Getting It Past 3

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I waited long enough.

I got myself an 845PE motherboard (and Albatron 845PEV Pro, to be precise), and a CPU that I knew had to be a C1 stepping CPU (a 2.66GHz, week 35 Malay chip).

A Few Words About The Albatron

This board is small! It’s at least an inch narrower than the typical ATX board. Others have previously commented that things are a bit cramped and certain things are put in odd places. This is true. For instance, my Radeon 9700 Pro clears the memory slot by, oh, about a millimeter.

About an inch away is the edge of the Memory Controller Hub, cooled by just a small aluminum heatsink with thermal tape on the bottom. Two inches away from that is the CPU, with memory slots nearby on the side.

That’s a lot of space heaters in a small amount of space. In my particular case, at least the CPU is being cooled by water, but you get the idea.

Prime 95

Last night, I put the board together and installed XP fresh without incident. As soon as I had my usual working setup ready, I started exploring the CPU’s limits with the now-dreaded Prime95.

Like many others, I found that the C1 cranked up into 2.9GHz-ish range without even a voltage increase. Getting it to open Windows at 3GHz needed a little extra voltage, but hardly worth mentioning.

Getting it to run at Prime at 3GHz+ was a different story, though. For instance, at 3.04GHz, Prime95 would crash within five minutes no matter what (reasonable) voltage was tossed at it.

Memory speed and timings were set way back, so that wasn’t the problem. Water temperatures felt (see below) only slightly warm to the touch, so CPU temperature wasn’t the problem.

However, something else happened, too. System board temperatures skyrocketed. Temperatures would reach about 46C doing absolutely nothing. Go into Prime time; and I recorded temperatures as high as 57C. Prime would do fine until temperatures reached into the mid-fifties. Then it would die, and not subtly, either. Can you say spontaneous reboot?

It doesn’t help that the temperature sensors are out of whack on this board (CPU temperatures are at least 20C too low), but my finger is calibrated well enough to find out that the memory hub, the back of the 9700 and everything else inbetween (including the sensor) were getting awfully hot.

The Radeon 9700 is quite capable of warming things up all by itself, both front and back. This made the air around the little memory hub heatsink pretty warm, which didn’t make its job any easier.

I thought all that heat couldn’t possibly be helping matters.

What I Did

This computer isn’t in a case; it’s on a wooden stand (ugly but very handy). Since the CPU is water-cooled and the rest of the computer is in a cool room, there were no fans cooling the rest of the computer. Up to now, there’s been no need for it.

To see if some extra cooling would help matters, I wedged a CPU fan (ironically from an AMD processor) between the CPU bracket and the memory hub so that it would blow cool air on both the memory hub and the back of the Radeon (more to keep the Radeon heat away from the memory hub than anything else).

This made the system board sensor very happy. Rather than getting temperatures like 55C, the maximum temperatures dropped to 40C.

More importantly, Prime 95 now ran when it wouldn’t before. I can’t say I’ve run it for three straight days or anything like that at 3GHz+, but I couldn’t run Prime for any length of time before, and I can now.

This isn’t a stellar CPU. It doesn’t want to hear anything about running at 3.33GHz, but it looks like it will do a little more if I keep its neighbors from getting the hots.

What You Should Do

If you’re stuck at a little below 3GHz, or just think you can get a little more from your PIV, you ought to see if additional cooling to the memory hub/video card area helps you. You really should do this if you have an especially hot video card like the Radeon 9700.

See how hot the area inbetween the CPU and video card is getting. If the case sensor isn’t in the right spot, gingerly put your finger in the area. If it feels more than slightly warm to the touch, start thinking.

There’s lots of ways you can go about doing this, so do what’s most appropriate for your setup and experiment a bit to see what works best. I just haven’t had the time to look into all the possibilities yet. Don’t be shy; tell me
if it helps or not.

This may not help everyone, or even most people. I doubt it will get anybody hundreds of extra MHz.

But if what I’m seeing is any indication, it might get you a hundred MHz, and maybe give you a little more freedom to get some improvement from a little extra voltage.

A lot of people have said that 160MHz or so seems to be a wall for many 845PE motherboards. This may be a reason why for at least some people.

All I know is that it didn’t work before, and it does now.

Email Ed

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