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Price is proportional to die size. Processing one wafer is a fixed price, so the more chips you can fit on one wafer, the cheaper each individual chip. Additio

by pg314 9y ago

Price is proportional to die size. Processing one wafer is a fixed price, so the more chips you can fit on one wafer, the cheaper each individual chip. Additionally, the number of defects is proportional to the area. The bigger your chip, the more chips you will have to throw away because of defects. E.g. say you have one defect per wafer on average, if your chip takes up the whole wafer, you will have no good chips. If you can fit 100 chips on one wafer, you will have 99 good ones and one bad one.

jlebrech 9y ago
yes, i'm aware. but i'm sure the "processing cost" also factors in R&D to get to that node size up to that point. you also don't need to double the die size just double the size of the package (what AMD seem to have done), that way you can swap broken dies out.
- darkmighty 9y ago
  Correct me if I'm wrong, but I don't think AMD physically swaps out defective cores. I believe they're disabled individually in some kind of firmware. That's effective because the interconnect region is significantly smaller than the core area (and possibly made more reliable through feature size manipulation?). I think this has been standard practice almost dating back to multi-core introduction, where they sell high end multi-core chips as low end with some cores disabled.
  - gsnedders 9y ago
    Note parent was talking about die and not cores. AMD are shipping multi-chip modules with ThreadRipper (with two die) and EPYC (with four), and then because they are separate die you can trivially swap them out.
    - jlebrech 9y ago
      i believe this is a way for them to maximise yield, say their threshold is at least 3 dies must be good, and only 1 can be passable, then when they do tests and only 2 are good, they can swap out one of the passable ones, they can also rate the cpus differently too, they could also just swap out dies when all fail the test, i.e with threadripper and replace with another 2, then rate those.

by pg314 9y ago

jlebrech 9y ago

yes, i'm aware. but i'm sure the "processing cost" also factors in R&D to get to that node size up to that point. you also don't need to double the die size just double the size of the package (what AMD seem to have done), that way you can swap broken dies out.

darkmighty 9y ago
Correct me if I'm wrong, but I don't think AMD physically swaps out defective cores. I believe they're disabled individually in some kind of firmware. That's effective because the interconnect region is significantly smaller than the core area (and possibly made more reliable through feature size manipulation?). I think this has been standard practice almost dating back to multi-core introduction, where they sell high end multi-core chips as low end with some cores disabled.
- gsnedders 9y ago
  Note parent was talking about die and not cores. AMD are shipping multi-chip modules with ThreadRipper (with two die) and EPYC (with four), and then because they are separate die you can trivially swap them out.
  - jlebrech 9y ago
    i believe this is a way for them to maximise yield, say their threshold is at least 3 dies must be good, and only 1 can be passable, then when they do tests and only 2 are good, they can swap out one of the passable ones, they can also rate the cpus differently too, they could also just swap out dies when all fail the test, i.e with threadripper and replace with another 2, then rate those.