[Ken Shirriff] is no stranger to Hackaday. His latest blog post is just the kind of thing we expect from him: a tear down of the venerable 8008 CPU. We suspect [Ken’s] earlier post on early CPUs pointed out the lack of a good 8008 die photo. Of course, he wasn’t satisfied to just snap the picture. He also does an analysis of the different constructs on the die.
Ever wonder why the 8008 ALU is laid out in a triangle shape? In all fairness, you probably haven’t, but you might after you look at the photomicrograph of the die. [Ken] explains why.
He also explains a bit about how PMOS works and the history of the design, including why it was in the odd 18-pin package. At the end, he talks about how he decapsulated the part and got the pictures, in case you ever want to try that yourself.
As a personal aside, I used to do this at Motorola and I think [Ken] was wise to stick to the ceramic packages since you can mechanically decapsulate them. With an epoxy part, you can use a Dremel or similar tool to mill out some epoxy (just don’t go too deep), put the chip on a hot plate (a copper bar helps carry the heat up to the package), and then fill the milled cavity with fuming nitric acid. But you shouldn’t be doing that without a lot of protective equipment including vent hoods, safety showers, and experience storing, handling, and disposing of nasty acids. I have a feeling [Ken] could pull it off, but it isn’t something you just want to try on a whim.
[Ken] has done this kind of thing before. If you are wondering what kind of computer you could build with such a tiny device, we just saw one the other day. Of course you already saw [Ken’s] talk about his process at this year’s SuperCon, right?