ATI Radeon HD3870 X2 1GB Review

Under the Heatsink


Once the heatsink is removed we are greeted with the two RV670XT cores as well as the large bridge chip. From what I see, adding any existing aftermarket cooler to this card will be a lesson in futility though it should be interesting to see what kind off crazy coolers come out in the future for it. Yet, we like challenges here at Hardware Canucks so a bit later in this review I will be discussing the possible aftermarket heatsink and water block ptions for this card. Since this is an engineering sample there are a few oddities as well such as mismatched copper and aluminum heatsink bases.

The back of the card holds the additional GDDR3 memory modules which combine with the front ones to create an 8x 64MB layout of memory around each core.


The ram modules used here are Samsung K4J52324QE-BJ1A modules which are rated to run a 2Ghz (DDR) at 1.9V so this should give a bit of overclocking headroom since they are running at 1800Mhz on this card. The full spec sheet can be found here: http://www.samsung.com/global/system...24qe_rev12.pdf

Between the two cores there are additional traces and resistors for the bridge chip we will take a look at in a moment.


Here is the real star of the show: the PLX Technology PEX8547 PCI-E switch. This chip handles the communication between the two GPUs which eliminates the need for a Crossfire bridge. The die is actually quite large at 38mm X 38mm but it only consumes a maximum of 4.9W so it should not produce much heat at all. While I could talk on and on about this chip, I will instead direct you to the product brief:
http://www.plxtech.com/pdf/product_b....5_15Aug07.pdf

It makes for some interesting reading and I suggest you go over it when you have a few minutes.


On this engineering sample, there is a trio of large Pulse voltage regulation modules which are placed at various parts of the card. Since these tend to build up quite a bit of heat, they are interfaced with the heatsink base with thermal pads. You may notice that there are additional solder points for another of these modules next to the one at the rear of the card but it looks like ATI figured they only needed one at this location.


Both cores are identical to the ones we saw a while ago on the HD3870 512MB. They are 55nm RV670XT cores which are attached without an overly-large IHS since they produce very little heat compared to the space-heater 80nm cores of yesteryear.


It really is stunning to see the amount of engineering that went into this card and let’s hope that all that hard work will equal acceptable performance.