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Comment by i_don_t_know | Hacker News Reader

I remember seeing a Mandelbrot program for the C64 where half the image was computed on the floppy drive because it's basically the same computer as the main C64. I think it had a 6502 instead of a 6510 and different memory.

I believe the Apple II floppy drive was "dumb", that is, controlled by the 6502 of the Apple II, so the machine couldn't do anything/much while loading/saving data. But the C64 + floppy drive was essentially a two-node distributed system.

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Yeah the Apple II floppy drive read and wrote the sectors using a tight loop of a couple assembly instructions. So yes couldn't do anything at all.

And yet it was like 1/10 the speed of the Apple II floppy drive.

That was because of the slow serial interface on the VIC and C64 side - IIRC, the UART required was removed from the 64 as a cost-cutting measure and it shipped having to bit-bang data to the drive. Overall, this is a very solid design idea.

With a little extra smarts, the drive could deal with ISAM tables as well as files and do processing inside the drive itself. Things like sorting and indexing tables in dBase II could be done in the drive itself while the computer was doing things like updating screens.

OTOH, on the Apple II, the drive was so deeply integrated into the computer that accelerator boards needed to slow down the clock back to 1MHz when IO operations were running. Even other versions of the 6502 would need to have the exact same timings if they wanted to be used by Apple.

The designers planned on using a shift register in the 6522 VIA chips to implement fast serial loading, but an undocumented bug in that chip forced them to fall back to the slow bit banging version that shipped

I don't know how many of you have seen a 1541 floppy drive in person either but it is massive, it's heavier and possibly bigger that an actual Commodore 64 and pretty expensive at the time too.

it's fun seeing c64 people on the defensive about it, a nice change from getting lectures from them about how their graphics were the pinnacle of 8-bit computing

Part of the size was the internal power supply. And that thing got hot, too. I used them at school, but at home only had the smaller 1541-II with an external power brick.

The Apple II disk drives, on the other hand, were not only cheap (Apple was different then!) and fast, but were powered by the ribbon cable connecting them to the computer.

Oh its MUCH better than that. Commodore did this because they had incompetent management. They shipped earlier products (VIC-20, 1540) with hardware defective 6522, but:

- C64 shipped with 6526, fixed version of 6522 without shift register bug

- C64 is incompatible with 1540 anyway

They crippled C64 and its floppies _for no reason_.

It was not for no reason. When adding a screw hole in the motherboard so it could be mounted in the case, they accidentally removed the high speed wire, dooming the C64 to the same slow data speed of the VIC-20 with it's faulty VIA.

The C64 data speed actually ended up being even slower than the VIC-20. You can read the full detailed here: https://imrannazar.com/articles/commodore-1541

ah yes, you're right, they did try to fix it in the C64, forgot that whole part of the story.

They finally got it right in the C128 though!

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