ATI’s Radeon HD
3870 X2 series pairs two R670 GPUs together. Each CPU is made on the 55nm
process, and the chips containing a rather ominous 666 Million transistors. By
the numbers, the
R670 feature 320 stream processors, 16 raster operation units and
16 texture units. The ASUS EAH3870 X2 PCSTATS is testing has been factory
overclocked by ASUS to an 850MHz core clock speed with a 950MHz memory clock.
That's an increase from the ATI default clock speed of 825MHz GPU. The 1GB of DDR3 memory
runs at 950Mhz (1900Mhz DDR), which is up from the stock speed of
Functionally, the twin R670 chips on the ASUS EAH3870 X2 co-operate just
as if they were on two separate videocards in two separate PCI Express slots.
This is possible due to the fact that the Crossfire logic is actually built
directly into the die of the R670 GPU.
Each R670 chip simply requires a means of transferring the
necessary synchronization data to any other compatible GPUs. The HD 3870 X2’s design provides an internal PCI-Express switch (based on the
PCI Express 1.1 standard, so capable of a maximum of 4GB/s bandwidth) which connects the
two cores and carries data in and out of the card. Each GPU has
access to a dedicated 512MB of video memory.
ATI has designed the HD 3870 X2 to use DDR3 memory, rather than the faster
DDR4 memory used in the standalone HD 3870 reference cards. Why this should be
is not really clear, as ATI's next-generation dual R770 (HD 4870 X2) design uses
DDR5 memory… Possibly the interconnects on the 3870 part necessitate slower and
more stable video memory, while the faster connections are better suited to the
On the other hand, the HD 3870 X2 sets the default clock speed of its twin
GPUs 50Mhz higher than the stock Radeon HD 3870.
Microsoft’s newest graphics API, DirectX 10.1 is fully supported
by the Radeon HD 3870 and HD 3870 X2. Also included in the HD 3870 X2’s feature
set are additional HD video display features designed to enhance blu-ray video
playback better. This brings the videocard's hardware enhancement features in
line with the new features offered by the latest iterations of the newly
triumphant blu-ray video standard.
ATI/AMD's CrossfireX feature is supported, of course, with provisions for up
to four GPUs; 4 x single GPU videocards or
2 x dual GPU videocards. The Radeon HD 3870 X2 is only compatible
with other videocards in the 38xx series, sadly.
Next up, some serious power consumption values...