8600GT Voltmods

First Look

The 8600GT and 8600GTS seem to be very close in specifications, the biggest difference lie in the clockspeeds. We've seen that the 8600GTS is a high clock speed Demon... how high then does the 8600GT go? Can a 8600GT clock up to 8600GTS speeds without any mods and hassle? We take an initial look at the overclocking capability of the Inno3D 8600GT and Palit 8600GT.

Inno3D 8600GT

Palit 8600GT

The Inno3D 8600GT uses a single slot small black aluminum ORB cooler.

Palit uses a more hefty solution: Zalman Cooler that chalks up 2 slot spacing.

Default Clocks

Qimonda 1.4ns Memory on the Inno3D, while the Palit houses a heatsink over the RAM chips. Upon removing the RAM sinks, I saw that the Palit spots slightly better Memory, Qimonda 1.3ns:

No need for a PCI-E Power connector on the Inno3D, nor for the Palit - one of the key difference between a GTS model and a GT model.

Back of Inno3D

Back of Palit

The Inno3D 8600GT comes clocked at 540MHz Core and 700MHz Memory, and the idle temperature of the core stays at 46C.

On the other hand, the Palit 8600GT is clocked at 600MHz Core (11% higher than Inno3D), and 800MHz Memory (14% higher than the Inno3D). It idles at a lower temperature of 41C, probably because of the better Zalman cooler on the card.

Overclocking Tests

Platform Test Setup
CPU	Intel Core 2 Duo E4300 Overclocked @ 9 x 266MHz = 2.4GHz
Motherboard	ASUS P5N-E SLI 650i SLI
Memory	2 x 1GB GSkill F2-8000PHU2-2GBHZ DDR II set to run @ CL4-4-4-12, DDR2 800MHz, 2T
Graphics Card	Inno3D 8600GT 540/700	Palit 8600GT 600/800
Hard Disk Drive	Seagate 80GB Barracuda SATA Hard Disk Drive
PSU	SilverStone Zeus ST56ZF
Operating System	Windows XP Pro

*Drivers Used is Forceware 158.19*

3D Mark 06 Default Performance

3D Mark 06 default performance shows that the Palit is faster by 9% due to the higher factory clockspeeds.

However, the most important thing for me was to find out when overclocked, how far each card is able to go? Does Higher Factory Speed means a higher limit?

Venturing to overclock the cards without doing any modifications:

Inno3D 8600GT

The Inno3D 8600GT goes to a speed of 692MHz Core (28% over default), 925MHz Memory (32% over default). You can say that there is a 30% headroom for you to play with, without any hassle. 3D Mark showed a 24% boost in performance.

Palit 8600GT

The Palit 8600GT goes to a speed of 723MHz Core (22% over default), 950MHz Memory (19% over default). You can say that there is a 20% headroom for you to play with, without any hassle. That is 10% lesser headroom than the Inno3D since it came much higher clocked. 3D Mark showed a 17% boost in performance.

Eventually, when we overclock them, the Palit ends up 3% faster than the Inno3D, as compared to the 9% before we overclock them. At the end, I found that this was due to higher default voltages running on the card. For Inno3D, the default Core voltage is 1.33v, while the Palit runs it at 1.4v, 0.07v higher. While the Memory voltage of the Inno3D runs at 2.0v, the Palit runs it at 2.1v. Aha!

Also, you see that a 8600GT when overclocked, easily comes up to or supercede the default performance of a 8600GTS.

Inno3D: Voltage Mods & OC

Let's try some voltage mods. Easy as hell, just a pencil will do it for both Core and Memory voltages! The two cards are modded differently as they are built different. I first played with the Inno3D. Here are the voltage mods for the card.

*Take Note that all physical Modifications Void your warranty!*

You can measure GPU voltage and Memory voltage from the points marked above, with the help of your multimeter. Pencil the resistor above to increase the GPU Core voltage, form the default of 1.33v. Alternatively, you can solder on a 20K ohms Variable resistor to point shown, with other leg connected to ground. Set at Max 20K ohms, Decrease resistance to increase voltage.

For Memory voltage, pencil the resistor above to increase the GPU Memory voltage, form the default of 2.0v. Alternatively, solder a 20K ohms Variable resistor to point shown, with other leg connected to ground. Set at Max 20K ohms, Decrease resistance to increase voltage.

I improved cooling on the card...

Upon removing the heatsink fan on the Inno3D card, I found the interface to be the common pink thermal pad one typically finds between a Motherboard's chipset and cooler.

As I tuned Core voltage to 1.7v and Memory voltage to 2.25v, I switched out the small cooler for a Brutos-the-Barber Beefcake Cooler.

And yes, 921MHz Core and 952MHz Memory is reached with just air-cooling, and the help of a pencil - 1.7v Core, 2.25v Memory. That's a 70% overclock on the Core, and a 36% overclock on the Memory! 3D performance goes up by a huge 44%!

I'm done with the Inno3D 8600GT in terms of overclocking for now, while I try my hand on modding the Palit next. Impressive headroom on the overclocking, lags behind the 8600GTS I've tried, but not by too much. With some skills, one can take it over 900MHz Core! Next page shows the Palit...

Palit: Voltage Mods & OC

Below shows the simple pencil mods to raise voltages for the Palit 8600GT:

*Take Note that all physical Modifications Void your warranty!*

You can measure GPU voltage and Memory voltage from the points marked above, with the help of your multimeter. Pencil the resistor above to increase the GPU Core voltage, form the default of 1.4v. Alternatively, you can solder on a 20K ohms Variable resistor to point shown, with other leg connected to ground. Set at Max 20K ohms, Decrease resistance to increase voltage. Same thing with Memory voltage, can be done with a pencil or variable resistor, shown above.

I tried overclocking with a bump in voltages without changing out the Zalman Cooler first.

With 1.5v Core and 2.25v Memory, 800MHz Core and 950MHz Memory!

The real surprise was to switch out the Zalman cooler with my trusty ten-buckaroo Copper-chunk. This was to provide room for the high voltage I was about to pump in. This card scales very responsively with the rise in GPU Core voltage!

I death-defyingly dripped 1.75v into the Core and retained Memory voltage at 2.25v.

The result was quite stunning, surpassing my overclock on the 8600GTS I tried. Well over 1GHz Core, 1020MHz on the Core was achieved. The Memory bandwidth was pulling it back as there was no way to hit 1GHz Memory with the 1.3ns RAMs. 1020MHz Core and 955MHz Memory and it was just so close to breaking 7K on 3D Mark 06!

The Palit 8600GT proved to be a formidable overclocker, yielding results better than the Inno3D 8600GT, hitting an even higher clockspeed that my 8600GTS gave. The G84 core from the same vine once again showed that 1GHz core with aircooling is so achievable, even on the lower-end 8600GT. This is even more of a pleasant surprise when one is reminded that this card spots no PCIE power connector, drawing it's whole power through the slot. The only disadvantage this 8600GT spots compared to a GTS is the slower Memory on the card, which is why it can't reach the same height as a GTS, albeit it comes sniffingly close!