Apple change of strategy?

With all of the recent chatter regarding the disappearance of Intrinsity from the technology community, a question opens up about the strategy of the company that has in all likelihood bought them: Apple.

It all started with the announcement of the Hummingbird processor by Samsung - see my January 27th post about the ipad for a link in the comments to the press release surrounding the Samsung/Intrinsity collaboration to create a 1GHz implementation of the ARM Cortex-A8 processor.

When the iPad was announced, and the clock speed was said to be 1GHz, and it runs the iPhone OS, and the timescale was about right for Hummingbird to be in production, it was clear that the great performance of this hardware is in part down to the excellent implementation skills possessed by Intrinsity, since this chip is in all likelihood an exact match for a Hummingbird enabled System on Chip (SoC).

So why would Apple buy Intrinsity? I think the answer lies somewhere between their need for full custom silicon across the board (including at the processor RTL micro-architectural level), and the need to proceed quickly to market with the fastest possible implementation of off-the-shelf components, built in a semi-custom manner using Intrinsity's techniques.

Intrinsity possess a mix of technology and knowhow that allows them to do a really good job of making designs operate faster. They create a custom version of a given off-the-shelf processor design that addresses the slowest paths through the chip, and then adds special fast logic into those paths to speed them up. This makes the logical path between the clocked elements of the processor shorter, allowing the clock to run faster.

Because a strategy that focusses around Intrinsity relies on feeding them with other people's silicon designs (they do not actually design anything - they customise the generic design descriptions for fast operation in a given semiconductor companies process node), this suggests to me that Apple might be continuing with their use of ARM's licensable processor IP for the foreseeable future.

If Apple sticks with optimising off-the-shelf components in ways that other people cannot - now that they own Intrinsity - what does this say about their suspected ambitions towards designing their own in-house ARM processor?

I think the answer is two-fold.

Firstly, Apple are getting good performance out of ARM's "soft" cores by being clever in how they are implemented. This is quite low-hanging fruit, since the whole design and verification task has been done by ARM in creating the CPU in the first place. The "only" thing Intrinsity would have to do is identify the areas of the design that were holding back the top-end frequency, and make optimisations to those for speed.

Secondly, it isn't easy designing a processor from scratch. I believe that Apple retain a large percentage of the CPU design talent that they obtained from PA Semi - it would only have been the top-brass involved in business development that would have left to form Agnilux (now bought by Google). However, PA Semi's last ARM implementation would have been the experience gained from working on StrongARM at DEC and the ARM architecture has certainly moved on to include many new features. For an architect to get up to speed on that, and then work out what the CPU will look like is non-trivial, and bringing a team up to scratch on how to build that - and verify it - is not a two year task. It can take up to 4 years to turn around a CPU from scratch, especially if you've not worked with the architecture either for a long time, or on it's latest incarnation.

It also opens the question of what Apple thinks they can achieve over and above what ARM can achieve in CPU design? ARM are experts at designing their own CPUs, and have a spectrum of nifty high-performance implementations available in the applications CPU space. Give or take wanting a CPU with better performance or lower power, I can only think that Apple have decided to take their time on designing their own processor, and will stick for the foreseeable couple of years using optimised ARM macrocells.

If/once Apple do successfully complete the creation of their own CPU, the Intrinsity guys would then be deployed to analyse it, and make its implementation go faster. However, if you have that many in-house implementation engineers working alongside your designers, it would be possible to feed information to the designers about where the worst paths were in the design, and get them shortened before moving from the design description into the synthesis and layout stages of the project. This to some extent negates the value of having Intrinsity on board, because their skills lie in taking a pre-verified box off-the-shelf that you cannot change in any way, and making logically equivalent cycle accurate implementations of it that are faster and possibly lower power than if they were just synthesised automatically into standard bulk-CMOS. As such, it is a little bit questionable how much of Intrinsity's unique abilities can co-exist with the presence of an in-house design team, and what percentage benefit can be gained by using Domino logic on a design that is as fast as it can be in its RTL implementation.

So I've said it before in a previous post and it is worth repeating here - PA Semi designed CPUs in Apple devices will take many years to appear. Now I can add that they will only be marginally faster than what opther companies are capable of now that Intrinsity co-exist alongside a design team working towards a common cause. Just where I think Apple's own processor designs might wind up appearing in the product line is a matter for another post. But one thing is sure - Apple are intent on crafting their own silicon, and the game is changing still.