Help newb with basic memory query :o)

[sniper007]

As some may have seen in another thread, I am a newb to SFF pcs and building from scratch generally. Despite this, I managed to get my new Shuttle XPC SB95P up and running over xmas with no probs.

I am also a complete newb to OCing and this week have been tinkering and running a lot of benchmarks etc. I have settled on an overclocked FSB of 200 to 217. (3.4ghz to 3.7ghz) I have ran tests and so far this seems completely stable under load and temps are fine. 220 FSB is unstable however.

My query is with regard to memory. My MOBO will run at 533mhz and hence I bought Corsair DDR2 value select 4200 533mhz ram (2x512 paired).
In increasing the CPU clock FSB to 217mhz, have I increased the MOBO 533mhz and hence RAM and GPU as well? I noticed in the BIOS system memory frequency is set to 533mhz but has the option to go to 400mhz or AUTO. Do I need to put it on AUTO to stop it being locked at 533mhz and benefit from the increased FSB? Or does it not work this way? What is recommended? I just want to play wiht memory next as have obtained higher FSB. Want to do memory next then graphics.

My memory timings are also 4 4 4 12. Should I be looking to change these to lower more agressive settings? I read an article saying that ddr2 is in fact very good at still maintaining high speeds whilst keeping fairly loose settings such as the above.


Kind regards for any help. You have been most helpful so far with everything.

[Archaon]

Oh hell here we go...


1. You won't get the motherboard to run at 533MHz so don't even bloody try. Think about it...the multiplier for a 3.4GHz P4 is 17. 533MHz by 17 is over 9GHz. :eek:

2. Divide the FSB speed on a P4 by 4, and the DDR speed by 2...this gives you the actual speed (eg your P4 has a bus speed of 800Mhz, but in the BIOS it's 200MHz). The memory has to run in synch with this (unless you say otherwise). So really your memory is rated to run at 266.5MHz.

3. Because the RAM is in synch (probably not correct term but screw it), unless you tell it otherwise, if you FSB is set at 217MHz then your RAM will run at 217MHz as well because they run in a ratio of 1:1 (CPU:RAM) by default.

4. The ratio of 1:1 mentioned above can be changed however the result always puts the CPU speed higher (eg 3:2, 5:4)...and since you have PC4200 there is no point in doing this. Usually results in the RAM being slower anyway so it's not usually worth it unless you want to test your CPU. As such "Messing with memory" is limited to changing your FSB, CPU:RAM ratio and timings. And I don't know crap about timings so I'll leave that be.

5. Not all motherboards are great for overclocking, even if you can set insane FSBs like 533MHz in them. It may be that your motherboard won't let you go past 220MHz regardless.

[sniper007]

Oh hell here we go...


1. You won't get the motherboard to run at 533MHz so don't even bloody try. Think about it...the multiplier for a 3.4GHz P4 is 17. 533MHz by 17 is over 9GHz. :eek:

2. Divide the FSB speed on a P4 by 4, and the DDR speed by 2...this gives you the actual speed (eg your P4 has a bus speed of 800Mhz, but in the BIOS it's 200MHz). The memory has to run in synch with this (unless you say otherwise). So really your memory is rated to run at 266.5MHz.

3. Because the RAM is in synch (probably not correct term but screw it), unless you tell it otherwise, if you FSB is set at 217MHz then your RAM will run at 217MHz as well because they run in a ratio of 1:1 (CPU:RAM) by default.

4. The ratio of 1:1 mentioned above can be changed however the result always puts the CPU speed higher (eg 3:2, 5:4)...and since you have PC4200 there is no point in doing this. Usually results in the RAM being slower anyway so it's not usually worth it unless you want to test your CPU. As such "Messing with memory" is limited to changing your FSB, CPU:RAM ratio and timings. And I don't know crap about timings so I'll leave that be.

5. Not all motherboards are great for overclocking, even if you can set insane FSBs like 533MHz in them. It may be that your motherboard won't let you go past 220MHz regardless.



Thanks very much for your reply. Have to say Im a little confused, but thanks though.

Please, What I do not understand is this:

My default RAM timings are 4 4 4 12.
If I attempt to lower these at all the system wont boot. This is the case when the system memory frequency is at the default of 533mhz OR on AUTO.
However, when I select 400mhz as the system memory frequency, (the only other available option) I can boot with lowered timings (3 3 3 9) ?

Apologies, I just wish to understand this as fully as possible.


Regards

[Cable Monkey]

When you set the fsb to auto or native then you are running your memory at 533 fsb and the default timings apply. When you set to 400 fsb you are effectively underclocking your memory and thus you can tighten the timings.

[Archaon]

You shouldn't be able to select the memory frequency just the CPU FSB speed and the ratio of FSB:RAM...?

[cool_dude]

hmmm why get a shuttle for overclocking? :confused:

[Cable Monkey]

You shouldn't be able to select the memory frequency just the CPU FSB speed and the ratio of FSB:RAM...?
Some bios's let you select the frequency to run at. I got a mates pc to run stable by asking his mobo to run its ddr400 at ddr333. Cured the problem.

hmmm why get a shuttle for overclocking?

You get a Shuttle becuse you like them. If you can then overclock it is a bonus.

[Archaon]

*thinks ratios are easier* :p