5 ms·
Die size isn't really about packing more cores into a CPU. it's about packing more CPUs on a wafer. The material cost is the largely the same. Smaller die si
by da_chicken 11y ago
Die size isn't really about packing more cores into a CPU. it's about packing more CPUs on a wafer. The material cost is the largely the same. Smaller die sizes are about your quality control with masks and deposits.
Given a 300mm diameter wafer and a 10mm square CPU die at 14nm you get about 700 CPUs per wafer (Pi * diameter * diameter) / (4 * die * die) (https://en.wikipedia.org/wiki/Wafer_(electronics)#Analytical_die_count_estimation https://en.wikipedia.org/wiki/Wafer_(electronics)#Analytical...). If you change that 10mm CPU to 10nm, you'll have about a 7.2mm square CPU die. That's nearly 1400 CPUs per wafer. Even if you get 100% of CPUs from the 14nm die, once your yield hits 50% on 10nm the 10nm process produces more for the same cost. Now you can either reap the profits, or reduce costs.
- nightcracker 11y agoI'm no expert, but isn't there another technique in play as well? As you get smaller you can duplicate CPU components to make your chip fabrication more robust against errors. If a component is faulty on the die, the CPU can be patched to use the other (identical) component.
- Animats 11y agoThe Cell did that. They really had 9 Cell processors on the chip, but only 8 of them were enabled on any given PS3. Patching at a lower level has been tried, but it's usually more trouble in manufacturing than it's worth. There's a long history of workarounds for low yield, but the fab industry has usually been able to fix the fab problems and get the yield up. Except for memory devices, where patching out bad columns is standard.
- bravo22 11y agoThat only works for things like on-board SRAM
- monocasa 11y agoThis is done in quite a few places including GPUs.
- TheLoneWolfling 11y agoUnfortunately, you end up having to make the interconnects longer to accommodate the additional redundant components, which ends up slowing everything down. It's a tradeoff that's not always worth it.