Apple's A6 Architecture Unveiled, Unique Design, 3 GPUs, Samsung Manufactured
You read that right, and if you've been following the geekier side of the mobile scene for some time, this is hardly shocking. Samsung built the ARM-based A5 processor found in the iPhone 4S, as well as the A5X chip powering Apple's third generation iPad tablet. It's just business, after all, and now Samsung is supplying A6 parts for the iPhone 5, as the engineers at Chipworks confirmed in a highly detailed teardown with wonderful product shots of the actual die.
2) and has "APL0589B01" etched into the lower left corner. That's quite a bit bigger than Samsung's second generation 32nm A5 chip, which measures 8.19 mm by 8.68mm.
If you're not versed in CPU design, don't worry yourself, the annotated interesting parts are rather obvious, not the least of which is the dual-core ARM portion. What makes this so interesting is that the layout appears to have been done by hand, a relative rarity these days. If we zoom into the one of the three A6 GPU cores, we can see what a standard layout looks like:
Standard cell blocks on the A6 GPU core
Custom tuned cell blocks of ARM core in A6
It looks quite a bit different, doesn't it? That's because Apple's large team of engineers, laid out the ARM cores by hand. This is a pretty strong indication that the A6 is a custom-tuned designed, a rarity these days and potentially the reason why Apple is able to extract such great performance while maintaining modest die size and power consumption.
"Normally large digital blocks of logic use automated 'place and route' CAD software to layout all the digital cells and connect them," Chipworks explains. "This is the style used on the rest of the digital blocks on this chip. This is also the style that has been used for the CPUs in all previous Apple iPhone and iPad processors. However, on this A6 chip, the ARM core appears to have been laid out by hand. This does lend credence to the current thinking that this is a custom ARM core specifically designed for the A6."
It's not too often you find custom laid out digital cores. Part of the reason is because, like anything else, doing it by hand takes a longer time. It's also more expensive, so why go that route? The upside to laying out cores by hand is that they typically result in faster maximum clock rates, and in some cases, higher density, Chipworks explains.
Another theory is that Apple ran into a problem somewhere along the way, and rather than push back the iPhone 5's release date, it had engineers come in design a custom layout. Whatever the reason, the end result is a piece of hardware that's both incredibly fast (read our review of the iPhone 5 to see it smoke top Android phones in benchmarks) and fascinating to behold.