Which Memory is Faster or Better?

[Oscar]

Hello-

Question: Which memory is faster or better? A 256mb
PC2700 DDR 333 NON-ECC memory, or a 512MB PC2100 DDR SDRAM
memory? And, please explain the difference.

My computer has a 256mb of PC2700 DDR 333 memory. I want to
upgrade the memory. I realize that I can't mix speeds, or
replace the existing memory with slower memory because it
would cause problems.

I will be grateful for any additional information you can
send.

Thanks.

[Alvin A Brown]

Hello

Well there is not much

One memory stick is fater than the other pretty simple. PC2700 is
much faster than your PC2100. It;s like comparing a A Ford Mustang
to a Porsch, am pretty sure you know which is faster.

Al


Oscar wrote:

> Hello-
>
> Question: Which memory is faster or better? A 256mb
> PC2700 DDR 333 NON-ECC memory, or a 512MB PC2100 DDR SDRAM
> memory? And, please explain the difference.
>
> My computer has a 256mb of PC2700 DDR 333 memory. I want to
> upgrade the memory. I realize that I can't mix speeds, or
> replace the existing memory with slower memory because it
> would cause problems.
>
> I will be grateful for any additional information you can
> send.
>
> Thanks.

[Wayne W.]

Depending on your motherboard, and if it supports Dual-Channel DDR
memory, you will get a boost from using the 256mb PC2700 DDR memory in
conjuction with your present memory if they are the same make and model.
I'll grant you, the benefit of Dual channel DDR is minimal, but if you
go backwards to 2100 memory, you will have a slower system. So, by all
means go with the 2700 DDR memory, and get the same stick as you already
have.


Wayne

> Hello-
>
> Question: Which memory is faster or better? A 256mb
> PC2700 DDR 333 NON-ECC memory, or a 512MB PC2100 DDR SDRAM
> memory? And, please explain the difference.
>
> My computer has a 256mb of PC2700 DDR 333 memory. I want to
> upgrade the memory. I realize that I can't mix speeds, or
> replace the existing memory with slower memory because it
> would cause problems.
>
> I will be grateful for any additional information you can
> send.
>
> Thanks.

[Jim]

I know this question was posted previously with not much response, so I
thought I'd give it a whirl!

The issue of 512MB vs. 256MB is a red herring here, after all, if you tell
me your system is constantly thrashing and banging the pagefile due to lack
of memory, AND you do lots of video and audio editting, heck, MORE MEMORY is
far more important than a slight increase in DRAM speed!

In contrast, if you tell me you do light office work, a few games, and
Internet browsing, your memory demands are probably nominal. You may in
fact gain NOTHING from going above 512MB total system memory, and assuming
you already have 256MB, another 256MB would be ideal and less wasteful
(spend the savings elsewhere). IOW, what's missing here is CONTEXT!

But for the sake of argument, let's take the issue of 512MB vs. 256MB off
the table, let's compare apples to apples, oranges to oranges. I assume the
reason you've indicated different MBs is because you're trying to decide,
dollar for dollar, does MORE MEMORY or MORE SPEED improve your system.

It would be helpful to have CPU and mobo details, but I'll have to makes
some assumptions for the time being. Let's say you have a 200/266 FSB
motherboard w/ support for 200/266/333 DRAM. And it's a given that PC2100
memory (133 MHz actual, 266 MHz DDR effective) is clearly SLOWER than PC2700
memory (166 MHz actual, 333 Mhz DDR effective). Let's also assume you have
an Intel P4 2.4 GHz 533MHz (133 actual) 512k Northwood CPU. All pretty
common, middle of the road components.

When you install the CPU and RAM into that mobo, you have the option of
running the system ASYNCHRONOUSLY or SYNCHRONOUSLY. The system is running
"sync" (1/1) when the CPU FSB and DRAM are operating at the SAME frequency.
In contrast, the system is running "async" when the CPU FSB and DRAM are
operating at the DIFFERENT frequencies. It has been shown emperically and
repeatedly that running "sync" produces better results, MHz for MHz, than
running "async". Running "sync" greatly reduces "wait states" in the
interaction between the CPU and memory subsystems.

When you decide to stick that PC2700 (333 DDR effective) RAM into that
200/266 mobo, you're running ASYNC (specifically, 4/5 divider, or CPU FSB =
133 / 4 * 5 = 166 actual, x 2 = 333 DDR effective). If instead you install
the PC2100 (266 DDR effective) RAM into that same 200/266 mobo, you're
running SYNC (specifically, 1/1, CPU FSB = DRAM)! How different motherboard
accomplish this varies, some will allow you to set the CPU FSB and DRAM
independently, others will provide the DRAM ratio or dividers setting (e.g.,
3/4, 4/5, 5/6), IOW as a percentage of the CPU FSB, while others provide no
solution AT ALL! You can only run SYNC! The only other option in this last
case is to overclock the CPU FSB, which then indirectly OC's the DRAM
(assuming the mobo will even LET you OC!). But that opens a whole 'nother
can of worms, let's put overclocking aside and stick to the simpler cases.

Here's my point, to assume that a FASTER DRAM is necessarily BETTER is
incorrect. You have to consider any memory choice in the context of other
components, the CPU, mobo, whether it provides DRAM ratio settings or can
set CPU and DRAM separately, and if not, can the CPU be overclocked so you
CAN exploit the memory. You might very well find that during performance
tests that exercise the INTERACTION of the CPU and memory subsystems,
running SYNC outperforms that same system running ASYNC, despite the DRAM
running at higher speed under ASYNC! Of course, there will obviously come a
point where the memory speeds are SO HIGH, even async beats sync. But even
though this is theroretically true, in practice, this is often moot, the
option is rarely available! Consider the mobo example I just used, with
200/266/333 DRAM support. If you DID try to go even higher speeds, say w/
PC3200 (200 actual, 400 DDR effective), THAT'S NOT EVEN SUPPORTED! Now
you'd HAVE to OC the FSB to fully exploit it! And unless you OC'd the CPU
FSB to MATCH the memory, you'd only be running async to-boot, for example:

CPU FSB = 133, DRAM = PC3200 (DDR 200):

Ex #1) CPU FSB = 200 w/ 1/1 divider (sync) = DRAM 200 actual, 400 DDR. (out
of this world OC and sync, nirvana!)
Ex #2) CPU FSB = 166 w/ 4/5 divider (async) = DRAM 200 actual, 400 DDR
(slight OC but async)
Ex #3) CPU FSB = 133 w/ 4/6 divider (async) = DRAM 200 actual, 400 DDR (no
OC but async, rare)
Ex #4) CPU FSB = 133 w/ 4/5 divider (async) = DRAM 166 actual, 333 DDR (no
OC but async)

I threw in the last example (#4) on purpose. I wanted to illustrate one
reason you might buy higher speed RAM, despite everything I said so far.
Namely, the higher speed of PC3200 in example #4 is UNDERCLOCKED, and
therefore provides some headroom, more stability compared to PC2700 (the
highest the mobo is rated to support). So here we have a case of YES,
recommending the higher speed, but NOT for the reasons of performance.
Nope, for STABILITY! The same concepts apply to PC2700:

CPU FSB = 133, DRAM = PC2700 (DDR 333):

Ex #1) CPU FSB = 133 w/ 4/5 divider (async) = DRAM 166 actual, 333 DDR (no
OC, but async)
Ex #2) CPU FSB = 133 w/ 1/1 divider (sync) = DRAM 133 actual, 266 DDR (no
OC, sync!)

IOW, ex#1 is probably what you WANT to do /w a PC2700 purchase, but ex #2
may be what you SHOULD do! Ex #2 *may* actually produce better results
because of sync. So the justification for PC2700 becomes the headroom, MORE
STABILITY. And if sync really is better in this scenario, and you frankly
have some quality PC2100 from Crucial or Corsair available or at bargain
prices, that stuff is so good to begin with, it probably can be overclocked
to PC2700 anyway! IOW, the quality of the PC2100 product is already giving
you plenty of headroom. The Crucial/Corsair PC2100 turns out to be a STEAL
for your purposes, everything else is money down the drain. Now, if you
have *CRAP* memory from Joe Blow's World of Generic Memories, yeah, I'd say
I'd be lookin' for some PC2700, just as a precaution.

Just as an aside, this explains why so many oveclockers are enthralled w/ a
board like, say the Abit BH7 (
http://www.excaliberpc.com/product_info.php?cPath=181_220&products_id=1544 ).
Everybody and their uncle KNOWS that board is intended to support 800MHz
FSB, but Abit can't SAY IT without getting into a licensing scrap w/ Intel,
and at HALF the price of the Canterwoods. Though the board officially only
supports 200/266/333 DRAM and CPU FSB 133 (quad-pumped), all the OC nuts are
stickin' their (now old) P4 533MHz Northwood's in that thang, some quality
PC3200 RAM, then OC'ing the CPU FSB to 200MHz (that a 50% OC mind you, and
many a P4 seems to handle it). So now they have their CPU and DRAM running
200MHz actual, 800MHz DDR effective, without having to even resort to the
new Intel 875P mobo which OFFICIALLY supports the new Intel 800MHz CPUs!
Plus it's SYNC. The only place they fall short is perhaps dual-channel.

To summarize, it's impossible for ANYONE in this forum to claim one DRAM
module is better than another based on SIZE or SPEED without context, nor
without considering all the options available to you, including CPU, mobo,
OC'ing ability of the componentrs and your WILLINGNESS to consider OC. Give
me ALL the details, tell me how you want to use the system, tell whether you
want to lean more towards performance or stability, tell me how much you're
willing to spend for the right components, whether you will OC if necessary,
etc., and I may be able to give you a specific answer.

Oh, and one last thing, mixing memory speeds is foolish, since the memory
will only run at the slower of the two anyway, it's just wasting money.
Better to dump the current stuff and buy a matched pair, esp. if you intend
to go daul-channel at some point. Mixing can also introduce weird problems
that are just better left alone. So either trade up by selling what you
have, or match what you already have.

JMTC, HTH

Jim




"Oscar" > wrote in message
...
> Hello-
>
> Question: Which memory is faster or better? A 256mb
> PC2700 DDR 333 NON-ECC memory, or a 512MB PC2100 DDR SDRAM
> memory? And, please explain the difference.
>
> My computer has a 256mb of PC2700 DDR 333 memory. I want to
> upgrade the memory. I realize that I can't mix speeds, or
> replace the existing memory with slower memory because it
> would cause problems.
>
> I will be grateful for any additional information you can
> send.
>
> Thanks.
>
>

[Kevin]

No point in using PC2700 if your cpu runs on 266fsb,you aint goin to make it
any faster.

[Wayne W.]

> No point in using PC2700 if your cpu runs on 266fsb,you aint goin to
> make it any faster.

Not true if you overclock.