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.
Even though the Disk ][ was significantly faster than the 4040, the 4040 was significantly faster than the 1541. Apparently the difference was largely due to a bug in the controller used for the Commodore serial bus.
Commodore's 8-bit micros also used IEEE-488 (or a serialized form of IEEE-488) for their floppy drives, rather than a dedicated expansion card that was connected to a bus with direct access to the CPU and RAM. While the expansion bus on the Apple II was fast enough to control the drive directly, the most Commodore could do was send and receive a stream of data to the drive. The drive had to have the smarts to interpret that stream of data. The drive electronics was going to be more complex than Apple's even if Commodore assigned amazing engineers to the task.
Finally, Commodore's approach had its own advantages. Since the drive accepted and handled commands, the CPU could be freed up for other tasks. I don't know how useful that was in general, but the classic example involved two drives autonomously copying floppies. (You could literally remove the cable between the computer and the drives after the operation was setup.) I also recall hearing about classroom setups where multiple computers would share a drive (PET era). It also allowed more drives to be connected to the same bus. Apparently 8 drives were supported. In contrast, the Apple II would support two drives per expansion slot.
They were really slow though. It took minutes to boot up a game from the 1541. I never had one but my friends did, and one of them had a "Fast Load Cartridge", which I believe just replaced the software on the drive and on the computer with better software that was something like 5x as fast.
... which is still significantly slower than the Disk II.
The 1978 Disk II is about 30 times faster than the unaccelerated 1982 Commodore 1540/1541, as well as more reliable,[1] cooler-running,[2] and just more elegantly designed. The same comparison holds for the 4040 and other pre-1541 Commodore drives, albeit with the speed disadvantage vis-a-vis Apple being less.[3]
[1] The 1541's drive head often goes out alignment despite both it and Disk II using similar "ratatatat" methods to return to the first track. Also, the first couple of years of 1541 production were notorious for failures in general.
[2] As the 1541 is a standalone 6502-based computer with an integrated power supply, overheating is constantly an issue.
[3] Yes, the 1541 is slower than earlier Commodore drives, because of the move from parallel to serial IEEE-488 and a hardware bug (that both necessitated and allows for Fast Load and its counterparts)
The bottleneck was with the serial protocol between the drive and C64. It was done via bit banging in software due to some chip bug. The fastloaders replaced the protocol with something more amenable to bitbanging.
It wasn't really the hardware's fault though. It was crippled by Commodore's marketing department wanting to maintain compatibility with the VIC-20's 1540 FDD, which meant that the bit banging method used to work around a bug in the VIA chip had to be used. Then to add insult to injury, because of how the VIC-II and 6510 need to share the bus, it ended up running even slower than the VIC-20.
That's very much missing the point. It's absolutely true that the "approach" was similar (the bit encoding was software-generated in a timing loop and fed to non-ASIC hardware to send to the drive).
But the Disk II card was 8 chips you could get from Radio Shack, where the 8050 was a monster with a whole CPU/memory/bus (you can see the board appear in this video at 1:15 https://www.youtube.com/watch?v=S3d2cNSAB9A&t=69s).
And Woz's was faster. And hit market almost two years earlier. There's an aesthetic judgement to be made here too, and... it's not remotely close.
There are few in the same category, perhaps Widlar or Gilbert for pure analog circuit design, or Bill Atkinson in later Mac software? It's a very short list.
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.
Even though the Disk ][ was significantly faster than the 4040, the 4040 was significantly faster than the 1541. Apparently the difference was largely due to a bug in the controller used for the Commodore serial bus.
Commodore's 8-bit micros also used IEEE-488 (or a serialized form of IEEE-488) for their floppy drives, rather than a dedicated expansion card that was connected to a bus with direct access to the CPU and RAM. While the expansion bus on the Apple II was fast enough to control the drive directly, the most Commodore could do was send and receive a stream of data to the drive. The drive had to have the smarts to interpret that stream of data. The drive electronics was going to be more complex than Apple's even if Commodore assigned amazing engineers to the task.
Finally, Commodore's approach had its own advantages. Since the drive accepted and handled commands, the CPU could be freed up for other tasks. I don't know how useful that was in general, but the classic example involved two drives autonomously copying floppies. (You could literally remove the cable between the computer and the drives after the operation was setup.) I also recall hearing about classroom setups where multiple computers would share a drive (PET era). It also allowed more drives to be connected to the same bus. Apparently 8 drives were supported. In contrast, the Apple II would support two drives per expansion slot.
... which is still significantly slower than the Disk II.
The 1978 Disk II is about 30 times faster than the unaccelerated 1982 Commodore 1540/1541, as well as more reliable,[1] cooler-running,[2] and just more elegantly designed. The same comparison holds for the 4040 and other pre-1541 Commodore drives, albeit with the speed disadvantage vis-a-vis Apple being less.[3]
[1] The 1541's drive head often goes out alignment despite both it and Disk II using similar "ratatatat" methods to return to the first track. Also, the first couple of years of 1541 production were notorious for failures in general.
[2] As the 1541 is a standalone 6502-based computer with an integrated power supply, overheating is constantly an issue.
[3] Yes, the 1541 is slower than earlier Commodore drives, because of the move from parallel to serial IEEE-488 and a hardware bug (that both necessitated and allows for Fast Load and its counterparts)
But the Disk II card was 8 chips you could get from Radio Shack, where the 8050 was a monster with a whole CPU/memory/bus (you can see the board appear in this video at 1:15 https://www.youtube.com/watch?v=S3d2cNSAB9A&t=69s).
And Woz's was faster. And hit market almost two years earlier. There's an aesthetic judgement to be made here too, and... it's not remotely close.