Need some overclocking help with a San Diego based rig...

H

hemi

Gawd
Joined
Mar 9, 2000
Messages
685
Hey,

I need some help here. I’ve been overclocking for about 8 years now and have had some pretty kick ass systems, so I’d like to think I at least have a clue. My latest rig is giving me fits and I’d like to get some opinions on where to throw the money next.

The config is this:

A64 3700 – San Diego
2x512MB PDP ‘Patriot’ PC3200LL
ASUS A8N-SLI Premium
XFX 7800GT
Antec TruePower II 480

Everything was new except for the CPU. I bought it used. The prior owner claimed to have had it stable at 2.8GHz on a DFI board with ~1.65v (IIRC), with the HTT around 300. I believe that he did, only because when I first bought it a few months back I was able to get it up near 2.7GHz with some stability at ~1.58v. That was on ‘quiet’ air using a Zalman CNPS-7000Cu at 7v. The problem was that getting there was a hell of a challenge, as even hitting 2.4GHz was tricky and I had to tweak the shit out of the memory timings to get it to boot anywhere above stock.

Keep in mind I’m not looking for max overclock here. If I can get it up near 2.5-2.6GHz, I’ll be satisfied. That said, I just finished a water cooling setup that keeps it cooler and even a bit quieter. Now I can’t get the friggin thing to POST above stock no matter what I do. I can keep the RAM timings tight at 2-3-2-5-1T when stock, and the CPU idles at 29C and peaks under load at 36C (22C ambient), so I know the cooling loop is getting the job done. (Storm, D5, BIP X-flow, etc.)

What the frick should I do? Is it the memory controller(s) in the CPU? The RAM? The board? I’m just at a loss at what to try next, and I don’t have any other parts of this caliber to test with. I’ve also tried pulling a stick of RAM and had a little more success, but nothing that one would consider fully stable.

EDIT: Wanted to add that my HTT seems capped around 240-245...



I’ve got my eyes on a new Opteron 165…should I go for it?


Thanks in advance!

Tom
 
OK, so just to try and prove I'm not a moron, here's what I've done tonight...

Tried easing the HTT up from 200. Seems to hit a wall over 220. 11x220 works fine.

I tried as low as 8x230, RAM set to 200 (CPU/22) at 3-4-4-8-2T. Set RAM voltage anywhere from 2.8 to 3.0v (tried several times). CPU at 1.55v in BIOS. It will POST at 230, but won't boot into Windows. I tried bumping the HTT to 1.25v and the chipset to 1.6v, but nothing.

I also added a Zalman fan bracket and a 92mm Nexus fan to blow directly on the heatsink attached to the power FETs and the heatpipe for the NF4 chip. Using my old Omega digital thermometer, I whipped up a thermocouple and held it against the heatpipe block on the NF4.

Before the fan: 48C
After the fan: 38C

Granted, the thermal interface was crap (just touched the thermocouple to the block), but it still shows an improvement, although nothing in the way of an OC gain.

What should I do?!?!?! Thanks.

Here's a pic of the setup:

rig_oc_prob.jpg





Thanks again,
Tom
 
Alrighty, I guess I'm fooked. I'm gonna try and see what the RAM really likes by bringing everything else down. Of course I'm not expecting this RAM test to do much of anything, because if I truly have a hardware problem, it's most likely one of the three I mentioned above, and all have an impact on memory performance (or lack thereof).

Then I start replacing parts. :mad:


Later,
Tom
 
OK, making some progress now.

I started using clockgen and screwing with the HTT to find what this RAM actually likes. It tops out at 225MHz @ 2.5-3-3-7-1T with 2.75v. I tried higher voltages and it did nothing. Fine, memory capped out, and this is actually better than I thought it was capable of.

Next up, getting the CPU/RAM dividers figured out. Here's where I stumbled upon something interesting. This sucker will only work if the divider is at 333 or 400, which I believe should be 5:6 and 1:1. 400 is definitely 1:1. The 333 setting seems to vary depending on CPU multiplier. I'll elaborate a bit later, but regardless, it won't do a damn thing if I'm at 266 or 200. This is where I got myself into trouble. I lowered it as low as possible and loosened the timings a lot in an attempt to keep the memory out of the equation while trying to find the max CPU clock. In doing that, it back-fired and kept me from figuring anything out. Anyone know why this is the case? Unfortunately, it limits the amount of tweaking I can do to find the ceiling for the CPU.

So, that said, I put the RAM divider at 333, HTT at 4x and went at it with clockgen again. I took the HTT all the way up to 280, which topped out the RAM at ~224. I think it would go even higher, but none of the other dividers will work. Also, to elaborate on the 333/5:6 ratio theory a bit more, if it was truly 5:6, the RAM would be at 233 with the HTT at 280, but it isn't. Now according to A64 MemFreq, if I take the CPU multi to 10x it would be...but then at 11x, it drops back to 220. I admit that I haven't read a whole lot as to how the RAM dividers work with the A64's, but can anyone tell me why that is?

At this point, I think I'm gonna shoot for 10x270, divider at 333 to put the RAM at 225MHz and leave the HTT multi at 4x, since it seems just fine at 280. I'd love to shoot for an HTT of 300 just for fun, but with this RAM I'd have to drop the CPU multi all the way back to 6 to get there. With the 11x multi, I can walk it up to 285-290 before the RAM hits its ceiling.

I realize this thread isn't seeing much action, but hopefully all this babbling helps someone else out there who might stumble across it. I'll post an update when I get it fully tweaked.


cpuz1.gif


cpuz2.gif



Thanks,
Tom
 
Could it be that the mem controller on that chip isn't that great?
 
Hey,

Yeah, I guess that's a possibility. Still thinking about an Opteron 165, or possibly going with a 2x1GB set of good RAM. Can't decide now. :D

Here's where I have it now:

HTT Multi: 4x
HTT Voltage: 1.25v
HTT: 270MHz
RAM Div: 333
RAM Voltage: 2.75v
RAM Clock: 225MHz
CPU Multi: 10x
CPU Voltage: 1.55v (overvolts between 1.56-1.58v)
CPU Clock: 2700MHz

cpuz3.gif


cpuz4.gif


I'm going to run Prime95 overnight to see if it's stable here. I'll probably leave it as is until I get a new CPU and/or RAM.

If anyone has any other thoughts, I'd love to hear them...though I'm sure many have been down this path before and it's a boring topic now. :)



Later,
Tom
 
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