3 ms·
Modern designs sometimes have some duplication of functional units that allow the final chip to be configured in a workable manner even if a few of the units do
by retrac 5y ago
Modern designs sometimes have some duplication of functional units that allow the final chip to be configured in a workable manner even if a few of the units don't turn out right. But otherwise, getting all of those transistors working right is the big challenge of chip design. Yes, they all have to work. Yields on new processes are often very low, only a fraction of the devices made actually working.
- 7373737373 5y agoDoes anyone know more detailed articles about how this (self-)checking architecture/process works?
- henrikeh 5y agoThe book “VLSI test principles and architectures: deign for testability” edited by Laung-Terng Wang et al, is quite good.
- retrac 5y agoI'm afraid I don't have any articles to direct you to. I can give you a little detail of how they do it with RAM. DRAM is just a huge array of cells. The array itself is made up of repeated sections of a block. These blocks are independently wired and have on-die logic for testing (simple memory check). The blocks which pass testing are configured by blowing fuses so they're connected to the normal input/output logic, and the broken ones have fuses blown to disconnect them from the power rails. They slightly overbudget the number of blocks when designing. This way if a few blocks are faulty they still have a working RAM chip. If a whole bunch of blocks aren't working, they can still sell it as a half- or quarter-capacity chip. A 8, 16 and 32 gigabit RAM chip in the same process from the same manufacturer may well have the same die inside, with different fuses blown. This isn't new; it's been done since at least the 1980s. It's my understanding the same thing is done with cache and cores and even execution units on modern processors, but I would assume with a great deal more complexity.