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A few simple RAM clocking questions

O

octbit

n00b
Joined
Nov 3, 2005
Messages
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I'm new to A64 OCing and have been catching myself up on the requirements and effects of overclocking this architecture. If I'm understanding it correctly, the "best" method of OCing these chips is to step up the HTT/FSB without having to set a RAM divider. However, since I'm running DDR400, I don't believe I'll have a lot of room. I'm reading about the ~2.6 OCs other Opteron 170 owners are getting, and am wondering how they're achieving this.

In these scenarios, are you guys just saying, "divider be damned, I want the best OC I can get"? Is there something I'm missing? Are RAM dividers somehow avoidable without using higher spec RAM? Is running your RAM "out of synch" really that bad?

Right now my CPU is running at 22C idle and 30C under max load... it seems to be crying out for a higher clock, and I just want to make it happy :)

Thanks in advance for any help!
 
Not true. The "best" oc is getting the highest cpu mhz, while maintaining as close to the highest ram speed, using a divider on the ram as not to run it too fast and limiting the cpu speed.

Cpu mhz is what you're after. If you can get a bit past 200mhz on the ram, it's a small bonus, but does not translate to any real world performance increase.

If I had to limit myself to 1:1 ram/htt....my oc with this current ram would only be 1.98ghz, instead of 2.9ghz :D
 
Interesting - so just to make sure I have this straight, using a divider does not cause the CPU to "wait" on the RAM as some articles/posts I've read suggest? No negative benefit as long as your effective frequency is still at or above stock speeds?

In the meantime I managed to run Prime95 for an hour and a half without problems with the following:

240(fsb) x 10(cpu mult) = 2.4GHz 1.40v

I dropped HT mult. back to 4x and put the RAM on a 5:6 divider. I've tried a 250MHz FSB on 1.40v and 1.45v. The first died on boot, the second after running 20 minutes or so of Sandra benches. 1.5v seems high for 2.5GHz based on other's results, but I'm going to fire it up here in a second and see what happens. It would be a nice milestone because it would put both the RAM and HTT almost perfectly in line with spec speeds given the multipliers/dividers I'm using.

Thanks for your help!
 
That's more like it. Using a ram divider has no ill efeects like the nf2 boards did. And since the memory controller is on the cpu, the stock "200mhz" is actually a divider of the cpu speed as well.

As far as running 1:1 and getting a huge performance increase.....there is none except in synthetic benchmarks....superpi really likes high mem speed. I wasted the better part of 18hrs proving this to myself, as it didn't "sound right" after just switching from an axp barton chip. Running ram at 240mhz resulted in 1-3 seconds increase in mp3/video encoding and 3d rendering, but virtually no increase in fps playing games.
 
Maybe this will help. It's my settings

Abit av8 (FSB 254)
Corsair 3200 Ram (333) allows it to overclock ~425
Opteron 170 (multiplier 10 vcore 1.35)
LDT x 4

Second option
FSB 280
Ram 133 (slight underclock) looser timing from 2.5/3/3/8 to 3/3/3/8
opteron 170 (multiplier 10 vcore 1.475) I wouldn't go over 1.5
LDT x 1

Does your 170 show Dual channel or single channel mode? Mine might have a bad memory controller as it only runs single channel.
 
scwam said:
Mine might have a bad memory controller as it only runs single channel.
Click to expand...

I'm not familiar with that abit board, but maybe the 2nd stick of ram is in the wrong slot?

And you might try bumping vdimm up a notch or 2. (2.7 - 2.75 is generally pretty safe....go higher only if you have some airflow over the dimms) That might make the ram stable. My corsair 1gb sticks were good to ~240-245 iirc.
Another option if it's available to you, is give the chipset a boost in volts as well. Generally no more than 1.6 is needed (1.5v is stock)
 
SpoogeMonkey said:
That's more like it. Using a ram divider has no ill efeects like the nf2 boards did. And since the memory controller is on the cpu, the stock "200mhz" is actually a divider of the cpu speed as well.
Click to expand...

Good news. I guess I had found some dated information on Memory dividers.

I'm going to keep my fingers crossed on this 2.5GHz OC. Thanks again for all your help!
 
scwam said:
Does your 170 show Dual channel or single channel mode? Mine might have a bad memory controller as it only runs single channel.
Click to expand...

Dual channel. I'm running in slots 1 and 2, IE right next to each other rather than spread across two different banks like my old P4 875 board.

Thanks for your settings. Looks like your chip is already handling much more than mine at stock voltages, though. I might try bumping my chipset voltage +.1 as Spooge suggested to see if that's where I'm falling short as opposed to my CPU.
 
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