Checking the Heat & Pulling the Bars

NVIDIA's G92 now puts the successful G80 architecture on the 65nm process. After the 8800GT's release, NVIDIA rolled out the 8800GTS 512MB to realise the full rendering potential of 128 Shader Processors. NVIDIA's well-executed die-shrink has been causing a stir in the overclocking community. Out of the box, the 8800GTS 512MB easily reaches clockspeeds that trounces a fair few highend graphics accelerators. A bit of work is all it takes to squeeze extra performance out of your purchase so you can be cruising through Crysis with a few more options enabled. The star of today's show is XFX 8800GTS Alpha Dog Edition which comes factory overclocked at 675/1674/990 (we'd be using this format of presentation for clockspeeds throughout this review). This thing does a fine 14823 in 3DMark06, when it's slower brethren would only do 14456 out of the box.

Generic 8800GTS in 3DMark06.

The Alpha Dog munching down Futuremark.

Of course, most of our readers here don't stop at overclocked graphics accelerators. They go on to overclock overclocked graphics accelerators. This is exactly what's on the menu today; we take the XFX 8800GTS XXX Alpha Dog edition for a ride down the clockspeed highway. Most factory-overclocked graphics cards are notorious for poor overclocking headroom due to the already-high clockspeeds programmed into them. Whether or not the Alpha Dog will justify it's price tag for the LN2-hugging overclockers' everyday PC shall be explored in this review. Before the nitty-gritty, let's just undress the Dog.

If there was an anti-static G-String equivalent, this is it.

Now that we're done with looking at the overall package, the first thing an overclocker has to do is to get your hands on a graphics accelerator overclocking utility. RivaTuner has been gracing our labs for a fairly long time, and that is what we need today. In it's 2.06 revision, you won't get to recognise the G92 8800GTS 512MB immediately after installation. What you need to do is really simple. Grab this configuration file and throw it into your RivaTuner installation folder in replacement of the original. Mission complete? Move on soldier!

2.06 does not immediately recognise the 8800GTS 512MB.

Eventually, you can make it work.

Next portion is pretty cool, you get to gain the status of a "Power User" which comes close to sounding as Marvel as the Man-in-Rayon. Tab over to "Power User" and check the option, clicking "OK". Now you should see an array of options. Expand "RivaTuner \ NVIDIA \ Overclocking" and replace the blanks with "1" as follows. This keeps your eventual overclocked settings in shape.

Scroll to the "Rivatuner \ Overclocking \ Gobal" part and expand the list. Put a "1" in "DisableClockTest" so you don't have to get a message bugging you to be The Great Stock-Clock Saint. Under "MaxClockLimit", throw a large value in the box so you never get to hit the end of the bar.

Now go over to "System Settings" in the RivaTuner panel. Check "Enable driver-level hardware overclocking." Out pops an option box. Keep "Allow Separate 2D/3D Clocking" checked. Uncheck "Link Clocks" You're ready to start pulling the bars! For convenience, launch a 3D application in a window so you can load the graphics accelerator while you overclock on-the-fly. Games running in Window mode, or RTHDRIBL works well here. ForceWare 169.21, Windows XP Professional 32bit, Asus Maximus Extreme with PCIe frequency raised to 120MHz, Enermax Galaxy 1kW PSU and Cosair Dominator RAM are on the menu for today. Credits goes to Firefox and floppy for configuring the tweaked-out test bed.

Penryn power.

The 8800GTS uses a dual slot thermal solution known as the TM68. As we've discovered, the heatsink element has no fewer than 3 heatpipes. Very hefty for a default cooler even by today's standards, and definitely no slouch when you pump up the fan speed. If you're out of budget for better cooling, you're not out of luck overclocking the 8800GTS. To take care of the heat, launch RivaTuner and drag up the fan speed. Under control, select "direct control" and check the box allowing this setting to be applied on boot.

Whining for the eyecandy.

After some trial-and-error, our Alpha Dog came to 799/1998/1080 on core/shader/memory clocks. That's a FREE 13% boost in 3DMark06 scores!

Extra Cooling

Cooling is paramount to making transistors switch faster. When a well designed GPU thermal solution is just not enough, we turn to CPU coolers for a little more kick-in-the-posterior. We dug out a battered Noctua NH-U12 and put it on the 8800GTS with the help of Thermalright HR03's supplied mounting bracket. For the purpose of today's article, let us just blame the craziness on the paint vapours inhaled at our newly renovated test labs. =P

Nice and cosy with a Nidec TA450DC 9.6W.

The extra cooling put the core temperatures under 40 degrees Celsius during load, and allowed us to scaled another notch up on core speeds, giving an eventual 810/2052/1080. Shader clocks have to rise in tandem with core clocks to scale upwards. Thankfully, RivaTuner allows unlinked clocking of the core and shader components. Notable is the poor granularity between clock jumps, which can be verified by opening the Monitoring window.

With extra clocks available, 3DMark06 went a wee bit higher. What cooling alone does is limited, hence we show you new tricks on the next page.

Voltage Modifications & Extra Works

The G92 chipset has been running the 3DMark threadmill for hours on end. It's cold under the Noctua, and hungry too. We can feed it some juice by doing some voltage modifications to the 8800GTS. It took us a while to figure the works and eventually realised that some of the guides have already been scattered over the Net. The modification points for most purposes are identical to the 8800GT, so we won't take any credit for it.

Map to Clockers' Cove.

Measure points.

We figured that we could just dump you a picture and leave you in the lurch, but here's a few points to take note as we explain the modifications. The top-left dot is the feedback sense pin of the PX3544. The less voltage it detects, the more it causes the regulation system to pump out. The feedback pin on the ISL6459 is pin 4, shown in this diagram as the bottom-right dot. You need to find linear (B type) multiturn variable resistors for better control over voltages. Bourns, Nidec (Copal) and Spectrol makes them, amongst others. They are stocked by major retailers electronic supplies mail order chains like RS, Farnell, Allied, Digikey, Arrow and Tandy. Singaporeans can pop over to this thread for some shopping tips. To castrate the overcurrent protection, get rid of the three resistors marked with "78X" on them. This optional modification may however allow extra stresses on the VRM system.

Default Vgpu is around 1.17V, while default Vmem lies at about 2.02V. We gave the core a nice 1.22V and tested a few different memory voltages before settling at 2.07V. This gave us 837/2106/1098 in clocks. 3DMark06 registered 17199. Looking at Deep Freeze framerates, that's roughly 22% faster than any run-of-the-mill 8800GTS.

The Final Numbers

Additional Firepower

We crossed our fingers for an all-out test on forced-air cooling. An additional capacitor was placed across the Vmem rails so those little Qimondas get a good deal more clean fun. The Vgpu rail had one too. Sanyo's 6.3V, 1500uF WG fitted the bill for it's low ESR and small size.

I admit, it's not that small after all.

A few extra MHz were squeezed out of the whole setup, while a streamlined Windows XP Professional installation with Forceware 169.21 drivers took over our earlier Vista setup. We prodded the FSB a bit and tweaked out the mipmaps.

And we end off the day with...19643 3DMarks!

1.5V Vgpu, 2.11V Vmem.

Time for some 2560 X 1600 Unreal action! Good luck clocking guys! ;)