Big difference between 250mhz at 1:1 and 250mhz at 5:4?

[hurrikaane]

My new setup will be either the Asus P4C800 or the Abit IC7-G. In real world terms (and not just synthetic bench's), would using DDR500 and a FSB of 250mhz at 1:1 really deliver that much more performance than DDR400 at 250mhz with 5:4? Cost is an issue, so I'm looking for a high level of price/performance.

PS to put it succintly, I'm trying to decide between a gig of OCZ 3700 Gold/Corsair 4000pro and some Corsair 3200pro.

 

[sman789]

http://forums.anandtech.com/messageview.cfm?catid=28&threadid=1129590&FTVAR_MSGDBTABLE=

 

[hurrikaane]

That thread mostly argues the difference between memory timings, ie cas 2 vs 2.5 vs 3. So assuming cas 2, how large is the difference between 1:1 and 5:4?

 

[Jeff7181]

Originally posted by: hurrikaane
That thread mostly argues the difference between memory timings, ie cas 2 vs 2.5 vs 3. So assuming cas 2, how large is the difference between 1:1 and 5:4?

At the same clock speed, there will be a noticeable difference... however, the main reason people run 5:4 is to allow a higher overclock... some people are using a 275 Mhz FSB... the only RAM that has a chance at running that fast is VERY expensive... so instead, they use a memory divider to allow the same FSB and same internal clock speed without spending a fortune on RAM.

 

[hurrikaane]

So I suppose the question then is if the $115 price difference between the OCZ 3700 and the Corsair 3200 is worth it in performance terms .. ie how "noticeable" is that difference

 

[Jeff7181]

I'd have to say no if that's for ONE "stick" of RAM... since the P4 only gets enough memory bandwidth from dual channel memory.

 

[hurrikaane]

I'm referring to 1 gig of ram (2 x 512).

 

[FPSguy]

Depending on the application, the difference in speed is in the range of 0% - 4%. See this article ("As for using DDR500 SDRAM in the synchronous mode during FSB overclocking to 250MHz, we really doubt that it makes sense. This overclocker memory is much more expensive than ordinary DDR400 SDRAM, while the performance it provides is just a little higher than that of DDR400 SDRAM with 2-2-2-5 timings. The table below shows what difference between these two combinations exists in various applications.").

Per this article, your first goal should be to max out your FSB. Then you worry about the RAM. Let's say you think you can get your bus to 275. It's unlikely you will find affordable memory with decent timings that will run at that rate. So, you will want to go to a 5:4 ratio, putting the memory at 220. That means you either want PC3500 (hoping it overclocks slightly), or PC3700. If you only intend to run your bus at 250, then the price of the PC4000 memory (not to mention the usually poor timings) probably won't be worth the marginal, if any, gain in speed you will get, and it would give you a better price/performance ratio to buy PC3200 memory with good timings. If you are talking about a P4 2.4C, though, you probably can get the bus higher than 250 and so you may want memory a bit faster than PC3200.

 

[hurrikaane]

Good info there. Basically what I've seen is that I can run the OCZ at 260 1:1 CAS 2.5, or the Corsair can run at 250 5:4 CAS2. The former is likely faster, but worth the extra cost? Perhaps not.

 

[oldfart]

Not at all worth the extra cost. The difference is negligible. Run 5:4 @ tighter timings and save some money.

 

[hurrikaane]

What are the timings on your memory in your system Old?

 

[oldfart]

2-2-2-6

 

[hurrikaane]

If your FSB is at 255 how'd you hit 3300 mhz? I'm new to this so my knowledge of the equations isn't so good.

 

[oldfart]

2.6C = 13X multiplier

13 x 255 = 3.3 GHz

 

[hurrikaane]

Ahh! Thank you forgot the multipliers ramped up.

 

[Soulkeeper]

when i buy memory i usually try to buy the best quality and speed i can find
with that said i would suggest something like pc3500 or higher for a hardcore user

 

[orion7144]

Originally posted by: hurrikaane
What are the timings on your memory in your system Old?

I know some people don't agree with me on this but throught my testing I have found that even if you use the faster ram with slower timings there is hardly any loss in memory performace vs using slower memory with faster timings. I am talking purely about the 865/875 chipset boards and not the AMD stuff.

Another note: The 2.4C at >3gig is extremely fast and keeps up if not surpass the newer CPU's. It does not mater if you are running 5:4 or 1:1. "Feel" wise you would not notice a difference only in the benchmarks.

 

[bjc112]

Originally posted by: oldfart
Not at all worth the extra cost. The difference is negligible. Run 5:4 @ tighter timings and save some money.

Exactly... No need to cash in all your chips for PC4000...

Get some PC 3500 run a 250-275FSB on the 5:4 no problem.

 

[hurrikaane]

I really like Old's setup. A 2.6c at 3.3 ghz with his DRAM running at 2-2-2-6. Seems like the best of both words: high CPU/FSB times AND speedy RAM timings - at a low price. My only concern is if the stock Intel heatsink will be able to handle that. My case will be a Sonata, which I hear does well in keeping the air flowing (with the 2nd 120mm fan).

 

[orion7144]

Originally posted by: hurrikaane
I really like Old's setup. A 2.6c at 3.3 ghz with his DRAM running at 2-2-2-6. Seems like the best of both words: high CPU/FSB times AND speedy RAM timings - at a low price. My only concern is if the stock Intel heatsink will be able to handle that. My case will be a Sonata, which I hear does well in keeping the air flowing (with the 2nd 120mm fan).

The stock HSF that comes with the Retail P4's is fine. The 3.0 and above (may be the 3.2) comes with a HSF that has copper.

 

[oldfart]

3.3 GHz is too high for a stock HS/F. The stock is good for ~ 2.8 GHz and not much more.

 

[Pentium]

My P4 is running 2.98 on stock cooling.

 

[oldfart]

3 GHz is pushing it. He is looking to go to 3.3 GHz. Way above what a stock unit can do, especially if a little extra Vcore is used.

 

[FPSguy]

Originally posted by: oldfart
3 GHz is pushing it. He is looking to go to 3.3 GHz. Way above what a stock unit can do, especially if a little extra Vcore is used.

I don't think 3GHz is pushing it for a 2.4C on stock cooling. Mine hit that easily with stock cooling. In the Overclockers.com database quite a few people hit 3GHz and above with stock cooling, and several hit 3.3GHz and above.

Originally posted by: hurrikaane
Good info there. Basically what I've seen is that I can run the OCZ at 260 1:1 CAS 2.5, or the Corsair can run at 250 5:4 CAS2. The former is likely faster, but worth the extra cost? Perhaps not.

Per the first article that I cited, the CAS rating, standing alone, is not all that important ("Note also that the CAS Latency parameter alone does not influence the memory subsystem speed too much. Two other parameters, namely RAS# to CAS# Delay and RAS# Precharge, affect the results much more heavily.").

Also, I think this comment focuses too much on the memory. You are talking about a 260 bus versus a 250 bus (a difference of 120 or so in the final speed of your processor). That is an important factor. And, a P4 2.4C might very well hit a 270 bus or higher with stock cooling (the average in the Overclockers.com database is around 275). So, maybe your best option would be to get a 2.4C and run the OCZ at 5:4 (275 FSB / 220 memory) and tight timings, or get some PC3500 or 3700 RAM of a different make and run it at 5:4 with tight timings.

 

[hurrikaane]

The OCZ I was referring to was the 500mhz version, which can't really be run at 5:4 since that'd be beyond the capability of the board (312mhz). I like the idea of running the 400/433 mhz stuff at 5:4, since that gives you 250/270 (thus 3.3-3.5ghz). That's pretty ideal, given than the Corsair has been shown to be able to run in real-world tests at 2-2-2-5.