Apple purchase of Intrinsity confirmed
So the rumor is true, and Apple has indeed bought Intrinsity. Apple confirmed to The New York Times today what Linkedin profile updates have already indicated, with Intrinsity's employees naming Apple as their new employer. As for the price, NYT cites MPR's Tom Halfhill, who claims that the purchase price was $121 million. Halfhill has been around the processor scene since forever, and he has great sources, so this number is probably in the ballpark.
As for what Intrinsity brought to Apple that PA Semi couldn't, the answer is a CPU core. Samsung and Intrinsity announced the Hummingbird core in the summer of 2009, and this is almost certainly the core on which Apple's A4 is based. Hummingbird is a ground-up, cycle-accurate, high-performance remake of ARM's Cortex A8 architecture, done by Intrinsity and Samsung in order to get the A8's clockspeed comfortably up to 1GHz on a 45nm process. The following description from the PR is fairly clear in laying out what Intrinsity did with Hummingbird:
Intrinsity's Cortex-A8 processor-based FastCore embedded core is cycle-accurate and Boolean equivalent to the original Cortex-A8 RTL specification. While most ARM processor cores are implemented with synthesized static logic and compiled SRAMs, the Hummingbird achieves the exceptional 1GHz clock rate in Samsung's 45nm LP process technology through the use of a semi-custom design flow which strategically applies Intrinsity's proprietary Fast14 1-of-n domino logic (NDL) technology as macros in the timing-critical paths of the Cortex-A8 RTL core.
Hummingbird also has a variable-sized L2 cache, so that a customer can size a particular part's L2 in order to fit their transistor budget and performance needs.
The fact that Hummingbird is the A4's core explains the mysterious "extra transistors" found by Chipworks in their recent teardown. Intrinsity did a lot of custom logic for the A8 in order to get it up to 1GHz while minimizing leakage current and dynamic power, and that logic might have involved making some tradeoffs in transistor count—i.e., the Intrinsity design could be a little larger than a standard A8 because the company found different optimization point between on-die footprint and power usage.
The A4's Hummingbird implementation may also have a larger L2 than the standard A8, which would also bloat its transistor count. A fatter L2 would make a great deal of sense, because it would improve the performance of the in-order core on the kinds of branchy integer workloads that you find in Web and productivity apps.
Given that Intrinsity and Samsung collaborated on Hummingbird, and that Samsung also has some SoC designs based on the core, it makes sense that A4 was fabbed on Samsung's 45nm SoC process. This means that Apple is basically just a typical Samsung foundry customer who mixed IP blocks from a number of different vendors, Samsung included, into a custom SoC design that Samsung now makes. Other customers could license those same blocks from Samsung (the Hummingbird "A8" CPU), Imagination Technologies (the PowerVR GPU), and others who haven't yet been disclosed, and make their own A4 competitor that would match the A4's performance and power efficiency profile quite closely. Once again, this means that Apple's edge with the iPad is not in the processor or the hardware, but in industrial design and software.
If the Intrinsity team actually stays together and keeps working on Apple mobile parts, however, Apple will have the potential to really differentiate itself from the rest of the ARM ecosystem. In a few years, Apple could have very fast, proprietary versions of the CPU and GPU cores that power its products.