Seems like if you're going to reverse an obscure chip, something with a more exotic application would have been more fun?
It had the downside of requiring precise timing. This is an issue if you wanted a faster (or even a slightly improved) 6502 in the machine.
Oh well...
No, the Disk II was absolutely a masterpiece. Go back to the linked article, think about everything this very complicated chip did, and recognize that Woz made a card that did exactly the same thing out of 6 chips you could buy at Radio Shack and two tiny ROMs.
https://en.wikipedia.org/wiki/Apple_II_accelerators#Zip_Chip...
For example I was driving a GSM Modem (over serial) which contained a comparatively advanced ARM SoC driving it.. from an AT Mega 8-bit micro that I was programming. It was great educationally, but kindof hilarious :)
It's microcontroller all the way down.
Fun fact: It's also how those fake FTDI FT232 chips on the gray market were made. Counterfeiters just picked a cheap general-purpose microcontroller in mass production and wrote a Mask ROM for it. What's funny is that, the counterfeit chips actually have better process node than the real one (it doesn't mean it's better, though).
https://zeptobars.com/en/read/FTDI-FT232RL-real-vs-fake-supe...
https://twitter.com/marcan42/status/695292366639378433?s=19
Don't buy FTDI chips; their malicious driver incident that bricked clones (by exploiting another bug in the EEPROM write support in their own chips!) should be enough to convince every board designer to stay away from them.
Many of these clones have their own quirks, and the amount of work-arounding that's been added to the Linux drivers is quite notable. Kernel 8.5 onwards seems to incorporate most of the fixes, but along the way, patches like this were available:
https://gist.github.com/nevack/6b36b82d715dc025163d9e9124840...
Despite the fantastic efforts of the driver maintainers, I still managed to find a "CSR 4" cheap dongle that threw all sorts of errors in the logs and didn't work. I'm waiting for some Broadcomm chip-based replacements to arrive.
The PC-AT's use of the keyboard controller to control A20 and CPU reset comes to mind.
Any others?
Having dabbled in both MCS-48 and 6502 assembly I can tell you it was probably not done to make software development easier. :) I suspect maybe the hardware was just easier to design around a microcontroller? ...but there could have been other reasons...
When they realized what they had done, it was too late.
As for the older systems, does anyone have a date for the WD 1771 (the more common alternative)? The data sheet shown on the Wikipedia page is dated April 1979, and if that’s the release date then it would have been a new, unproven part compared to the intel chip when the System and Atoms were released 1979/80, assuming the floppy drive was an early upgrade (again, I don’t have dates to hand).
[1] http://chrisacorns.computinghistory.org.uk/8bit_Upgrades/Aco...
(I find Google Books very useful for this sort of archaeology. Change the time range to "1977-1980", search for "wd1771", and then sort by date. Of course this isn't thorough, but it gives a good overview for little effort.)
But at the same time it's no surprise that later models switched over to the cheaper and more technically capable chip.
Home decapping is possible, from what I can tell, but uses methods like “fuming nitric acid” and “blowtorch”, neither of which I would really want to experiment with right now.
resilicon.reddit.com is becoming fairly active, if you have an interest.
