RAM Clocking

[Jakal]

I've got a Shuttle Ak39N based on the KT400 chipset it supports 133/166/200MHz speeds for ram. The fsb only allows 100/133MHz for the processor. I've read of people using a 333 fsb by changing some jumpers but there's nothing stating the facts in the manual. My question is..
Could I underclock my PC3200 to PC2100 speeds?

The ram is new and offers a lifetime warranty, Patriot Signature Line Dual Channel PC3200 2x512Mb. I'm also wondering about the overall system performance. If ran at the same clock speed as the processor I should notice an increase in performance, right? I've also seen rigs who's cpu was at 266 and they had 333 ram. I'm just wanting some opinions and thoughts on the subject. Thanks

 

[Greg King]

Nice RAM. The RAM will automatically underclock itself to PC2100 speeds. Thats the beauty of RAM. It's the same thing as putting a stick of PC2700 and a stick of PC3200. The 3200 will underclock itself to the 2700 speeds. You have nothing to worry about.

 

[Jakal]

Thanks for the the help, I was hoping it would. I'll declock it then run my benchmarks again to see how better/worse I end up.

 

[Greg King]

There is no reason you should have to "declock" your RAM. You should just be able to put it in your system and it will set the timings to the acceptable speeds. Either way, you are good to go.

 

[Jakal]

Well I meant go from 400MHz to 266Mhz. Which I've done and am running stable now at effectively 2.2GHz.

http://photobucket.com/albums/c388/Jakal_Blu/Oveclocked/

I've rerun the benches and have found a noticeable increase all around except for the ram part in SiSoft. There's definitely a good overall improvement by having the timings at a 1:1 ratio. Ram is now a 2.5-2-2-6 which is fine. Temps have increased a few degrees but my Volcano 12 has no problem keeping them under 115F at load ~3000rpm.

 

[Jakal]

OK Quick question, I've had a brain fart and can't remember how the speeds work for fsb to cpu ratio... I was looking at some performance reviews of the Opty processors and found a guy who's gotten 10x300=3000Mhz.

If I'm thinking of this right.. The fsb is 150 x 2 (to get 300) x 10 the multiplier to get 3ghz? I know the fsb x2 gives you ram speeds and then the multiplier gives you the final clock speeds.. but that's slower than the original fsb.. ?

For my pc it's 147 x 2 = 294 which is the fsb. Then 147 x 15 for final core speed of 2.2Ghz. So following that model the fsb for the opty in question is 300mhz. Which would be 600mhz for the ram.. Now that's pc4800 speeds if I've figured this out right.

So if I were trying to get the same results I'd need to buy the pc4800 ram. Right?
Now I feel dumb....

 

[Rob Williams]

10 * 300 = 3.0GHz could mean many different things, depending on his memory. If he has a superb 1GB set, he may have:

FSB: 300MHz
Divider: 1:1 (Meaning 300MHz * 2 = DDR600, PC4800)
Multi: x10

Or

FSB: 300MHz
Divider: 9:10 (270MHz * 2 = DDR540, PC4320)
Multi: x10

Or

FSB: 300MHz
Divider: 5:6 (250MHz * 2 = DDR500, PC4000)
Multi: x10

At any rate, you should never have to 'de-clock' your memory. If you do, somethings seriously wrong with the modules. If you have DDR400 memory, you should be running them at least at 200MHz. If you are running them lower, you are slowing the modules down.

Edit: Doh, I didn't realize you were dealing with Socket A. Ciento likely knows more about that then anyone, but I think he's away for the holidays.

 

[madmat]

The modules should be set to 166 as the native FSB of that CPU is 166 so as you scale the FSB up the ram will be in synch with the bus.

 

[Jakal]

It's a 10x multiplier he states further in the review.. so it must be 300Mhz fsb. I was looking at getting the Opty 150 which has a 12x multiplier, and boosting the fsb to 250 would result in 3Ghz speeds without to much strain. I think the Zalman9500 would do nicely to keep the temps down.