8K3A+ Mofset cooling?

[MasterPooBaa]

Im pretty sure someone did a how-to giude on what mofsets and chips need cooling on a 8k3a+ to get better and more stable voltages. Does anyone remember the link to it?

p.s. are there mofsets on the back of the 8K3A+ to cool as well?

thanx in advance.
poohey

[Gizmo]

There is no thread about cooling the 8k3a in particular, and I didn't find anything in a quick google search.

If you will look at the pic I have attached, I have outlined in red the area where your CPU power switching FETs are located. There are three of them. If you are OCing, then you will probably want to cool these. How best to achieve that will require some experimentation on your part. A lot of people use little RAM-sinks, which are about the right size, and just epox them to the top of the FET. While this isn't a bad idea, it isn't going to make a lot of difference in the actual temp of the FET, because it isn't designed to dissipate heat that way. The FET wants to get rid of its heat through the metal tab on back, which is soldered to the the mobo. This means that the mobo is acting as the heat sink for the FET. As such, you need to try to cool that area of the mobo. What I have done in my case is I have put a fan right above the mobo such that it blows air down behind the mobo and cools the back side. It made about a 50C difference in my FET temps. 'Course, I was pushing them pretty hard to start with.

There is probably not an awful lot else on that mobo that is in dire need of cooling. You might want to take the heat sink off the north bridge and add an active cooling solution there, though. Or at least get a fan on it.

[Gizmo]

Sorry, I didn't realize quite how small that pic is. The area in the upper left corner is what I was talking about.

[nfrenay]

I don't think that heatsinks on those FETs will help with anything. It's probably more interesting just to use a FAN to blow some air on top of them.

I use a 80mm fan to blow air over these FETs and my memory, because my CPU is watercooled so there is normally no airflow to get the heat out of there.

I'm pretty satisfied with my voltage variations in comparision to other boards I've seen on other forums.

[smiffy]

Try cooling the mem buffer chip on the right side.(just above the floppy slot)It gets quite hot
Smiffy

[Woof!]

There are six fets on the 8K3A, 3 on the frontside and another 3 on the backside. This design has been abandoned by epox in favor of the six inline design for 3-phase power. The latest revisions of its current boards seem to adopt a 2-phase system (cost-cutting?).

I normally just point a big fan (120mm) on the general area of the mosfets, CPU and northbridge to cool them all simultaneously.

[Gizmo]

Originally Posted by Woof!

There are six fets on the 8K3A, 3 on the frontside and another 3 on the backside. This design has been abandoned by epox in favor of the six inline design for 3-phase power. The latest revisions of its current boards seem to adopt a 2-phase system (cost-cutting?).

Really? That's interesting. All I had to go off of was the picture. I thought it was rather odd that there were only three FETs there, but thought maybe they were using a diode on the low side instead of a second FET.

Yes, I would imagine the 2-phase system was done for cost-cutting, although according to ET it also produces much less heat.

[MasterPooBaa]

ok i got my multimeter temp probe working once more, so ive measured my moffie temps.

Turns out they are pretty good, below 40c for the black bit, hottest part was the small metal strip which connects the mofset to the mobo at ~45C.

The 2 chips around the moffsets were in the mid 30's.

And Mr smiffy was right, the mem buffer chip next to the FDD port was a considerably warmer 51C, possibly the hottest thing on my mobo.

As far as REAL cpu temps are concerned, my XP-M 2500+ @ 2333Mhz & 1.65v gives me a temp of 32C, mesured at the big copper block of the MCX-462 cooler.

not too shabby!