Closer Look at the Radeon X1900-Series: PCB Design and Cooling System
The new RADEON X1900 XT/XTX doesn’t look much different than the RADEON X1800 XT at first:
The PCBs of the RADEON X1900 and X1800 are not identical, but a careless observer may be misled into supposing that the new graphics cards from ATI use the older PCB design.
Take a look at the rear part of the card where the power circuit is placed: this section is fully populated, from top to bottom, on the RADEON X1900 XT. There are 5 switch transistors and 5 inductance coils on the RADEON X1800 XT (but there exist versions of the card with more of these elements installed) and one set of seats is left empty. There are 7 such seats on the RADEON X1900 XT and all of them are occupied because the R580 consumes more power than the R520.
The reverse side of the PCB shows appropriate changes, too. It carries more tiny capacitors and there is a seat for an additional power element near the memory chips, which is not soldered in, though. With the cooler removed, you can also see a power controller chip in about the same spot, but on the face side of the card, along with a MOSFET and some smaller elements. We guess this circuit is responsible for powering the memory chips. A multi-channel Volterra VT1103 controller is still the heart of the power circuit of the card.
And this is where the difference between RADEON X1900 and RADEON X1800 ends: the left parts of the PCBs are identical. The wiring of the PCB of the RADEON X1800 ensures stable operation of the GPU and memory at high clock rates, so ATI had no need to design a completely new PCB from scratch. We’d like to remind you that most top-end graphics processors are pin-compatible, so graphics card manufacturers may try to use the same PCBs for the R520 and R580. But considering the higher power requirements of the new chip and the constant evolution of PCBs, we suppose that the RADEON X1900 PCB may be used for some RADEON X1800-based products, but not vice versa.
The same is also true for the RADEON X1900 CrossFire Edition which too differs from the RADEON X1800 XT CrossFire Edition in the power circuit only. We didn’t find any differences in the design of the Compositing Engine which we described thoroughly in our new review of ATI CrossFire technology.