iPhone 5 A6 SoC Teardown: ARM Cores Appear To Be Laid Out By Hand 178
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.
Why assembly ... (Score:5, Insightful)
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.
Re:A6 hand layout awesome performance sweet (Score:0, Insightful)
Good job Samsung!
For what, exactly reproducing what Apple gave them?
lets look at a different analogy (Score:4, Insightful)
I don't think bicycle riding is a very good analogy to this problem. How about cooking, which is a procedural step-by-step operation? Little hints the recipe can give you like "preheat oven to 350 degrees" can be a tremendous time-saver later. If you didn't know to do that, you'd get your dish ready and then look at the oven (off) and click it on and sit back and wait 20 minutes before placing it in the oven. A dish that was supposed to be 60 minutes start to serve is now going to take 80 minutes due to a lack of process optimization.
Compilers have the same problem of not knowing what the expectations are down the road, and aren't good at timing things. Good expereinced cooks can manage a 4 course meal and time it so all the dishes are done at the right time and don't dirty as many dishes. Inexperienced cooks are much like compilers, they can get the job done but their timing and efficiency usually have much room for improvement.
Automation versus human instinct (Score:5, Insightful)
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.
Re:Automation versus human instinct (Score:5, Insightful)
Re:Automation versus human instinct (Score:5, Insightful)
I think you underestimate how good compilers have become.
I think you may have misunderstood the realities of what a modern expert assembly language programmer does.
An expert assembly language programmer knows when to write assembly language and when not to write assembly language. Assuming that raw performance is the metric by which programmers are judged (which isn't necessarily the case), an expert assembly language programmer will still win over any high-level language programmer because they can also use the compiler.
It's the same with hand-laid-out VLSI. It's not like some team of hardware designers placed every single transistor. That would cause just as much of an unmaintainable mess as writing a large application entirely in assembly language. Rather, the hand-layout designer worked in partnership with the automated tools.