Need advice on memory compatibility & performance

[Dunno1]

Hi Everyone!

I'm considering buying a new computer for home, and I need some advice on RAM issues. I'm planning to purchase a MSI P965 Platinum motherboard with a Pentium 4 820 processor (2.8 GHz / 800 / 2x1 MB), however, I don't really know what type of RAM should I buy for this configuration.

What I know is that I must buy DDR2 modules, but it's unclear for me what frequency the modules should have. As far as I see the 800 MHz modules are the fastest the motherboard can support, but I'm not sure whether the processor is able to handle and/or take advantage of these speeds, too. So, my first question is: should I buy 800 MHz modules or better stick with cheaper 667 or 553 MHz variants? Will the 800 MHz modules give me any additonal real-life performance over the slower modules?

The other question I have is about the module latencies. I've so far seen several CL5 800 MHz-es modules in catalogs, but actually no faster (CL4 or CL3) ones. Does this mean that all DDR2/800 modules run with CL5, or are there CL4 or even CL3 variants available? And if yes, do these - probably far higher priced - modules offer any real (>10%) performance advantage in desktop/gaming systems over their CL5 countersparts?

So, these are my questions. Hope some expert here can help and answer them in a few sentences. Thanks for your help in advance.

 

[HYST3R]

first thing i would recomend if you have not already bought the processor, go with a 9xx Petium series they are on a 65nm process and are way better processors for the same price. and since you have a 965 chipset you might want to consider a core 2 duo.

with that out of the way, you will want to get the fastest memory modules with the lowest latencies. 800mhz ram will yield better results than 667 or slower memory but isnt necessary. check out your motherboard handbook to see which modules are supported by your board, there should be a list of brands with speeds. there are cl4 800mhz ram modules but they cost considerably more and yes are faster. so its all based on your wallet really. the best way to go is get the fastest ram your mobo supports (800mhz) and then get the lowest timings you can afford.

 

[HYST3R]

im not sure where you are looking/shopping for ram, but there are a couple of really good sites with a plethera of choices for this selection of ram.

http://www.newegg.com/Product/ProductList.asp?Category=17&N=2010170147+1052108080+1052416064&Submit=ENE&SubCategory=147

www.newegg.com is a great one

www.tigerdirect.com is also a good one.

 

[Dunno1]

HYST3R, thanks for your fast and extensive reply.

As for the 9xx series - they unfortunately cost +50% more than their 8xx counterparts, and Core 2 Duos cost even more. So, I think will have to stick with the latter ones, as I don't think I can get out +>50% more performance out of the 9xx version.

As for the frequencies - the only thing the motherboards manual says is that it support 800/667/553 MHz modules, and that I can use any of these modules with a 800 MHz FSB processor (like the 820).

If CL4 modules cost so much more, I think I'll have to stay with the CL5 ones. Same thing as with the CPU.

Thanks for the links too, but unfortunaltely I live in a "less blessed" part of the world, so, ordering from internet shops outside of my country is not really an option for me (and I would probably loose any savings due to the huge shipping costs anyway).

So, thanks again for your comments. They helped me a lot.

 

[Dunno1]

One more question: Could a 667 MHz CL4 module work actually faster in real-life than a 800 MHz module but with CL5 ? Or does the CL level only matter between modules with same freqs?

 

[Mondoman]

Here is a post on latency and throughput that should be helpful: http://forumz.tomshardware.com/hardware/modules.php?name=Forums&file=viewtopic&p=1233230#1233230

In your case, the Pentium D processor has an 800MHz (effective) FSB. Due to the CPU's design, memory transfers go through the memory bus, memory controller, and FSB to/from CPU. Thus, the throughput limit is capped at 800MHz. Assuming you are running in dual-channel mode (pairs of identical DIMMs, one in each channel socket), even DDR400 will fill up the FSB (200MHz memory bus x2 for DDR x2 for dual-channel mode = 800MHz effective throughput). So, any memory from DDR2-533 on up will be fine and you won't see any big gain from going faster. Just buy the cheapest decent-quality memory you find (note that DDR2-667 may be cheaper than DDR2-533; if so, no problem, as you can always run memory slower.).

 

[Dunno1]

Thx for your reply, too.

I've also just read some tests, and they said the same thing like you, that with Intel processors RAM clocks don't really matter (you won't get higher effective performance with a 800 MHz module than with a 667 MHz one), unlike in the case of AMDs new cores, whose performance heavily depends on the memory clocks.