4 ms·

I'd say randomly guessing that 1/3 of processors are useless is pretty out there. I'm sure Sony has smarter process than that.

by bpicolo 13y ago

sp332 13y ago
It's not randomly guessing, it's comparing to defect rates in other 28nm processes. An example: if you have 30 chips per wafer and 3 defects per wafer, you get 90% good chips. But if you have only 10 big chips per wafer with the same defect rate, now you get only 66% good chips.
objclxt 13y ago
It's not a random guess - it might surprise you just how low the yield actually is on CPUs. Yield is inversely proportional to die size, so the larger the die, the lower the yield. Yield is also lower on newer manufacturing processes. Both apply here. Furthermore, although some chips might be only marginally defective and 'binned' to a lower SKU that option isn't open to Sony. They have no use for those lower-clocked chips. Chip manufacturers never publish their yield figures, but if you look around you'll see yields of around 60% are certainly not uncommon or unheard of.
- grecy 13y ago
  > They have no use for those lower-clocked chips. Could they be selling them to someone else? i.e. if the GPU is binned to a lower SKU, could they be selling it to someone else that's then throwing it onto a regular PCI-e card for a desktop?
  - wmf 13y ago
    There is no product on the market with similar-but-slightly-lower specs to the PS4 chip.
- pa5tabear 13y ago
  Are you sure about that? My background is limited but my understanding is that chip makers will set their spec limits far higher than need be. The chips then get tested, and those that struggle at the higher frequencies will be designated as the lower end processor. Or those which have a single low speed core will be designated as "tri-core" processors. I know these practices wouldn't apply too well when you're making a PS4 with a single performance level, but that 60% yield still sounds horrible from a process design perspective.
  - icegreentea 13y ago
    Well, it depends on how you measure 'yield'. 60% yield at hitting "high-spec" could easily mean 90% yield at "low-spec".
- wmf 13y ago
  Caches and GPUs have extra capacity that is used to tolerate defects. Cell had 8 SPEs but shipped with 7 working. It's possible that the PS4 has 20 CUs and ships with 18 working; this would increase yield dramatically. (Update: Yep, 20 CUs: http://www.chipworks.com/en/technical-competitive-analysis/resources/blog/ps4-core-processor/ http://www.chipworks.com/en/technical-competitive-analysis/r... )

I'd say randomly guessing that 1/3 of processors are useless is pretty out there. I'm sure Sony has smarter process than that.

by bpicolo 13y ago

I'd say randomly guessing that 1/3 of processors are useless is pretty out there. I'm sure Sony has smarter process than that.

sp332 13y ago

It's not randomly guessing, it's comparing to defect rates in other 28nm processes. An example: if you have 30 chips per wafer and 3 defects per wafer, you get 90% good chips. But if you have only 10 big chips per wafer with the same defect rate, now you get only 66% good chips.

objclxt 13y ago

It's not a random guess - it might surprise you just how low the yield actually is on CPUs. Yield is inversely proportional to die size, so the larger the die, the lower the yield. Yield is also lower on newer manufacturing processes. Both apply here. Furthermore, although some chips might be only marginally defective and 'binned' to a lower SKU that option isn't open to Sony. They have no use for those lower-clocked chips. Chip manufacturers never publish their yield figures, but if you look around you'll see yields of around 60% are certainly not uncommon or unheard of.

grecy 13y ago
> They have no use for those lower-clocked chips. Could they be selling them to someone else? i.e. if the GPU is binned to a lower SKU, could they be selling it to someone else that's then throwing it onto a regular PCI-e card for a desktop?
- wmf 13y ago
  There is no product on the market with similar-but-slightly-lower specs to the PS4 chip.
pa5tabear 13y ago
Are you sure about that? My background is limited but my understanding is that chip makers will set their spec limits far higher than need be. The chips then get tested, and those that struggle at the higher frequencies will be designated as the lower end processor. Or those which have a single low speed core will be designated as "tri-core" processors. I know these practices wouldn't apply too well when you're making a PS4 with a single performance level, but that 60% yield still sounds horrible from a process design perspective.
- icegreentea 13y ago
  Well, it depends on how you measure 'yield'. 60% yield at hitting "high-spec" could easily mean 90% yield at "low-spec".
wmf 13y ago
Caches and GPUs have extra capacity that is used to tolerate defects. Cell had 8 SPEs but shipped with 7 working. It's possible that the PS4 has 20 CUs and ships with 18 working; this would increase yield dramatically. (Update: Yep, 20 CUs: http://www.chipworks.com/en/technical-competitive-analysis/resources/blog/ps4-core-processor/ http://www.chipworks.com/en/technical-competitive-analysis/r... )