EVGA 8400GS Volt Modification and Overclocking
01.31.08 - 05:56pm
Title says it all. I decided to pull out the meek 8400GS for a little fun along while competing in a little competitive event over at XtremeSystems. I originally purchased this card for when I’m benching to reduce the load on my powersupply in hopes of pulling a few more MHz out of the processor. I however just couldn’t resist overclocking this card so in the original review I managed to pull 600MHz out of the core and 415MHz out of the memory. Considering the stock clocks of 459MHz on the core and 400MHz on the memory, it overclocked moderately well for a $30 card.
Just Add Cooling
Just to make sure I didn’t run into any thermal walls I decided to swap out the original heatsink for something a little more beefy. When overclocking on the original heatsink the core was hitting 60C so I knew there was still plenty of headroom available but this time around I was going to actually manipulate the voltages also. Looking around the room, I saw three options. One, find a way to strap the cascade to the card. Two, butcher an Intel stock heatsink to fit on the card. Three, modify a Thermaltake Big Typhoon. The first option would have resulted in some massive core overclocks but considering how I didn’t know how much voltage I’d need, the cascade was out. That left me with the Big Typhoon or the original heatsink. Considering how each heatsink would require about equal amounts of work, so I opted for the Big Typhoon. This is in no way a permanent solution, but here’s how I mounted it.
Voltage Modification
When operating switching circuits there are a few things you can adjust to increase it’s ability to run faster. With memory you can re-adjust timings, with processors you can manipulate I/O and multipliers, but universal variables include temperature and voltage. The hotter a chip is running the lower it’ll clock, this can be scene with processors where 1.5v on air will result in 4GHz while 1.5v under -80C results in 4.8GHz stable. At the same time, increasing cooling will only net you so much so therefore a voltage increase is required. Voltage itself can typically vary within a comfort zone and be safe but when you start hitting high(+50%) voltages you greatly increase the risk of damaging the very circuits you are trying to tweak. The modifications below have been tested on an EVGA 8400GS and work just fine, use them at your own risk. Just a note, I didn’t create this image, I found it after I had mapped out the vGPU mod, but I used the image to map out the vMEM mod for confirmation. I don’t remember where I grabbed the image, but props to whoever snapped it.
Results
This G86 core scaled incredibly well with voltage but the memory offered terrible performance. I would kill for some GDDR3 on this card as it’s drastically memory limited. When benching, a 10MHz increase in memory was equivalent to a 100MHz on the GPU, a huge sign of memory limitations. I decided to stop at 1.75vGPU as I feel I need to beef up the onboard PWM a bit with some extra capacitors and chokes. I think going sub-zero will also yield some additional GPU clocks but I think the memory is stuck at ~840MHz unless I can tweak the BIOS for looser memory timings. This is just the begining for this clock, in a week or so I’m aiming for 1GHz on the core with the beefed up PWM and tweaked BIOS. Oh, for those interested the 3DMark performance still blows, 22,098 points in 3D2001 with the processor at 4GHz.
Nice job :D Ive never seen someone go so far to overclock a budget card like that :) We should put that thing under cascade or LN2 :)
Cheap benching is a lot of fun as you care so much less about the safety of the card. With my 3850’s I wouldn’t dare put 1.5v into them without some serious cooling, I have no qualms throwing 2v at this 8400GS though. Too bad the RAM clocks so horribly, it has some potential to do moderately well in 3DMark.
I got mem clock up to 460. Thats 920mhz! 150mhz faster! evga 8400gs 559 coreclock
I took and old VGA Silencer rev.3 (Arctic cooling) and was able to get the core to 626 and the mem to 475 with no voltage changes. The gpu is limited around 600 with stock voltages. The silencer should allow about 1.5v, going to have a go at it. The 3dmark05 @ 626/475 was 4400. I am going to add some memory syncs and see if I can get the mem to 1000/1100 which would really help this budget card pull some decent numbers. for $30 directx10 and 5K in 3dmark05 I have no complaints.
im curently at 561 core 1200 shader and 460 mem stck cooling
Well done! I am lack of basic skill. Where should i start to learn it?
Just need this guide.