What is the technical reason that standard HD floppy drives don't work on cpc? Is there any known solutions to make them work? Herbals a 4 drives mx4 board?
The reason is quite simple as to why the HD floppy drives don't work to their full capability is that the CPC data transfer speed is to slow for the drive to READ/WRITE to enable the high capacity.
To get 1.44 MB floppies to work is the CPC would need a faster Z80 and change to the clock feeding the u765 (disk controller). The controller is fed the 4MHz clock and this limits the transfer speed to the physical drive while the Z80 is to slow to feed the u765 the data to enable higher transfer rates.
I understand but a microcontroller card offloading the actual load would likely be possible. Then I guess why not use cp link and a usb drive on the pi. Make a unidos node for it.
Quote from: zhulien on 22:56, 20 June 23I understand but a microcontroller card offloading the actual load would likely be possible. Then I guess why not use cp link and a usb drive on the pi. Make a unidos node for it.
With that effort, you can also access mass storage. What benefit will HD floppies have there?
I sometimes need to read floppies on my cpc... admittedly more often 3" discs. Might be best to try get a fd1 working but the cabling at least on ebay is so expensive
Well, there is just one thing to be done: Double the crystal speed rate for the FDC765, then you can work with HD floppies too. Of course this needs some adaptions on the CPC's mainboard. And it's questionable if this is desired.
The Z80 itself is fast enough to handle HD floppies, that's not the problem. Of course this needs proper coding
BTW: My Desktop CPC runs a 5,25" HD floppy with DD disquettes.
Quotefd1 working but the cabling at least on ebay is so expensive
I ended up purchasing 34 pin connectors from aliexpress and making my own ribbon cables instead of getting them from ebay. Only need a vice to squeeze the connectors on
https://www.aliexpress.com/item/4000232542115.html
Aneasier option would be to get an Amiga 4000 HD floppy drive. The Amiga chipset also had problems accessing HD floppies (which need to read and write the data twice as fast) and so they did it in a different way: the made the drive spin slower (150 RPM instead of 300) when using HD floppies.
But it would be sad to separate an Amiga 4000 from its original disk drive for this.
Now unfortunately this is going to be rather vague as hardware isn't really my thing.....
About two years ago I read an article in a old WACCI from a member who had built an interface for HD disk drives.
All I can remember is that it was connected to either the printer or expansion port with a cable also connected to the 2nd drive port on a 6128. A software program of 2K was also mentioned but how it operated I simply don't know.
When I run across the article again I'll have it scanned and uploaded to the Wiki but no guarantee when that will be.
WACCI:
https://www.cpcwiki.eu/index.php/WACCI