P.A. Semi

» see pasemi.com as it lived, on the wayback machine

~ the goodbye ~

On Monday 21 April 2008, P.A. Semi called its customers to tell them it was being acquired and could no longer guarantee that it would keep supplying them with chips. EDN reported the call that week. Two days later the buyer's name reached the trade press: Apple, for a figure of $278 million that came from a person close to the deal and that Apple itself never put its name to.

The company had been going five years. Daniel W. Dobberpuhl founded it in Santa Clara in 2003 under the name Palo Alto Semiconductor, after a career that included the lead design seat on the DEC Alpha 21064 and on StrongARM. About 150 engineers worked there, and they built one real product.

That product was the PA6T-1682M, a dual-core processor on the Power instruction set. The claim made for it was that nobody outside the alliance that created that architecture had designed a Power core from scratch before. It went into the AmigaOne X1000, a machine built for people who had never accepted that the Amiga was over, and it went into military equipment: EDN wrote that the part had been designed into programs in every major branch of the American armed services.

Apple said essentially nothing in public, beyond confirming to the reporter that it had bought the company and declining to discuss the money. Nothing explained what a buyer who had finished moving the Mac off PowerPC less than two years earlier wanted with a PowerPC design house. The chips stopped being a business in the same week the phone calls went out.

~ the chronicle ~

~ the monday before ~

A chip company telling its customers that supply is no longer guaranteed is telling them to start a redesign, and for an avionics box or a radar processor that is a multi-year job with a recertification at the end of it. Those customers got the warning two days before anybody outside the building knew who the buyer was. EDN reported that P.A. Semi would keep selling the part on an end of life basis, but only if the IBM Power license underneath it could be transferred to somebody else.

By the middle of May the trade press carried reports that Apple would carry on supplying the chip to customers who already had it, with some of the old staff kept on to do the work. How long that actually lasted is not something I can find a source for.

~ performance per watt ~

What P.A. Semi sold was watts. The argument was how much work a core could do for each one it burned, which around 2005 was an eccentric thing to lead with and is now the only thing anybody leads with. It is also why the defense customers turned up. The budget on an aircraft is thermal before it is anything else, and a part that stays cool is worth more up there than a part that benchmarks well on a desk.

I work on compute that has to fly, in Ankara, eighteen years downstream of all this. The constraint has not moved an inch. You are handed a power envelope before you are handed anything else, and every architectural decision after that is an argument with that one number.

~ who they really bought ~

Apple did not buy a chip. It bought a team, which is the only reason anyone still remembers the transaction. Pete Bannon came up through the DEC Alpha work and then P.A. Semi, went to Apple, and spent years running processor design there. Jim Keller had been vice president of engineering at P.A. Semi from 2004 and arrived at Apple in early 2008, close enough to the acquisition that the published accounts disagree about whether he came with it or just ahead of it.

Johny Srouji was a separate hire, recruited from IBM around March 2008, and it was his silicon group that absorbed the P.A. Semi engineers. What came out of that group first was the A4, the processor in the iPad and the iPhone 4, and from that point Apple never shipped another phone running somebody else's application processor. Dobberpuhl himself left Apple around the end of 2009 for Agnilux, which Google bought in April 2010, so the founder outlasted the company by about two years.

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