Also, they turned the bad chips from fabs into keychains - with all the CPU Circuitry revealed behind a dollop of clear epoxy - had that as my keychain for nearly a decade.
Core memory is really cool - and just in case you like some of this https://www.reddit.com/r/cableporn/ is a good place...
I'd love to having something like that again. Do you know if it is possible to acquire these? I tried googling but I'm coming up short, I can't find the right search terms.
Like what is the failure rate during manufacture, and what is actually happening when something goes wrong on the assembly line?
It's quite common in cpu manufacturing -- called "yield" (how many good cpus you get):
"Once the front-end process has been completed, the semiconductor devices are subjected to a variety of electrical tests to determine if they function properly. The proportion of devices on the wafer found to perform properly is referred to as the yield. Manufacturers are typically secretive about their yields, but it can be as low as 30%. Process variation is one among many reasons for low yield"
https://en.wikipedia.org/wiki/Semiconductor_device_fabricati...
If that's remotely true, and their product offer/lineup is built around the failure rates, single-core CPUs would have resulted in staggering numbers of failures, since a single defective core meant a trashcan rather than a down-SKU.
(If the original supposition is true, then it's highly likely GPU, flash, ram etc work on the same principle. Anywhere you have a die with multiple repetitive units, where a die with less units still has market value, it seems like a sensible way to recoup value on what would otherwise be discards.)
I don't think all defective chips were DOA. A core that is stable at 1000MHz would be a Pentium 4 and another sample of the exact same chip that catches fire at 1000MHz but is stable at 500MHz would be a Celeron (etc).