The 110 million transistor ATI Radeon X700 core (aka R410) is built on TSMC's 0.11 micron manufacturing technology and is closely based on the high-end Radeon X800 core. To ensure that the X700 does not compete with the more profitable X800 GPU, ATi has cut down the core to just eight pixel rendering pipelines (as opposed to 12 for the X800 Pro, 16 on the X800 XT\PE). ATi also reduced the memory controller size from 256bit to 128bit. T he otherwise hobbled Radeon X700 Pro still has the same six vertex pipelines, which means at the same clock speeds the X700 can, in theory, pump out as many triangles as its high-end brothers.

There are three members of the Radeon X700 family; the upper market X700 XT which runs with a core speed of 475 MHz and a memory speed of 1.05 GHz, but only comes equipped with 128MB of memory. Then there is the X700 Pro (used on this card) has the core running at 420 MHz, memory at 864 MHz, and comes with 256MB of memory. Finally, the budget X700 has a core speed of 420 MHz and 700 MHz memory and comes with 128MB of memory.

Heatpipe technology and the passive heatsink

ATi has stated that the Radeon X700 GPU can be cooled passively given a large enough heatsink. It seems that right now most videocard manufacturers haven't bothered trying to engineer a cooler that would work, but Gigabyte was able to do it. Up until now, the only other such option was the passive videocard heatsinks by companies like Zalman.

The GV-RX70P256V is one of the few mainstream-performance videocards on the market to be passively cooled, thanks to heatpipe technology. Gigabyte calls its thermal solution 'SilentPipe' Technology but before we look closely at the cooler on this videocard, let's talk a bit about heatpipes in general.

A heatpipe is sealed metal tube which absorbs heat from one side (the source) and moves it to another location in an effort to cool off the source. The thermal transfer is achieved thanks to a working fluid (usually water) that is vacuum sealed inside the copper tube.

With a lower atmospheric pressure inside the copper tube, the working fluid will become vapour at a much lower temperature if one side of the copper tube is heated. This is plain old physics at work - the lower the air pressure, the lower the temperature needed to boil water. When one end of the copper heatpipe starts warming up by the heat of the X700 Pro GPU, the working fluid inside the heatpipe will absorb that heat and convert to vapour. As the working fluid changes phases, it absorbs the latent heat energy carries it with it towards the cooler end of the heatpipe. Once the the vapour reaches the cooler side, it releases its heat energy into the copper tube, and consequently condenses back into liquid form. The cooler end of the heatpipe is connected to a standard heatsink, which then transfers the heat it has absorbed from the heatpipe into the surrounding environment (air). The newly condensed working fluid is then drawn by capillary action through an internal wick structure inside of the heatpipe back towards the hot end, and the entire process repeats itself.

This system seems to work extremely well with the Gigabyte GV-RX70P256V. The heatsink on the rear of the card was often as hot as the heatsink on the front where the VPU is. The heatpipe on the videocard does not come in direct contact with the core; instead there's a small copper heatspreader between the core and it.

The red and gold aluminum heatsinks on the back of the card are actually a two piece solution. The red aluminum heatsink is specifically dedicated to cooling the heatpipe, while the gold aluminum heatsink is used to cool the back of the VPU, through the PCB itself. Between the chip and the heatsink is a thick white thermal transfer pad. Gigabyte's SilentPipe Technology does an excellent job at cooling the videocard, and during testing we did not experience any stability problems related to heat.

Overclocking the X700 Pro!

We've had some luck overclocking ATi cards in the last little while, and I was hoping that this would continue with the Gigabyte GV-RX70P256V. I immediately raised the core clock speed (420MHz by default) to X700 "XT" level (475MHz), and the card had no problem running at this speed. I then tried for 500 MHz, but unfortunately the GV-RX70P256V locked up immediately under these settings.

Returning to 475 MHz, we started increasing the core speed slowly. In the end, the card was able to hit a maximum core clock speed of 491 MHz. Not bad considering that we started from 420 MHz. With some form of additional active cooling the core could probably overclock a little further, since the heatsink temperature was well above 50 degrees Celsius during these tests.

Since the Gigabyte GV-RX70P256V uses Samsung K4J55323QF-GC20 DRAM, I was hoping the memory would be able to hit 1 GHz. Starting at the default 864 MHz, I increased the speed a few MHz at a time. Unfortunately, while it was able to pass the 900 MHz mark, t he maximum the memory would do was 904 MHz. Anything higher and the videocard would lock up the system when running 3DMark05. I was slightly disappointed by the results here.