If this kind of stuff interests you, you might want to check into the upcoming “Designed in California” podcast about Apple’s history (still on kickstarter but I think the campaign is over): http://designed.fm. I’ve listened to a few of their preview episodes already, here’s the first one: https://www.youtube.com/watch?v=OsOVyuc1v_w&t=4s
For those who don't know, the Disk II Controller Card is considered by some to be the invention that best demonstrates Woz's genius.
It's also a great early example of the massive win you can get by replacing hardware with software (and "software" -- in the form of a state transition table encoded in a small ROM).
It's also one of the reasons there were so many fascinating and weird copy protections for Apple II software: since so much of the behavior was in software on the computer, it was malleable. (Since it uses the CPU for tight timing loops, the Apple II couldn't really do much else while using the disk.) The write-ups by 4am on IA are fun reading if you're into this kind of thing: https://archive.org/details/apple_ii_library_4am
There are some fun projects to record disks at the level of magnetic flux transitions. I'm mostly familiar with https://applesaucefdc.com by the amazing John Keoni Morris, which came with a new file format too, and some lovely UI software.
As zellyn said, Disk II is pure genius writ large.
It's flabbergasting how good Woz's designs were. Almost on a whim, he with the Disk II did something no one anywhere in Silicon Valley—anywhere in the world—was doing. Forget about IBM, HP, Shugart, Tandon. Just within Commodore and Tandy, Apple's direct 1977 competitors, there were abundant human and engineering resources to come up with a fast, inexpensive, and reliable floppy drive and controller; Chuck Peddle at Commodore was certainly no average engineer. And yet, Commodore was still unable to do this in 1984.
Whether one believes in the reality of the existence of the "10X developer", it's hard not to see what Woz did between 1976 and 1978—Integer BASIC, Apple II color graphics, and Disk II—as proof that such a being can exist, even if (as I have written elsewhere) that brilliance straddled the line between optimized and overoptimized. <https://news.ycombinator.com/item?id=41685888>
Commodore disk drives (4040 and so on) actually use a very similar approach. There's no FDC controller chip and the 6502 is hooked to the drive (literally the same SA-390 as Apple used) via simple hardware. The only significant difference is that the 6502 (actually two of them) is in a separate enclosure from the Pet , communicating via IEEE-488. Since Commodore manufactured the 6502 presumably it was ok to use them liberally.
>Commodore disk drives (4040 and so on) actually use a very similar approach. There's no FDC controller chip and the 6502 is hooked to the drive (literally the same SA-390 as Apple used) via simple hardware.
I disagree that the approaches are similar. The 4040 <https://en.wikipedia.org/wiki/Commodore_4040> is a monstrosity; even the later single-drive models, such as the 1541, are massive. Apple's 1978 floppy drive + Disk II card takes up less space than 1985's 1571 drive (and still significantly faster).
>The only significant difference is that the 6502 (actually two of them) is in a separate enclosure from the Pet , communicating via IEEE-488.
Many things are possible when another 6502 is used just for the drives! That Commodore takes this approach is, as I said, no credit to its army of engineers versus one Berkeley dropout.
>Since Commodore manufactured the 6502 presumably it was ok to use them liberally.
I acknowledge that, had Apple been the owner of MOS and manufactured 6502s, it might also have been tempted to take the easy way out designwise and built Commodore-style drives, or implement the Disk II with a 6502 on it. But I'd like to think that Woz would have done the "right" thing regardless of available resources.
It's also a great early example of the massive win you can get by replacing hardware with software (and "software" -- in the form of a state transition table encoded in a small ROM).
It's also one of the reasons there were so many fascinating and weird copy protections for Apple II software: since so much of the behavior was in software on the computer, it was malleable. (Since it uses the CPU for tight timing loops, the Apple II couldn't really do much else while using the disk.) The write-ups by 4am on IA are fun reading if you're into this kind of thing: https://archive.org/details/apple_ii_library_4am
There are some fun projects to record disks at the level of magnetic flux transitions. I'm mostly familiar with https://applesaucefdc.com by the amazing John Keoni Morris, which came with a new file format too, and some lovely UI software.
It's flabbergasting how good Woz's designs were. Almost on a whim, he with the Disk II did something no one anywhere in Silicon Valley—anywhere in the world—was doing. Forget about IBM, HP, Shugart, Tandon. Just within Commodore and Tandy, Apple's direct 1977 competitors, there were abundant human and engineering resources to come up with a fast, inexpensive, and reliable floppy drive and controller; Chuck Peddle at Commodore was certainly no average engineer. And yet, Commodore was still unable to do this in 1984.
Whether one believes in the reality of the existence of the "10X developer", it's hard not to see what Woz did between 1976 and 1978—Integer BASIC, Apple II color graphics, and Disk II—as proof that such a being can exist, even if (as I have written elsewhere) that brilliance straddled the line between optimized and overoptimized. <https://news.ycombinator.com/item?id=41685888>
I disagree that the approaches are similar. The 4040 <https://en.wikipedia.org/wiki/Commodore_4040> is a monstrosity; even the later single-drive models, such as the 1541, are massive. Apple's 1978 floppy drive + Disk II card takes up less space than 1985's 1571 drive (and still significantly faster).
>The only significant difference is that the 6502 (actually two of them) is in a separate enclosure from the Pet , communicating via IEEE-488.
Many things are possible when another 6502 is used just for the drives! That Commodore takes this approach is, as I said, no credit to its army of engineers versus one Berkeley dropout.
>Since Commodore manufactured the 6502 presumably it was ok to use them liberally.
I acknowledge that, had Apple been the owner of MOS and manufactured 6502s, it might also have been tempted to take the easy way out designwise and built Commodore-style drives, or implement the Disk II with a 6502 on it. But I'd like to think that Woz would have done the "right" thing regardless of available resources.