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Core Differences From Radeon X1900 XT And XTX Cards

A Tale of Two GTs: Radeon X1900GT by Sapphire and Powercolor
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Here is the sticker on the backof all Radeon X1900 GT cards. Notice that it says "GTO."

While Radeon X1900 GT is the official name given by ATI, the back of both cards we have received havea factory sticker with the name "Radeon X1900 GTO". Oh? We are confirming why ATI and the board makers have this disparity between official and operational nomenclatures, but regardless of naming conventions, the main difference between the XTX and XT versions and the GT are the missing pipelines.

From what we have found, some cards use graphics processors that have lesser than XTX functioning units. Therefore, the non-working sections are disabled to make a whole unit. Some cards have fully functioning units that are disabled. Whether good or bad, there are less pixel shaders running, and the core runs at a frequency of 575 MHz. This is 75 MHz slower than the XTX and 50 MHz slower than the XT. Other than these two major differences, the cores look and perform the same.

Here is the sticker that Sapphire places on the back of the board. With both on the back the card appears to be schizophrenic as each claims it is a Radeon X1900 GTO and an X1900 GT (although there isn't a GTO).
ATI Radeon X1900, X1800, & X1600 Specifications
  X1900XTX X1900XT X1900GT X1800XT X1800GTO X1600XT
Process Technology 90 nm 90 nm 90 nm 90 nm 90 nm 90 nm
Number of Transistors 384M 384M 384M 321M 321M 157M
Core Clocks (Vertex, Core) in MHz 650/650 625/625 575/575 625/625 470/430 440/400
Memory Clock (MHz / data rate) 775/1550 725/1450 600/1200 750/1500 500/1000 690/1380
Vertex Shaders (#) 8 8 8 8 8 8
Pixel Shaders (#) 48 48 36 24 24 12
ROPs (#) 16 16 16 16 16 16
Texture units 16 16 16 16 16 4
Frame Buffer Size 512 MB 512 MB 512 MB 512 MB 512 MB 512 MB
Fetch 4 Yes Yes Yes No No Yes
Memory Bandwidth (GB/sec) 49,6 46,4 38,4 48 32 44,16
Memory Width to Modules 256 Bit 256 Bit 256 Bit 256 Bit 256 Bit 256 Bit
Vertices Second (Millions) 1300 1250 1150 1300 940 880
Pixel Fill Rate (# ROPs x clk) in Billions/sec 10,4 10 9,2 10 6,88 6,4
Texture Fill Rate (# Texture units x clk) in Billions/sec (Times 4 if Fetch4 is present) 41,6 40 36,8 10 7,52 7,04
RAMDACs 400 MHz 400 MHz 400 MHz 400 MHz 400 MHz 400 MHz
Bus Technology PCI Express PCI Express PCI Express PCI Express PCI Express PCI Express

"Oh, a GTO?" For those of you wondering if you can unlock the disabled pipes, which was possible on the Radeon X1800GT, the answer is... maybe. We hate to leave you hanging like that, but as we mentioned before, there are some cores that can't function correctly with all of the units unlocked. This is where we put in the obligatory PSA. Do not attempt this unless you are willing to have a broken video card if it doesn't work!

There are some in the community who have successfully unlocked their cards, and there are also many horror stories. Tofu, a member of the TechPowerUp forums, has been working on graphics BIOS updates to unlock the disabled quad unit. He had an R580 Pro processor version of the card and was able to unlock the pipelines. Subsequently, he ran into problems while tweaking and the card no longer functions.

As it stands, if and only if you have a Pro version of the processor, it is possible to unlock it. While it is similar to the Radeon X1800 GTO, it appears to be a different animal. ATI has confirmed that the graphics processors are R580 cores that have been "yield binned" and earmarked for Radeon X1900 GT graphics cards. "Binned" processors are those that do not meet some standard and have been put to the side until enough were available or the time was right to put them into the market as a new product. Unlike the Radeon X1800 GTO, there were not as many lesser yielding R520 processors and therefore more fully functioning R520 processors were put into Radeon X1800 GTO and thus were able to be unlocked. That being said, it is not at all improbable that future batches of these cards could be made with fully functioning cores. We saw this with Radeon X1800 GTO as Radeon X1900 came on the scene.

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