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> We build 8 core CPUs and blow e-fuses in the factory to make them 4 cores. Not "deliberately". We build 8-core CPUs, discover four of them are a bit sub-spec
by Gordonjcp 4y ago
> We build 8 core CPUs and blow e-fuses in the factory to make them 4 cores.
Not "deliberately". We build 8-core CPUs, discover four of them are a bit sub-spec, and blow e-fuses to disable those and sell it as 4-core. It's possible that those four disabled cores would be just fine, but I'm not selling you a chip that gets its sums wrong sometimes.
I guess people complained about how chip manufacturers sold CPUs rated at 25MHz that could be overclocked to 33MHz, but they too were not guaranteed to meet spec even if they worked.
- nonrandomstring 4y agoIs it really the case that dies/packages are tested and batched individually? I mean, you make a good point on reliability/quality, but there are surely cases where to create a product differential perfectly good (and known to be good) devices are crippled. That seems ever less ethically defensible as we move into scarcity.
- Gordonjcp 4y agoDepends on the value. If you test half a dozen off a die and they're all sub-spec, they're all binned the same even if some are okay. This is why overclocking used to work - if even a small proportion of the chips tested were good to 25MHz, that was a 25MHz batch, guaranteed good to 25MHz. If you got a "lucky penny" that'd go to 33MHz as per the design spec, then good for you! But it wouldn't be guaranteed to do that.