HD3870 Crossfire, spacing and cooling.

morelenmir · 6 Jan 2008 at 14:29

Hey Forum!!!

I have been struggling with the cooling on my HIS HD3870 Crossfire machine.

When both cards are plugged into 16x PCIE slots on my Maximus Extreme motherboard there is practically no clearence between them. This leads to the top card being pretty starved of air. Accordingly when I first put my machine together the stock cooler did a pretty terrible job - 74 degrees at idle! Since then I replaced the coolers with two DuOrbs. This made a HUGE difference and the cards now idle at ~40 and ~30 degrees respectively.

However, when running Stalker - the most graphically intensive game I have - the top card heats to around 65 degrees. Frustratingly the lower card which has no shortage of air goes no higher than 40 degrees at the most. I am pretty sure if I could space the cards better they would both heat to around the same temp.

Given all this I have a couple of questions to pick the brains of the board!

Firstly, is 65 degrees under pretty much maximum load anything to worry about? As I said the card used to IDLE higher than this, but I still feel it is not ideal.

Secondly, the real reason my top card is so hot is because its fans are stifled by the base of the bottom card. Usefully the ME motherboard does have a third, lower 16x PCIE slot. If I could move the bottom card here I am sure the top card's temp would improve. To do so however I would need much longer Crossfire bridges than those which HIS provide - perhaps twice as long. Is it possible to get hold of such things?

Any advice on this issue gratefully received!!!

Richie P · 6 Jan 2008 at 17:39

1st, 65C under load is nothing to worry about - i'm actually impressed at how good a job those DuoOrbs are doing with the 3870's

GFX cards have a much higher temp limit that CPu's, and are usually ok up to 100C ish. Keeping it down at 65C will be very good for the cards and you should think about overclocking

Also, I might have an explanation for the temp difference.

Think of Crossfire like a dual core CPU - when you run a single threaded app, it only loads one of the cores which heats up and the second remains cooler. If Crossfire isn't scaling too well, that second 3870 might not be getting much use.

Try 3dmark06 which should load up both GPU's as much as you can - see what the temps are like during a run of that

Blackout · 6 Jan 2008 at 18:35

Welcome to the forums morelenmir

morelenmir · 6 Jan 2008 at 20:31

Hey guys! Thanks for the replies and warm welcome!

I'll let 3dmark give my cards a good work-out and see how the temperatures stack up.

In some ways if the higher temps are not to worry over I am a little sorry I switched to the DuOrbs. They certainly do a tremendous job, but are considerably more noisy than the nearly silent stock coolers. Still - better to go with a slightly more noisy solution I guess which buys thermal headroom for a touch of the overclocking as suggested!

Cupra · 6 Jan 2008 at 20:51

i have a peice of plastic pushed between mine and some fans facing to cool the top card down, lowed to aroun 7 deg of the bottom card now

morelenmir · 6 Jan 2008 at 22:23

My mind was ticking along those lines also Cupra! Maybe a big, slow 120mm fan would get a bit more air down to the DuOrb. I can't quite see from the photo, are you using the stock coolers or an aftermarket piece? What temps are you getting with your rig?

It is interesting you mention putting a plastic spacer between the cards. I have also - although possibly for a different reason. In my case, I found the mounting nuts of the DuOrb so unnecessarily long that those from the lower card actually jutted into the fan blades of the upper! They only just touched, but with the weight of the sink and card pulling down it made an aweful chain-saw rattle until I 'installed' a spacer to keep them apart.

marscay · 7 Jan 2008 at 00:15

i did the same thing for mine with the stock coolers, the outside memory heatsink was roasting @ 1260 on both cards so i figure a yate loon can't hurt and doesn't make any noise.

i run my fan @ 50% on both cards and get about 60-65c load on each, neither get hotter than the other.

morelenmir · 8 Jan 2008 at 11:35

Those figures are VERY impressive from my experience with the stock coolers marsay. The original fans on my cards were almost silent, certainly in comparison to the DuOrbs - but I think the low noise was defiitely paid for in temp.

marscay · 9 Jan 2008 at 22:02

i've just flashed my 2 cards to a bios which has the pll unlocker and also proper fan control.

it now dynamically changes to keep temps ~60c under load and works very nicely, in idle it sounds like it's at 35% and keeps both cards ~40c - both cards @ 865/1261.

for me personally aftermarket cooling for these cards isn't needed unless you want silence, especially if you have 2 cards and therefore 2 coolers 50-60quid??? no thanks!!!

this new bios sounds very respectable under load now and keeps temps at a nice place with a decent overclock.

GothicGhost · 10 Jan 2008 at 03:22

sry to be off topic but cupra where have you put your harddrive? lol

Big.Wayne · 10 Jan 2008 at 04:07

Cupra said:

Cupra do you think you could fit anymore fans in there to help cooling?

Is 13 enough!

Cupra · 10 Jan 2008 at 05:02

Big.Wayne said:
Cupra do you think you could fit anymore fans in there to help cooling?

Is 13 enough!

there is another pa 120.2 with 4 on u cant see, plus 4 92mm fans cooling my hdd,s blow the psu (behind the mobo tray) there is also the psu fan itself
ill start from the front

5x orange bladed thermaltake fans (came with the case)
1x 92mm antec fan
1x 80mm fan blowing along gpu's
1x 92mm antec fan blowing @ watercooled nb (and the pll voltage regulator)
1x mosfet cooling fan that asus supply with the mobo
2x 120mm fans blowing direct at the gpu's fromnt he sides
2x fans on the gpu's
4x 92mm antec fans cooling hdd's
1x 140mm fan on psu
8x 120mm fans cooling rads
1x 92mm fan that fell over that was blowing air out the case below the psu

but without all that matey how would i get this?

http://valid.x86-secret.com/show_oc.php?id=294007

imo its worth it

when im not benching i have case and rad fans only tbh, but they genuinly do help me get the little extra air moving about my case

w3bbo · 10 Jan 2008 at 09:00

R.I.P

roadie · 10 Jan 2008 at 11:40

marscay said:
i've just flashed my 2 cards to a bios which has the pll unlocker and also proper fan control.

it now dynamically changes to keep temps ~60c under load and works very nicely, in idle it sounds like it's at 35% and keeps both cards ~40c - both cards @ 865/1261.

for me personally aftermarket cooling for these cards isn't needed unless you want silence, especially if you have 2 cards and therefore 2 coolers 50-60quid??? no thanks!!!

this new bios sounds very respectable under load now and keeps temps at a nice place with a decent overclock.

Link please!

I flashed my card's BIOS to one that gave stock speeds of 830/1200Mhz and supposedly improved the responsiveness of the fan controller to temperature but it didn't make much difference to temps. I still have force the fan speed to 70% using Rivatuner when gaming and would like to skip this step if possible!

marscay · 11 Jan 2008 at 04:50

roadie said:
Link please!

I flashed my card's BIOS to one that gave stock speeds of 830/1200Mhz and supposedly improved the responsiveness of the fan controller to temperature but it didn't make much difference to temps. I still have force the fan speed to 70% using Rivatuner when gaming and would like to skip this step if possible!

here you go m8, this one is what you're looking for.

i flashed in dos with latest atiflash so i'd recommend you do the same and not use the winflasher as i can verify the dos one works fine.

http://www3.sympatico.ca/ocd/bios/3870fanfix.bin