PCB Design and Specifications
Despite its rather modest specs and positioning in the $129-149 price category, the Radeon HD 2600 XT is about as large as a Radeon X1950 Pro and has a much more complex wiring than GeForce 8600 GT/GTS. The PCB owes its large size not only to the area occupied by the power circuit but rather to the position of the GPU.
Although the card doesn’t have a 6-pin PCI Express connector, its power circuit is rather complex. Some of its elements are not installed, though. There is a seat for the mentioned connector, too, but there is an electrolytic capacitor there instead. The circuit is controlled by a chip marked as “uP6201AQ”. We couldn’t find a description of it.
Following the modular design principle ATI had used before, the power circuit occupies almost the entire back part of the PCB. It is sharply separated from the rest of the PCB, which helps cut the cost of developing new PCBs. For example, for a card with a higher level of power consumption it is only necessary to change the design of the power circuit, leaving the rest of the PCB intact, and this will be cheaper than developing a completely new PCB.
The power circuit of the Radeon HD 2600 XT seems to dissipate quite a lot of heat as it provides cooling for the load-bearing components as opposed to GeForce 8600 GT and GTS cards. This gives us apprehensions about how much power the new card needs. It cannot require more than 75W, which is the load capacity of the PCI Express slot, but may need more than the GeForce 8600 GTS requires.
The graphics core is placed rather far from the DVI connectors and this area of the PCB is almost empty, except a seat for a VIVO chip which is not installed.
Although the RV630 chip incorporates 101 million transistors more than the G84, its die area is smaller thanks to the thinner 65nm tech process. The die is square and installed in a compact package without a protective frame. The marking on the chip doesn’t indicate that it’s an RV630. Our sample is dated the 19th week of 2007 (mid-May). Judging by the marking, this is a fifth revision of the RV630 core.
The GPU is not divided into domains working at different frequencies. All of its subunits are clocked at 800MHz. The GPU has 120 unified shader processors grouped into 3 large computing modules, 2 large texture processors roughly equivalent to 8 ordinary TMUs, and one rasterization module equivalent to 4 classic ROPs.
The Radeon HD 2600 XT should be able to carry 512 megabytes of graphics memory, so there are 8 seats for memory chips on the PCB, 4 of which are rather unusually on the reverse side of it. The discussed version comes with GDDR4 memory and has four Samsung K5U52324QE-BC09 chips on the face side of the PCB. Each chip has a capacity of 512Mb (16Mbx32), 1.8V voltage for all the circuitry, and a rated frequency of 1100 (2200) MHz. This is indeed the frequency the memory is clocked at by the card. The four chips provide a total of 256MB of graphics memory accessed across a 128-bit bus. The 512MB version of the card has a 128-bit memory bus as well.
Like the R600, the R630 chip has a full-featured frame compositing engine, making the Radeon HD 2600 XT capable of working in a CrossFire tandem. The card has two standard CrossFire connectors for that purpose. The Radeon HD 2600 XT, the senior model of the series, can output audio over the HDMI interface via an appropriate adapter (included with the card). The integrated audio solution supports PCM (16 bits, 32/44.1/48kHz) and AC3 (Dolby Digital and DTS) formats.
The overall PCB design of the Radeon HD 2600 XT isn’t ideal in our eyes. The graphics card is rather too big for its class. It may not fit into some compact system cases.