LONDON–The A6 processor at the heart of the Apple iPhone 5 smartphone uses an ARM-compatible processor core rather than the
Cortex-A15 processor core licensed from ARM Holdings plc, according to a prominent semiconductor analyst.
The theory, proposed in a report by Linley Gwennap, principal analyst at the Linley Group, contradicts an earlier report by a financial analyst firm that the A6 is a dual-core Cortex-A15 processor manufactured for Apple by Samsung in its 32-nm HKMG process technology.
Gwennap agrees that Samsung is the probable manufacturer of the A6. But he speculates that the chip is the result of an ARM architectural license believed to have been taken by Apple to complement the 2008 acquisition of fabless chip firm P.A. Semi.
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In an online article,
Gwennap points out
that iPhone 5 applications have to be recompiled to a new instruction
set architecture variant called ARMv7s. This, he says, supports the theory that A6 includes custom processing cores. It certainly proves
that A6 does not use the same Cortex-A9 cores that are in the Apple
A5 processor, according to Gwennap.
The ARMv7s instruction set architecture is reportedly
compatible with the Cortex-A5, Cortex-A7 and Cortex-A15. But Gwennap says it supports the theory of a custom processor.
"We believe the custom A6 CPU is similar in complexity and performance
to Cortex-A15 as well as to the Krait CPU that appears in Qualcomm's
newest processors. To reach Apple’s claim of a 2x performance gain over
the iPhone 4S (which uses the Apple A5 processor), we expect the A6
contains two CPU cores clocking at roughly 1.2GHz," states Gwennap in
Qualcomm is an architectural licensee of ARM
(Cambridge, England). So, while Krait is similar in performance to the
Cortex-A15, it is substantially self-designed while remaining compatible
to the ARMv7 instruction set.
Gwennap believes that in 2008 Apple set its newly-acquired IC design team off on two projects; a near-term team to quickly develop processors around licensable ARM cores to create the A4 processor and a longer-term team to use the architectural license, which has resulted in the A6 processor.
Analysts at Nomura Equity Research speculated in a report earlier this month that the A6 is a dual-core Cortex-A15 manufactured for Apple by Samsung on a 32-nm HKMG manufacturing process. The firm offered no source for the speculation.
I would contend that the difference between a custom core from Apple and the Cortex-A15 from ARM may not be the black and white choice it is at first glance.
It was anandtech that first came out with the "speculation" that the A6 has some in house cores rather tahn A15. Linley and others are merely embellishing in that. Best to wait till someone like Chip works does a teardown on iPhone 5 and carries out a similarity analyses with SoCs following pure ARM designs - like Samsung's Exynos in the S3.
First die shots are over on anandtech. Confirms dual arm cores. Also confirms 3 gpu cores (543MP3). Now where is that techinsight article that was posted here a few days back that stated the gpu was being switched to Mali ?
If this is true, then it would be PASemi teams first product - after 4 years! That is a long time for this much hyped acquisition to be paying dividends and after all that the performance is comparable to the A15? That is a shame.
David Patterson, known for his pioneering research that led to RAID, clusters and more, is part of a team at UC Berkeley that recently made its RISC-V processor architecture an open source hardware offering. We talk with Patterson and one of his colleagues behind the effort about the opportunities they see, what new kinds of designs they hope to enable and what it means for today’s commercial processor giants such as Intel, ARM and Imagination Technologies.