Slashdot Mirror
iPhone 5 A6 SoC Teardown: ARM Cores Appear To Be Laid Out By Hand
MrSeb writes "Reverse engineering company Chipworks has completed its initial microscopic analysis of Apple's new A6 SoC (found in the iPhone 5), and there are some rather interesting findings. First, there's a tri-core GPU — and then there's a custom, hand-made dual-core ARM CPU. Hand-made chips are very rare nowadays, with Chipworks reporting that it hasn't seen a non-Intel hand-made chip for 'years.' The advantage of hand-drawn chips is that they can be more efficient and capable of higher clock speeds — but they take a lot longer (and cost a lot more) to design. Perhaps this is finally the answer to what PA Semi's engineers have been doing at Apple since the company was acquired back in 2008..."
Pretty picture of the chip after using an Ion Beam to remove the casing. The question I have is how it's less expensive (in the long run) to lay a chip out by hand once instead of improving your VLSI layout software forever. NP classification notwithstanding.
The question I have is how it's less expensive (in the long run) to lay a chip out by hand once instead of improving your VLSI layout software forever. NP classification notwithstanding.
Coding in assembly still remains a superior method of squeezing extra performance out of software. It's just that few people do it because compilers are "good enough" at guessing which optimizations to apply, and where, and usually development costs are the primary concern for software development. But when you're shipping hundreds of millions of units of hardware, and you're trying to pack as much processing power in a small and efficient form factor, you don't go with VLSI for the same reason you don't go with a compiler for realtime code: You need that extra few percent.
I like to view things as a little more complicated than just applying optimizations. IMHO assembly gets some of its biggest wins when the human programmer has information that can't quite be expressed in the programming language. Specifically I recall such things in the bad old days when games and graphics code would use fixed point math. The programmer knew the goal was to multiply two 32-bit values, get a 64-bit result and right shift that result back down to 32 bits. The Intel assembly programmer knew this could be done in a single instruction. However there wasn't any real way to convey the bit twiddling details of this fixed point multiply to a C compiler so that it could do a comparable operation. C code could do the calculation but it needed to multiply two 64-bit operands to get the 64-bit result.
The question I have is how it's less expensive (in the long run) to lay a chip out by hand once instead of improving your VLSI layout software forever.
No matter how much improvement on VLSI layout software their output can't match that of hand-laid layout by those who know what they are doing.
The VLSI layout software are like compilers. The final compiled code relies on two factors - the source-code input and the built-in "rules" of the compilers.
A similar case is in software programming - The source code from a so-so programmer compiled by a very very good compiler will result in a "good-enough" result.
It's good enough because it gets the job done.
However, a similar program by an expert Assembly Language programmer would have left "good enough" behind because the assembly language programmer would know how to tweak his code using the most efficient commands, and cut out the 'fats" by optimizing the loops and flows.
Muchas Gracias, Señor Edward Snowden !