yg/Untitled-1.png

NY wrote:
"Paul" wrote in message
news
The BCD can limit memory.

https://docs.microsoft.com/en-us/win...ipulate-memory


In an administrator command prompt window, type this and check:

bcdedit

Usually, something like this isn't needed. This dumps "noise"
in the file.

bcdedit /enum

I would have thought MSConfig would be doing the same thing.
But maybe it's intended for boot.ini instead ?

The memory license for Win10 Home is 128GB, Win10 Pro is 2TB
(enough for an Epyc). You're right, that this should not be
happening - but what could be happening is the BCD values
were preserved on the upgrade install.

https://docs.microsoft.com/en-us/win...ndows-releases


Also, Task Manager shows 16 GB of memory as "hardware reserved":

https://i.postimg.cc/7LPp71Yg/Untitled-1.png

OK, now we're getting somewhere.

FBDIMMs don't work, if there isn't continuity in the channel.
Seaburg talks to first DIMM. First DIMM talks to second DIMM
in channel. If first DIMM in channel is missing, second DIMM
"floats" and the OS accounting system calls it "hardware reserved".

https://www.hardwaresecrets.com/how-...memories-work/

https://www.anandtech.com/show/2059/4

Check out page 179.

https://downloads.dell.com/manuals/a...uide_en-us.pdf

"You must remove the memory riser cards from the computer in order to
install memory on them. The memory slots on each riser card are numbered
DIMM_1-DIMM_4. Memory must be installed on these cards in the order
that they are numbered; that is, DIMM_1 on riser card 1 must be populated
before DIMM_1 is populated on any other card. DIMM_1 must be populated
on each card before DIMM_2 can be populated on riser card 1, and so on.
Memory must be installed in sets of four with one of the four on each riser
card."

The memory controller ("Seaburg") has four channels.

https://ark.intel.com/products/34474...ory-Controller

There might be eight FBDIMM slots on the motherboard itself. This is
my numbering scheme, *not* the labels on the motherboard (which might
be different). My numbers here are purely to count slots. The
dashed lines indicate serial point-to-point buses.

5--1-- |Seaburg
6--2-- |Northbridge
7--3-- |Quad
8--4-- |channel

If I filled the slots like this:

x 1-- |Seaburg 16GB, 1/2 bandwidth
x 2-- |Northbridge
7 x |Quad #7 and #8 are "floating"
8 x |channel and cannot be read (user error)

then FBDIMMs 7 and 8 connect to SMBUS and their
SPD can be read, but the "data path" is floating,
so the BIOS probe can't touch them. Neither can
the OS use them.

I won't give feedback on the usage of risers, unless
you find risers are present. It's the same idea, but
it will take me more drawings to illustrate what
to do. When the risers are plugged into 1,2,3,4 in
the above diagram, 5,6,7,8 FBDIMM slots on the motherboard
cannot be used (crash-ola if you do use them).

Paul

"Paul" wrote in message
news
Also, Task Manager shows 16 GB of memory as "hardware reserved":

https://i.postimg.cc/7LPp71Yg/Untitled-1.png

OK, now we're getting somewhere.

FBDIMMs don't work, if there isn't continuity in the channel.
Seaburg talks to first DIMM. First DIMM talks to second DIMM
in channel. If first DIMM in channel is missing, second DIMM
"floats" and the OS accounting system calls it "hardware reserved".

https://www.hardwaresecrets.com/how-...memories-work/

https://www.anandtech.com/show/2059/4

Check out page 179.

https://downloads.dell.com/manuals/a...uide_en-us.pdf

"You must remove the memory riser cards from the computer in order to
install memory on them. The memory slots on each riser card are
numbered
DIMM_1-DIMM_4. Memory must be installed on these cards in the order
that they are numbered; that is, DIMM_1 on riser card 1 must be
populated
before DIMM_1 is populated on any other card. DIMM_1 must be populated
on each card before DIMM_2 can be populated on riser card 1, and so on.
Memory must be installed in sets of four with one of the four on each
riser
card."

Thanks for that. I had actually found that document and researched it when I
originally upgraded the PC from 8 GB (4x 2 GB) to 32 GB (4x 8 GB) a few
months ago - and *then* discovered the built-in 16 GB limit of Windows 7
Home ;-)

But I thought once I upgraded to Win 10, that limit would go away
spontaneously.

I had the same idea as Yousuf: temporarily removing half the RAM, letting
the BIOS adjust to 16 GB and letting Windows discover this amount of memory,
and then adding the memory again. I did that a few minutes ago, and hit the
restriction that the PC will not boot, even to the BIOS screen, unless 4
DIMMs (or multiples of 4, presumably) are present. Grrr. I wonder where I
put the old DIMMs - I could put two of those in place of 2 8 GB ones and go
through the process that Yousuf describes. performance with mis-matched
DIMMs may be reduced, but it should at least boot.

I removed the two DIMMs from slot 1 of the riser cards 3 and 4, leaving just
the two in slot 1 of risers 1 and 2, so I complied with the first part of
the Dell instructions... but not that killer final sentence ;-)

If I find the old DIMMs, I'll give it a try and report back. I really
*don't* want to have to do anything that will upset a PC that seems to work
perfectly in Win 10 (installed apps seem to work), so that's why I'm being
hesitant about another installation/repair of Windows - if it works, don't
disturb it... But if all else fails, maybe I'll have to hope that a repair
from the Media Creation Tool will leave everything else untouched, or else
accept that if it doesn't, it's time to get out all the installation CDs etc
and do an inventory of what's installed, what browser passwords are
pre-saved (and then forgotten about) - and obviously save all user files off
the C drive in case of disasters. Which reminds me, I haven't backed up my
wife's PC for ages. I do mine most days, depending on what changes, but I
tend to neglect hers, partly because she's only just started using it again,
after needing a more powerful PC than her laptop for a new course that she'd
studying.

NY wrote:

"Paul" wrote in message
news
The BCD can limit memory.

https://docs.microsoft.com/en-us/win...ipulate-memory

In an administrator command prompt window, type this and check:

bcdedit

Usually, something like this isn't needed. This dumps "noise"
in the file.

bcdedit /enum

I would have thought MSConfig would be doing the same thing.
But maybe it's intended for boot.ini instead ?

The memory license for Win10 Home is 128GB, Win10 Pro is 2TB
(enough for an Epyc). You're right, that this should not be
happening - but what could be happening is the BCD values
were preserved on the upgrade install.

https://docs.microsoft.com/en-us/win...ndows-releases

Also, Task Manager shows 16 GB of memory as "hardware reserved":

https://i.postimg.cc/7LPp71Yg/Untitled-1.png

Perhaps from an unsupported hardware configuration. The Dell manual
that I found on the T7400 (noted with its URL in my prior reply) says
that the maximum memory capacity is 64GB (when using the risers), 32GB
without, which not the 128GB mentioned in Dell's spec sheet. Dell's
manual and their spec sheet don't match on what is the maximum memory
capacity and maximum memory module size. The manual lists up to a 4GB
max size per memory module, not the 8GB sticks you bought.

I've also run across low- versus high-density memory modules. Many
mobos and their BIOSes can only handle low-density memory modules. The
chipset on the mobo may not handle the memory architecture of
high-density memory modules. Even if your mobo's chipset can handle
high-density memory modules, don't mix low- and high-density modules in
your configuration. Back for computers as old as yours, high-density
modules had low compatibility with computers. Even if the seller
qualified his auction or product with a notice it was a high-density
module, users didn't know what that meant and were only looking at the
module's capacity. The low-cost high-density modules had low
compatibility. As I recall, the high-density modules had memory chips
on only one side of the PCB versus the low-density modules that have
memory chips on both sides. Back then, you couldn't give away high-
density memory to the educated users but you could sell it cheaply to
the typical user. They might have a disclaimer or tech details
somewhere to prevent buyers from returning the unusable memory.
High-density memory modules in a mobo whose chipset cannot support that
memory addressing architecture could only access half of the rated total
capacity of the module. The high-density memory modules appeared long
before the mobo chipset could support them. I'm not sure when Dell came
out with their Precision T7400. From some articles, maybe it showed up
around 2012. I don't remember when was the debacle of high-density
memory modules appearing before chipsets would support them, only that I
had to watch for this scam for my prior PC.

https://www.techrepublic.com/blog/us...-requirements/

I did find:

https://www.dell.com/support/home/us...driverid=kv78g

for a BIOS update dated back in 2012. Don't know what BIOS version you
have. I found that by using a search engine instead of hunting around
Dell's web site for BIOS updates. I happened upon:

https://www.dell.com/support/home/us...t7400/diagnose

I had to wait a l-o-n-g time for them to update their page. When it did
paint, I see the latest BIOS version is A11 (released 2012-06-28). If
you update the BIOS, also get their chipset driver package since it may
be needed by the OS to handle the memory through the BIOS that you
added.

Another possibility is you have hardware configured to suck up some of
the system memory. Are you using a video daughtercard or onboard video?
Onboard video requires it consume a portion of the system memory. It's
general slower than VRAM but cheaper, so the onboard video is configured
in the BIOS to steal away some of the system RAM. Check your BIOS
settings to see how much is allocated to the onboard video. Maybe it's
a percentage instead of a fixed amount. BIOS settings won't change
because you changed to a different OS. Other devices can be configured
in the BIOS to reserve system memory. That's an old mobo, so it has AGP
settings in its BIOS. Any memory reserved for AGP won't be available to
the OS. It should not have a 16 GB size choice but all those devices
that are allocated reserved memory in BIOS will add up.

Another possibility is the memory remapping function in the BIOS is not
enabled. It can be called memory remapping, memory extension, or
something similar. Some BIOSes are extremely basic (designed for boobs)
but some have tons of settings. You might just want to reset the BIOS
to an optimal or standard config and then revisit its individual
settings to see if you want to customize differently.

Run msconfig.exe, the Boot tab, click on Advanced Options button, and
check if the "Maximum memory" option is enabled. Don't see why you
would've enabled this before. Both the "Number of processors" and
"Maximum memory" optionsshould be unchecked. If you change these
values, you have to reboot to effect those changes.

What is reported and testable when you boot using memtest86
(https://www.memtest86.com/)?

Sometimes a BIOS update allows accessing more system RAM. The hardware
that is provided in a setup may outstrip what the old BIOS version will
support. That is, a newer BIOS is sometimes needed to unlock all the
hardware functionality (well, more of it). With that being an old
discontinued model, finding a BIOS update from Dell might be difficult.
You might have to call them to report your BIOS version (it's shown in
the POST screen) and ask if a later version is available for that model
(be sure to get the model number off the mobo, not for the entire
computer).

Um, you did check that each memory module was FULLY seated in its slot
(whether onboard or in a riser) and the risers (if used) were fully
seated, too ... right?

On 11/12/2018 7:33 AM, NY wrote:
My wife's Dell Precision T7400 PC has 32 GB RAM (I upgraded it recently
from 4x2GB DIMMs to 4x8GB DIMMs). It originally had Windows 7 Home
installed, and I know that this has a 16 GB limit, so I wasn't too
surprised to see in Control Panel | System that it reported "32 GB RAM
(16 GB available)".

Having just upgraded it to Windows 10 Home 1803 which has a much higher
max memory, I'm puzzled that Settings | System (and Control Panel |
System) still reports "32 GB, 16 GB available".

I've check MS Config | Boot | Advanced and the "Maximum Memory" box is
not ticked to enforce a lower limit.

What am I doing wrong? The PC clearly sees that it has 32 GB, right from
the BIOS config menu up to Control Panel | System. How do I enable
Windows to use the additional 16 GB of RAM?

I'd say do an In-Place Repair Install. It'll keep your data, settings,
and installed apps in place. It'll just overwrite the existing copy of
Windows with itself like a factory reset.

Repair Install Windows 10 with an In-place Upgrade | Tutorials
https://www.tenforums.com/tutorials/...e-upgrade.html

Yousuf Khan