A Tale of Two GTs: Radeon X1900GT by Sapphire and Powercolor

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Core Differences From Radeon X1900 XT And XTX Cards

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.

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ATI Radeon X1900, X1800, & X1600 Specifications
Row 0 - Cell 0	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.