Floppy drives on the µPD765

[retro space]

I was testing some disk use with 3,5 inch floppy drives on the µPD765.
I only happen to have HD disks.
If I use a DD drive with a HD disk it does not work
If I use a DD drive with a HD disk with sticker on the hole it does work
If I use a HD drive with a HD disk, it does not work.

I read the controller datasheet, and it seems it can do SD with a clock of 500KHz, and DD with a clock of 1MHz.
I was wondering if you can mod things so it works on a HD drive as well. I don't need HD capacity, but I would like to use HD drives, as they are easier to get. Anybody an idea to get a HD drive going?

[Bryce]

You could try isolating pin 2 (ie: no longer connected to the computer) of the HD floppy drive and connecting the floppy drive side to 5V. This should force the drive to treat the HD floppy as a DD.

Bryce.

[GUNHED]

The FDC765 in the CPC is supplied with 4 MHz. Therefore it can only work with DD discs, but not with HD discs (without patching hardware).

[GUNHED]

I mean "formats", not "discs".

Sadly posts can't be edited here.

[retro space]

The FDC765 in the CPC is supplied with 4 MHz. Therefore it can only work with DD discs, but not with HD discs (without patching hardware).

Can it handle HD at a higher clock (just out of curiosity)?
My idea was to patch the connection to a HD floppy to fool the 765 into thinking it talks to a DD drive.

[Bryce]

It can handle a HD disk with DD format, but most likely not very reliable (read/write failures), but HD format is well outside its capabilities. But even if the 765 could somehow handle it, the data separator circuitry would also need to be tweaked.

Bryce.

[GUNHED]

The FDC765 in the CPC is supplied with 4 MHz. Therefore it can only work with DD discs, but not with HD discs (without patching hardware).

Can it handle HD at a higher clock (just out of curiosity)?
My idea was to patch the connection to a HD floppy to fool the 765 into thinking it talks to a DD drive.

Oh, this interfaces xxxx big time!
Not going to type this all again.

In brief: Yes, the FDC765 (8 MHz) can do that.

Let me know if there is interest in using HD format on CPC with 3,5" floppies, then Hand and me add that to our upcoming expansion - which does only exist as an idea right now. But with the Vortex clone Hans did show how great his work can be. 

[GUNHED]

It can handle a HD disk with DD format, but most likely not very reliable (read/write failures), but HD format is well outside its capabilities. But even if the 765 could somehow handle it, the data separator circuitry would also need to be tweaked.

Bryce.

Well, I'm using HD discs with DD drives on CPC since decades. Even the floppies from the 90ies still work perfect. 

[retro space]

The FDC765 in the CPC is supplied with 4 MHz. Therefore it can only work with DD discs, but not with HD discs (without patching hardware).

Can it handle HD at a higher clock (just out of curiosity)?
My idea was to patch the connection to a HD floppy to fool the 765 into thinking it talks to a DD drive.

Let me know if there is interest in using HD format on CPC with 3,5" floppies, then Hand and me add that to our upcoming expansion - which does only exist as an idea right now. But with the Vortex clone Hans did show how great his work can be. 

Access to regular floppy drives is always welcome, as the physical drives are much easier to obtain.
You say the NEC chip is bad (xxxx)? Do you plan to use something else to interface the drive? I'm curious, because I want to extend the capabilities of my other beloved computer with similar architecture as well.

[GUNHED]

Didn't mean the NEC chip, instead the editor right here. Sometimes it just deletes the whole text one types... 

Will provide further information as soon as the project will advance.