ATI RADEON HD 2900 XT 1024MB

Does 2900XT really need 1GB of memory?

We understand why AMD doesn't allow to sell cards like HD 2900 XT 1GB. Even after our first article of this series it was clear that the problem was not in memory capacity - 512 MB of memory was quite sufficient even for top graphics cards. There is nothing wrong with memory bus width either. The problem is in the core.

Our tests proved that the first driver bundled with the first card sample significantly raised performance at the expense of other card features. By "other" we mean antialiasing. Alas, there is evidently a bug in the GPU, since it does not allow the core to process AA as it would normally do. But the idea was brilliant! Expand the memory bus to 512 bit, so that AA is processed almost for free! Pity, but we can already state the fact that the card does not need 512 bits of bandwidth, because it's not utilized at 100%. The company got around this bug rather smartly - drivers are used to force ALUs process AA. That is, AA is actually emulated, which takes up much shader resources and affects overall speed - all our tests prove it.

Now, imagine this product with 1024 MB of memory instead of 512 MB. What does it give us? Not much. OK, memory performance is increased, because memory frequency is raised from 830 MHz to 1000 MHz. Memory bandwidth is increased. But will it help the gimpy AA mode? I think if you pay US$550 for this product, you have the right to demand normal AA operation. All AMD programmers are currently optimizing the drivers to minimize these losses.

But the cards are already in stores and people buy them. So we are very curious: what will 1GB of memory give to this product? And does it make sense to overpay $100 for it? (MSRP of HD 2900 XT 512Mb is 449 USD, MSRP of 1GB card is 549 USD. The latter is not set by AMD, however, but by its partners. As I have already mentioned, the chip maker strongly objects to retailing these cards and insists they are manufactured only for OEM and system builders. All HD 2900 XT cards are manufactured by AMD/ATI's orders at third-party plants. Partners of the American-Canadian company have nothing to do with their manufacturing, they just buy ready cards from AMD.

Nevertheless, AMD is well aware that all partners will want to sell these cards, OEM or not, especially if cards are refused by system builders. Besides, the latter themselves might want to get rid of surplus (which usually goes to the gray market).

All right, now let's proceed to the examination of the graphics card, which was kindly provided by our readers (and that's very pleasing!) This product bears markings of Sapphire and gets to stores via its sales channels.

Graphics card

ATI RADEON HD 2900 XT 1024MB PCI-E

GPU: RADEON HD 2900 XT (R600) Interface: PCI-Express x16 GPU frequencies (ROPs/Shaders): 742/742 MHz (nominal - 750/750 MHz) Memory frequencies (physical (effective)): 1000 (2000) MHz (nominal - 1000 (2000) MHz) Memory bus width: 512bit Vertex processors: - Pixel processors: - Unified processors: 320 Texture processors: 16 ROPs: 16 Dimensions: 220x100x32 mm (the last figure is the maximum thickness of a graphics card). PCB color: red RAMDACs/TDMS: integrated into GPU Output connectors: 2xDVI (Dual-Link), TV-Out. VIVO: RAGE Theater 200 TV-out: integrated into GPU. Multi-GPU operation: CrossFire (Hardware).

ATI RADEON HD 2900 XT 1024MB PCI-E
The graphics card has 1024 MB of GDDR4 SDRAM allocated in sixteen chips on the front and back sides of the PCB. Samsung memory chips (GDDR4). 0.8 ns memory access time, which corresponds to 1250 (2500) MHz.

Comparison with the reference design, front view
ATI RADEON HD 2900 XT 1024MB PCI-E	Reference card ATI RADEON HD 2900 XT

Comparison with the reference design, back view
ATI RADEON HD 2900 XT 1024MB PCI-E	Reference card ATI RADEON HD 2900 XT

This card will be NO DIFFERENT from its modification with twice as little memory. It just uses memory chips of higher capacity, that's all. No more changes.

The R600 requires a much more complex PCB compared to the R580 (X1950 XTX) because of the twice as wide memory bus. Nevertheless, the manufacturer tried to keep the card no longer than previous solutions and to equip it with a proper cooler (with normal dimensions).

Owing to very high power consumption (above 200 Watt) the card has two power connectors. One of them is a 8-pin connector (PCI-E 2.0) instead of the usual 6-pin one. There are presently no adapters for this connector. That's OK, because a usual 6-pin cable from a PSU can be plugged into this connector, and the remaining two pins are responsible for unlocking overclocking (the driver determines whether these pins are powered, if no - it blocks any attempts to raise frequencies).

The card has TV-Out with a unique jack. You will need a special adapter (usually shipped with a card) to output video to a TV-set via S-Video or RCA. You can read about TV Out here. We should also note that all top cards from ATI are traditionally equipped with VIVO (including Video In to convert analog video to digital form). This function is based on RAGE Theater 200 here instead of the traditional Theater:

We should mention sterling HDMI support. The card is equipped with its own audio codec, which signals go to DVI. So the sterling video-audio signal goes through a special bundled DVI-to-HDMI adapter to an HDMI receiver.

We can see that the card is equipped with a couple of DVI jacks. Dual link DVI allows resolutions above 1600x1200 via the digital interface. Analog monitors with d-Sub (VGA) interface are connected with special DVI-to-d-Sub adapters. Maximum resolutions and frequencies:

• 240 Hz Max Refresh Rate
• 2048 x 1536 x 32bit @ 85Hz Max - analog interface
• 2560 x 1600 @ 60Hz Max - digital interface