Passive Opteron anyone??

[Hesky82]

Before I pulled my 146 out of my system I wanted to see how flexible it was and had a go at undervolting the chip at stock speeds and managed to reduce the voltage to just over 0.9v with it still being prime stable at 2ghz.
At the time it was still cooled actively by a heatsink fan and I didn’t take note of its load temps. Now its been replaced by my dual opty I've been contemplating the feasibility of using it in a silent htpc running xp mc passively cooled with a single case fan providing airflow.
Has anyone cooled an undervolted a64 cpu passively before?
Would be cool to get some input.

Cheers

 

[Hesky82]

No heat sink at all!! The man must have been crazy

Mr Mister that’s pretty helpful, I guess those vapochill micro hs are pretty efficient!
It defiantly seems feasible.

 

[Hesky82]

Sandmaster500, that’s a good point! the ninja hs is huge and not really an option for me as I will be using a very slim case. I can probably pull the vcore down to around 0.8v and run it around 1.8ghz, speed isn’t essential as I'm only going to be encoding tv and playing back hdtv video. Im sure a decent Thermalright will do the job.

thanks for the replies guys.

 

[Hesky82]

http://img375.imageshack.us/img375/2168/passive0cv.jpg

Heres a quick screenie, gets up to about 42c

sure the cpu fan speed signal lead didnt just come unconnected from the mb

42C running 1.55volts passively is damn good!

 

[Hesky82]

just out of interest what is the lowest vcore an a64 cpu can run at before it will not post?? surely there is a point at which it will not clock at all, or the mc has not enough juice to function.
say for example you could go as low as 0.4v and it would still manage to clock at 600mhz or so lol
completely pointless I know but I’m still interested

cheers

 

[Hesky82]

yeah i cant go lower than 0.8v on my dfi mb, have a feeling it will post but not run at all stable at stock speeds

 

[Hesky82]

With stock vcore and high bh5 style ram voltage, as with the mem controller beinig on the chip, a % of the ram volts goes through the cpu (as far as i remember)

that is correct, I've only ever seen this happen with excessively hi ram voltages. the difference in vcore voltage is only slight compared to the amount we see some people run these CE6, UTT and BH5 ram sticks.

anyway clint you should know, you undervolting your 146 successfully, heck you were the guy that put the idea in my head and got me experimenting lol so if it goes wrong I'm gonna blame you
na I'm just gonna be running some low voltage generic ram on this htpc system, much the same vdimm I run my uccc sticks at, around 2.5volts

cheers

 

[Hesky82]

Haha, well...I did just sell the brother of your FPAW (for a premium price) with the help of both that screenshot with 2.0GHz @ 0.99volts and another with 3.1GHz @ 1.475volts...sure is a amazing performer.

its sad but I cant part with mine

Big.Wayne you completely forget about case cooling, a good case will draw a decent flow of cool air over the cpu cooler and prevent the cpu from thermal run away, just gotta make sure the vcore is low enough and cooler has a good enough C/W efficiency.

 

[Hesky82]

the fit of the ihs over the cpu core is probably questionable, seems to be a lot of amd 64 cpus that have poorly seated heat spreaders or with unevenly applied thermal compound between the core and ihs. could always take it off

 

[Hesky82]

of course temps play a big part, but do you know if your epox likes playing with high fsb, have you dropped the multi and pushed the fsb any higher to see if your mb is limiting your overclock?

Yes taking a knife to a cpu is never going to be a pleasant proposition, my 146 seem to run so very cool but this 170 dual runs a good 5c on load higher, I know its holding my overclock back but I still cant bring myself to cut the ihs off.