At long last, Apple released Intel’s highly anticipated Sandy Bridge updates on both the MacBook Air and Mac mini earlier this month. However, many of these machines – along with the 13″ MacBook Pro introduced earlier this year – rely solely on Intel’s integrated graphics, a move that raised eyebrows among users allergic to the reduced performance that often comes with Intel’s integrated GPUs. The move from Intel’s integrated GPU from the 320M indeed has some trade-offs, but some investigation reveals that performance is, as we suspected, largely the same.
While Intel’s reputation for graphics hasn’t gone much beyond “just barely enough to suffice,” the integrated GPU in Sandy Bridge processors represents Intel’s first serious effort to address performance. That performance generally compares to low-end discrete GPUs, while in many cases reducing overall power consumption.
We thought it would be useful to examine the differences between Apple’s previous integrated solution – the 320M – and Intel’s HD Graphics 3000. Given that Intel’s next-generation architecture, codenamed Ivy Bridge, is expected to offer significantly improved graphics, we can draw some conclusions about why Apple decided to make the switch now rather than later.
Previous low-end machines from Apple paired an Intel Core 2 Duo processor with an NVIDIA controller that had an integrated GPU. Such controllers combine functions of northbridge and southbridge typical in older PCs, including RAM access, I/O, and other functions, as well as integrated graphics. The first controller Apple widely adopted across its computer line was the 9400M, which included a 16-core GPU that ran at a nominal speed of 580MHz, and was good for 54Gflops of processing power.
Apple later adopted an improved version of this controller dubbed the 320M. This part was made exclusively
for Apple, though there are similarities with NVIDIA’s 310M mobile solution. This Apple-only variation had 48 shader cores at a nominal speed of 450MHz and was good for roughly 130Gflops. (Neither Apple nor NVIDIA would confirm the speed to us, but it is estimated from what little information is public about the 320M.)
With the 9400M and later the 320M serving as a baseline, Apple began architecting its operating system and many of its software applications to rely more and more on the capabilities of the GPU to optimize performance. Apple also pushed for a standardized way for programmers to leverage GPU and other processing power for performance enhancements, and worked with multiple vendors to implement the Open Compute Language, otherwise known as OpenCL. The standard, largely based on NVIDIA’s GPGPU language CUDA, was finished just in time for Apple to wrap support for it into Snow Leopard.
Unfortunately for Apple (and perhaps NVIDIA), Intel disputed NVIDIA’s legal standing to build controllers for its post-Core 2 Duo processors. That meant if Apple wanted Intel’s new Clarkdale or Arrandale processors, it would have to use Intel controllers. Ultimately, Apple decided to move some of its machines to these new processors and combine them with discrete GPUs, largely from NVIDIA. For Apple’s most compact models, however – including the 13″ MacBook and MacBook Pro, MacBook Air, and Mac mini – the company was left with two options: rely on the decidedly lackluster performance of Intel’s integrated graphics, or stick with older processors and NVIDIA’s 320M.
The latter is exactly what Apple did.