PCB Design and Functionality

The product copies the reference design. Covering the entire face side of the card, the cooler’s plastic casing looks very pretty:

Well, tastes differ, and gamers’ tastes differ, too. The card measures 267x111x32 millimeters.

As opposed to its predecessor GeForce GTX 280, the GeForce GTX 285 has no memory chips on the reverse side of the PCB and no cap above them.

The card has the same interfaces as its predecessor. It plugs into a PCI Express x16 2.0 slot and is equipped with two dual-link DVI-I connectors and one S-Video output. There is a vent in the card’s mounting bracket for the hot air to be exhausted out of the system case.

There are connectors for building SLI (or 3-way SLI) configurations in the top part of the card’s PCB.

A 6-pin power connector is now installed instead of an 8-pin one because the GeForce GTX 285 has lower power requirements due to the thinner GPU tech process. According to the specs, the reference GeForce GTX 285 has a peak power consumption of 183W (53W lower than that of the GeForce GTX 280). A 550W or higher power supply is recommended for a computer with this graphics card.

The card’s PCB differs greatly from the GeForce GTX 280. Nvidia’s engineers had had to make the PCB design simpler and cheaper in order to reduce the manufacturing cost and they succeeded.

Besides moving all the memory to the face side of the card, the engineers revised its power section:

The 55nm GT200-350 chip was manufactured in Taiwan on the 48th week of 2008.

Judging by its marking, the chip is revision B3. This GPU incorporates 240 unified shader processors, 80 texture-mapping units and 32 raster back-ends. Thus, it is no different from the GPU installed on the GeForce GTX 280 (GT200-300) but thanks to the thinner tech process its frequencies are increased from 602/1296MHz to 648/1476MHz (+7.6/14.0%). The XFX GeForce GTX 285 (GX-285N-ZDFF) has the same frequencies as the reference sample although XFX already offers accelerated models with specially selected chips and factory overclocking. The GPU frequencies are reduced to 300/600MHz in 2D mode in order to save power and reduce heat dissipation.

The GeForce GTX 285 is equipped with 16 chips of 0.77ns GDDR3 memory from Hynix. The total amount is 1024 megabytes.

These H5RS5223CFR N3C chips are rated for a frequency of 2600MHz but clocked at 2484MHz in compliance with the GeForce GTX 285 specs. Although this is 12.2% higher than the memory frequency of the GeForce GTX 280, the chips can work faster still. I will check this out in an overclockability test shortly. The memory bus is 512 bits wide. The card lowers its memory frequency to 200MHz in 2D mode.

Let’s take a look at the card’s specs:

Take note that the GPU-Z tool reports that the GPU is revision B1 and has a manufacture date of January 2009 although the GPU’s marking clearly says revision B3 and the 48th week of the last year.  Otherwise, there are no discrepancies.