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PCB Design and Cooling System

Developing a simpler and cheaper PCB was a must for the GeForce GTX 260 Core 216 but it is a questionable solution with respect to the GeForce GTX 285. However, Nvidia has indeed come up with a completely revised PCB for the new card.

The PCB is the same length of 27 centimeters, so the single-chip GeForce GTX 285 is no shorter than its dual-chip brother, but we can see it right away that the PCB is completely new. The memory chips have all moved to the face side of the PCB, probably to reduce the number of PCB layers on which factor the manufacturing cost of a PCB depends heavily. As we know, the number of layers has reduced from 14 to 10, which is a good saving. It is especially good considering the high cost of the G200 chip, even in its 55nm version.

More differences can be seen when we remove the cooler:

The new design is somewhat less chaotic in the power section of the card. As opposed to the older PCB of the GeForce GTX 280, the capacitors, power transistors and chokes are all placed in neat rows here. Besides everything else, this should make it simpler to develop nonstandard coolers for the new card.

The GPU voltage regulator has six phases with two power transistors in each phase. There are additional seats on the PCB to add one more transistor into each phase, though. The regulator is based on an Intersil ISL6327 controller, which explains why EVGA’s software tool for increasing the GPU voltage does not yet work with the GeForce GTX 285 as well as with the GeForce GTX 260 Core 216 that employs the 55nm version of the G200 GPU. The current version of that program supports another controller, the Volterra VT1165.

A dedicated dual-phase regulator is responsible for the memory chips. It is controlled by a mysterious chip marked as BR=AK 11E.

Interestingly, both power connectors are of the 6-pin variety whereas the older GeForce GTX 280 used to have one 6-pin and one 8-pin connector and if you plugged a 6-pin cable into the latter, the card would not start up, reporting power problems by means of a red LED. This is just one more indication of the significant reduction in power consumption of the 55nm G200 in comparison with the 65nm version. There is a 2-pin S/PDIF connector next to the power plugs for translating an external audio stream into HDMI.

 
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