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Generally, yes, a failing transistor can be a fatal problem. This relates to "chip yield" on a waferfull of chips. Faults don't always manifest themselves as
by mchannon 11y ago
Generally, yes, a failing transistor can be a fatal problem. This relates to "chip yield" on a waferfull of chips.
Faults don't always manifest themselves as a binary pass/fail result; as chip temperatures increase, transistors that have faults will "misfire" more often. As long as this temperature is high enough, these lower-grade chips can be sold as lower-end processors that never in practice reach these temperatures.
Am not aware of any redundancy units in current microprocessor offerings but it would not surprise me; Intel did something of this nature with their 80386 line but it was more of a labeling thing ("16 BIT S/W ONLY").
Solid state drives, on the other hand, are built around this protection; when a block fails after so many read/write cycles, the logic "TRIM"s that portion of the virtual disk, diminishing its capacity but keeping the rest of the device going.
- ajross 11y ago> Am not aware of any redundancy units in current microprocessor offerings Sure there are. That's why Intel sells chips with a thousand different cache sizes, for example. Bad bit in the cache? Just turn that block off. Likewise for whole cores in some of the bigger chips, I believe.
- frik 11y agoThe Xbox360 had four cores (IBM Power) but only three cores were enabled. And older AMD CPUs were released with 6 enabled cores out of 8 cores.
- GTP 11y agoWow, that's interesting! Do you know if somebody tried to enable one of this "extra cores"?
- jotm 11y agoHaha, of course they did. http://www.tomsguide.com/forum/id-2142984/amd-phenom-710-4th-core-unlock.html http://www.tomsguide.com/forum/id-2142984/amd-phenom-710-4th... AMD used to software-disable the 4th core on the Phenoms, but then they switched to disabling them by hardware, so that rendered any software means useless. AMD only disabled the cores to save on manufacturing - most of the time, these cores were not working properly. But as the process got better, people got 4 or more cores for the price of 2-3 :-D
- jevinskie 11y agoThe PS3 disabled 1/8 SPUs for yield and you can try to reenable it: http://ps3devwiki.com/ps3/Unlocking_the_8th_SPE http://ps3devwiki.com/ps3/Unlocking_the_8th_SPE Good luck if it turns out the disabled SPU is actually bad!
- ixtli 11y agoI seem to recall the ps4's Cell shipping with 2 out of 8 cores disabled because of the failure rate per wafer.
- scott_s 11y agoI spoke with the project lead for the XBox 360 chip, and I asked him: Why three cores? It's a strange number. He said it was to make Christmas.
- provemewrong 11y agoAMD was particularly fond of selling dual and even tripple core CPUs that were quad core chips with some cores disabled. And people where unclocking these cores for profit, because they speculated that AMD disables core for the whole batch even if it was a single unit from it that failed the test, so there could be possibly plenty of good cores disabled along the way.