Unholy interspecies floppy experiment

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Joined: Jul 5 2018 - 09:44
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Unholy interspecies floppy experiment

I'm not sure if this fits here...  But I finally pulled the trigger on one of the bigger pieces of what I need for something that will probably make both Apple and Commodore purists cringe...


A while back I bought an Apple IEEE-488 interface...  Today I bought a Commodore 4040 dual floppy drive...


All I need to get now is the proper cable to hook them together...


Then it should just be a matter of writing a little code to make them talk...


I'm pretty sure it can be made to work because someone posted a video of a //e booting from an HP IEEE-488 3.5" floppy drive a while back.  And in the past I built a  Commodore Serial Bus card for the Apple II that could talk to a Commodore 1541 drive, which I understand uses a similar software protocol even though the hardware interface is different.


macnoyd's picture
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Joined: Oct 15 2012 - 08:59
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Curious ...

What does the Commodore offer (via floppy) that Apple doesn't already have?

Or, is this simply a technical challenge?

Last seen: 2 hours 32 min ago
Joined: Jul 5 2018 - 09:44
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It's a technical challenge

It's a technical challenge mostly.  The Commodore drive is dual single sided single density drives.  They use GCR, albiet a slightly different way.  It stores 170k on each side of a floppy.  It is very similar to two 1541 drives, although not write compatible, and much faster because of the IEEE interface which is parallel instead of serial.  Unlike the Apple drives, this one has it's own 6502 and (small amount) of RAM.  Their OS is on ROM on the drive.


The reason I developed the Commodore Serial Bus interface card for the Apple II back in the 1980s was to facilitate copying files back and forth between the two systems.  It was much more convenient than the way the guy I designed the card for had been doing it, which was by a 300bps modem.  Commodore 64s pretty much sucked for any kind of serial interface because their serial functions were implemented by bit-banger functions using two pins off of one of the 6526 parallel chips used in that system.  Because of that, they struggled to even do 1200bps throughput, and you needed some kind of 1488/1489 or MAX232 card for them to do RS-232 anyway.  That was his other choice, to get that and use a null modem cable to transfer the files to his //e.  The CSB card in the Apple II with the 1541 hooked up could copy files much quicker.


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Joined: Aug 14 2020 - 07:01
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This one is very cool. Can't

This one is very cool. Can't wait to see how it turns out

 I've got one of these cards as well and am looking forward to interfacing shenaigans in the future ;)


Keep us posted !





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