SUMMARY: SiS has been known in history for their less-than-stellar line of graphics chips for past several years now. With new R&D tactics SiS has braved the 3D front once again with the Xabre GPU. Breathtaking products from SiS have been few and far between, but some of the latest SiS products have been receiving good press, does the Xabre have what it takes to compete with the nVidia GeForce 4 MX460 in the value/mainstream market place? Read on as Cameron "Sov" Johnson gives us an answer!
The SiS Xabre GPU was an overnight popup. Nothing was really known about the GPU until its official press release from SiS. Now that this has happened we don't have to speculate, we have our facts.
The Xabre is a totally redesigned 256-bit 3D chip which supports what SiS calls "8x8" functions. The first "8" represents the support for the AGP 8X interface and the second "8" for DirectX 8.1 support. The Xabre carries a third generation T&L unit. This new engine supports Pixel Shaders 1.3 in hardware utilizing a 29 programmable instruction set, making it one of the most powerful T&L engines available.
While carrying the best T&L engine there is, however, one major problem; there is no hardware vertex shaders, only a software vertex shader that can be emulated by the CPU. This fact alone does reduce on paper the power of the Xabre quite a bit, as vertex shaders are being used quite a bit lately.
While the CPU lacks the Vertex engine, SiS has added a few new features that on paper help improve quality of the CPU for the low budget 3D accelerator. The Frictionless Memory Control, or FMC, is a method SiS uses to boost effective memory bandwidth and improve overall memory efficiency by adding extra filters into the memory paths to allow smoother and much better ECC than other video controllers.
The Coloredeemer Technology is something which enhances color rendering of the displayed images. Additionally, the chip's MotionFixing Video processor provides crystal clear video images with four methods of de-interlacing. Their anti-aliasing method, known as Jitter-Free Anti-Aliasing, provides 1X, 2X, and 4X full scene anti-aliasing (FSAA) without the jagged frames of other 3D accelerators.
SiS provides a link layer for those lovely extras such as TV out, DVI and Dual Monitor technologies, which SiS has named Dual Scene Technology. The principals of this are the same as nView. You can have duplicate desktops on two displays, merged displays where half turns up on both monitors or you can have dual desktops - This is where one program appears full screen on one monitor and another comes up on a second monitor, very handy. All these features have been bundled into the SiS 301 controller chip which accompanies just about all Xabre cards.
At the moment there are currently three different Xabre cards -The Xabre 80, Xabre 200 and Xabre 400. Xabre 80 runs an engine/Core clock of 200/166Mhz and only uses AGP4x protocols. Xabre 200 runs a core/memory clock of 200/166, same as the 80 only this chip has AGP8x support, this will ultimately give the Xabre 200 a slight lead over the 80. Xabre 400 is the high end of the SiS 3D family with a core/memory clock of 250/250 on an AGP8x bus. This is a rather slow clock speed for a 0.13 micron die, so we should see faster core speeds from SiS very soon I would imagine.
Below you will see a block diagram of the SiS Xabre CPU which should give you a basic idea of how the Xabre itself works.
