Gallium3D LLVMpipe On The Sandy Bridge Extreme
A thorough performance look at the Intel Core i7 3960X "Sandy Bridge" Extreme Edition processor will be published very soon, but in this article are some benchmarks of using Gallium3D's LLVMpipe driver on this six-core processor with Hyper Threading.
When running the Core i7 3960X at 4.5GHz, we see the best performance out of LLVMpipe ever for lightweight OpenGL games, but still this open-source Mesa/Gallium3D software fallback driver isn't useful aside from a debugging utility for driver developers or as a software fallback for modern Linux desktops, as will be found in Fedora 17 for handling the GNOME Shell when no GPU hardware drivers are available.
For those not familiar with LLVMpipe, it is an open-source Gallium3D driver used as a software fallback for running OpenGL off the CPU when GPU hardware acceleration is not available. This software fallback is faster than the other choices (namely the classic Mesa software rasterizer and Gallium3D swrast) since it uses LLVM for run-time code generation. Key processes are implemented in LLVM IR with this software rasterizer and then translated to machine code. Speeding up things a bit is that the driver is multi-threaded and can take advantage of other modern CPU features like SSE3/SSE4 support through its use of the Low-Level Virtual Machine. It was only recently that it became possible to use LLVMpipe with GNOME Shell after GLX_EXT_texture_from_pixmap support was added by Google to this driver, among other work. It can also be used by the Wayland Display Server. The first widespread use of this driver was as the software acceleration method in Fedora 15.
The LLVMpipe performance is compared to a low-end Radeon HD 5450 graphics card with the AMD Catalyst 11.11 proprietary driver. Due to an issue on Monday, there are not LLVMpipe numbers to publish when the Sandy Bridge-E CPU was running at its stock speeds. The i7-3960X has a base frequency of 3.3GHz and 3.9GHz Turbo Boost. The six-core CPU also has 256KB of L2 cache per core and 15MB of shared L3 cache while sporting a quad-channel DDR3 memory controller. Like the other Sandy Bridge CPUs, it is built on a 32nm process and offers other similar functionality like SSE4.2, AES-NI, and AVX extensions. Intel sent out the i7-3960X and their DX79SI motherboard as Linux review samples to Phoronix for these products that were just released in November.
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