While industry watchers may comment that the discrete graphics acceleration market is far from saturated, two strongholds are all it takes for an almighty pixel warfare to break out. The need for a single-card, motherboard chipset independent graphics acceleration product becomes apparent. Previously, Asus, Galaxy and Sapphire have pushed out products utilising two GPUs on a single expansion card, yet these unacknowledged products were merely the technological equivalent of a warhead parade - taunts that instilled fear in enemies and drew new allies.

This creates the niche for multi-GPU (read: dual-GPU) solutions which don't require hardware upgrades other than the graphics accelerator itself. Before the GeForce 9800GX2 hits the market (or NDA for that matter), AMD has already sneaked it's 3870X2 into stores around the globe.

With us today, is the PowerColor 3870x2, a default ATi design. We also have a couple of shots of the Asus 3870X2, an Asus engineered rendition with not two, but 4 DVI outputs.

Asus's HD3870 X2 isn't quite the norm, with a quartet of display outputs. It shares much of the BBA components, and performs similarly.

PowerColor's HD3870 X2 belongs to the family of "reference" designs that stick to the same circuit board and thermals as suggested by ATi. More likely than not, most HD3870 X2 cards would be similar to this.

Behind every successful overclocker is a well managed thermal solution. The original HD3870 X2 would be a tough nut to crack on cooling at the moment, so ATi had better done some good work on it.

Mounting holes are 59mm apart diagonally. Thermal pads form the interface for larger semiconductors, and a 12W blower draws air through the skived heatsinks. The module nearer to the fan (presumably the cooler one) is an aluminium unit by default, while the module nearer the exhaust is copper. Conduction does not involve heatpipes.

For an axial blower, the default thermals ran surprisingly silent with fan control at hand. However, load temperatures ran into the eighties. To improve things, we need fan control. RivaTuner works well for that purpose.

Or so we thought. The existing installation of RivaTuner (2.06) has yet to support RV680, so we did a little trick to enable fan control in the nifty program. First you have to download this file and head over here to the RivaTuner installation folder.

Drop the file in and replace the original configuration file. Now when you launch RivaTuner, it should be able to recognise the HD3870 X2.

Tab over to "Fan" and set the fanspeed to your liking. We blasted it up to 100% because we wanted maximum cooling. That alone isn't quite enough.

We cut apart some zip ties and slot them under the original "X" bracket for holding the heatsink modules.

Temperatures shown are those before and after the mounting pressure modification. Load temperatures fell with both the additional fan speed, and mounting pressure.

Overclocking introduces instability, and overclockers have to tradeoff between speed and "benchmarkability." Instability for benchmarkers often show up as artifacts, or the inability to complete tests.

We raised PCIe frequency to reduce possible texture-transfer bottlenecks. LinkBoost for ATi? Maybe.

Overclocking the HD3870 X2 beyond OverDrive capabilities invloves the use of a more capable overclocking tool. All you need is to download this utility, unzip it, and launch the executable. Linked clocks are however not functional, and you need to apply clocks for it to work.

A little trial and error gave us 22K in 3DMark06 on Quality mipmaps. Driver was a beta of the 8.45.1.2 version. More on the system below:

To raise switching frequencies of chipsets, cooling the semiconductor device is only part of the equation. By raising operating voltage, transistors withstand faster switching during overclocking.

These are the device IDs for each core so you know which "core" you're adjusting when you run the Vgpu modifications.

Switching over to Windows XP and Performance mipmaps, we ended up with 918MHz/1134MHz on the GPU/MEM clocks. This was acheived with 1.49V on BN:4 and 1.43V on BN:3 (all voltages measured in 3D mode). Memory voltage was untouched. GPU quality differs across the board, so expect to treat them like individuals graphics accelerators when voltage tweaking.

Most of the modifications have already been figured by Shamino over here. While overclocking, we realised that raising memory voltages allowed higher clockspeeds to be attained in benchmarks, yet stability did not improve, and we continued to see artifacts even after scaling voltages. We have with us a little more trick to try.

By performing the above modification, you can adjust the reference termination voltage for the memory modules. We were not able to remove artifacts resulting from a graphics buffer overclock, but it brought about less visible "swarms" seen during GT3: Canyon Flight. We recommend you look up Vref recommendations on the datasheet of the memory affixed to your HD3870 X2 prior to attempting the modification.

As with all the other modifications within the article, set the potentiometer to the highest resistance before powering up and adjusting voltage. Not enough extra components on the board? Here's some more!

Ruby1 and Ruby2 didn't mind some "caps" on, but they are neither of French nor Dutch origins. The Japanese capacitors used here are Sanyo WG low ESR, 1500uF, 6.3V ones.

Just for a little benching pleasure we ramped up whatever little headroom was left to play some numbers. Stability was secondary, as most would have guessed. BN:4 refused to move despite voltage scaling, so we kept to synchronous clocking. Memory speed went up a notch with modifications in place.

With 2.27V on memory, 1.59V on Vref, 1.55V on BN:4 and 1.49V on BN:3, 22.7K score in 3DMark06 was taken. The only let down was the poor matching of the GPU cores (one could perform at 1012MHz with a slight voltage bump).

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