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.
Apple bought P.A.Semi for $278 million in cash in April 2008. Soon
after the acquisition, ARM announced the signing of an architectural
licensing deal with an unnamed "strategic OEM." There was speculation at
the time that the licensee was Apple.
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.
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