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Sapphire Pure Crossfire A9RD480 There was something we meant to say .. but we forgot
(Review by MS, Dec 22 2005)

There is no denying, the PC-A9RD480 is one of the prettiest boards currently out there, with its white PCB and the red ports, it is definitely an eye-catcher. The layout is very clean with the four memory slots to the right of the CPU socket. All memory slots are in the same color which adds some Tongue-in-Cheek humor to the configuration sticker. In short, for dual channel operation, the modules need to be installed sequentially, that is, slot 1 + 2 or 3 + 4. Depending on the CPU revision the issue of running identical modules may or may not apply.

The expansion slot configuration features two 16 x PCIe slots, with the primary graphics slot being the lower of the two. This is depicted correctly in the manual, however, it deviates from the ATI reference design in which the slots are reversed. This an important point, since the ATI Catalyst Control Center "Help" file points to an ATI document that specifically claims the opposite, namely that a single card needs to be installed in the upper slot, the same goes for the Crossfire Master. Once again, on the PC-A9RD480, the master needs to go into the lower slot. However, it also appears as if in some revisions of the PC-A9RD480 the slot assignment has been switched, in which case, it is the upper slot that needs to be populated first, otherwise, the board will simply not work.

                   

Left to right: x16 PCIe slot and PCI slot configuration, note the EZ-Plug auxiliary Molex connector above the upper PCIe slot. -- The 24 pin EPS power connector is above the parallel ATA connectors at the edge of the PCB -- The ISL 6550CR voltage controller in QFP format -- Zoom-out for the IT8282M next to the ISL6559CR IC -- the actual MOSFETS of the VRM are hidden under a passive heatsink, note the extremely close positioning of the Aux power connector to the VRM -- the ISL 6227 memory VRM controller.

Power and VRM

The main 24-pin EPS connector is placed at the right edge of the PCB, on the far side of the floppy connector, which makes it easy to get the bulky cable strands out of the way. Sapphire recommends a minimum of 500 W PSU, in theory, a 20 pin connector will also work but if there is a choice between a 20-pin ATX and a 24-pin EPS PSU, the latter should definitely be given preference. The CPU is, like on all current board designs, powered through a completely separate power circuitry with its dedicated 4 pin 12V auxiliary supply rail. There is always a debate regarding the positioning of the auxiliary power plug but as a rule of thumb, it should be placed as close as possible to the voltage regulator module (VRM), otherwise, unfiltered 12V power up to roughly 90 W would have to be routed through the PCB where it would create a substantial amount of heat, not to mention the voltage drop caused by the inherent resistance of the traces. In so far, the placing of the connector directly adjacent to the VRM is, from a power management standpoint, the only viable solution. Those who complain about the routing of the four wires may be reminded of cable ties.

Heart of the VRM is the Intersil ISL6559 CR voltage controller chip in a quad flap package, which interfaces with four ISL6612 single phase drivers, each of which in turn drives four MOSFETs. The actual voltage ID signals are generated by ITE's IT8282M "overclock controller". The memory VRM uses its own Intersil 6227 CA dual PWM controller for precision voltage regulation using two integrated synchronous buck DC/DC converters. Clock generation is done by the ICS 951446 clock generator offering a wide frequency range (200-450 MHz for the HT clock) and fixed PCIe frequency.

In case two graphics cards without supplementary (PCIe) power connectors are used in crossfire configuration, an additional EZ-Plug Molex connector just above the upper x16 PEG slot should be connected to the PSU. If the graphics cards already receive dedicated power, this is not necessary and may actually interfere with the board's power distribution.