QL Floppy interface for 1.44MB drives

[lowrybt]

Has anyone encountered in their travels a QL floppy adapter (other than the GC and SGC) that accommodates 1.44MB drives and utilizes the full capacity of HD diskettes? Anyone ever modify a cumana interface to achieve this?

Tom

[tofro]

Tom,

not to my knowledge.

When the Trump Card arrived, it soon grew into "the thing to buy". I think there was no new disk/memory interface after the TC from other vendors. (And TC itself didn't support HD drives).
GC/SGC seem to be the only interfaces that connect to HD/ED drives.

Tobias

[Ralf R.]

In times of the Atari MegaST, there were little PCBs with a WDxxxx plus a chrystal to make them HD compatible. One of these was sold by Jochen Merz. Fitting was quite simple so (in theory) it should be possible to modify a QL Disk Expansion.

Tom,

not to my knowledge.

When the Trump Card arrived, it soon grew into "the thing to buy". I think there was no new disk/memory interface after the TC from other vendors. (And TC itself didn't support HD drives).
GC/SGC seem to be the only interfaces that connect to HD/ED drives.

Tobias

[tofro]

Hmmm. Yes. It should still be possible to do that. Point is, the Atari SMSQ/E already had the HD support built into the drivers. Standard QL disk interfaces haven't. So modifying the controller is only half the work.

• replace the WD1770 on your disk interface (most standard QL interfaces use that) with a WD1772 (you'll probably have to search around a bit for one of those) - WD 1772 is pin-compatible to the WD1770 but can handle HD disk drives.
• Change the clock feed to the FDC from 8 to 16 MHz to enable HD support. If you want to do it right, you should only double the clock speed if an HD drive is detected.
• Patch the disk controller drivers to handle HD disks (more sectors/track)

Would be a major project, I'm afraid (mainly the driver issues, you'd have to disassemble and re-build the driver in ROM).

Tobias

[Ralf R.]

I do not know. What I know is, that I have used (and still have) such a modification in my MegaST4 and there was no need for additional Software or a modified TOS. Just the PCB plus a HD disk drive, that was all. Perhaps TOS was prepared? I do not know, it was the old BlitterTOS.

Hmmm. Yes. It should still be possible to do that. Point is, the Atari SMSQ/E already had the HD support built into the drivers. Standard QL disk interfaces haven't. So modifying the controller is only half the work.

[XorA]

[*]replace the WD1770 on your disk interface (most standard QL interfaces use that) with a WD1772 (you'll probably have to search around a bit for one of those) - WD 1772 is pin-compatible to the WD1770 but can handle HD disk drives.
[/list]

My TC already has a WD1772 in it, no idea if that is original or a later repair though!

I do actually have a stash of WD1772's in my spares

G

[1024MAK]

The later TOS versions included HD support.

Mark

[tofro]

XorA: That means you're halfway there

The Mega ST/E had an (optional?) HD drive, so later TOS versions had to support that.

Unfortunately that doesn't help someone with a QL disk interface.....

Tobias

[1024MAK]

As stated above, it is not just about having or using a WD1772. Extra circuitry is needed.
For HD operation a 16MHz clock input to the WD1772 is needed. In order to remain compatible with DD floppies, the 8MHz clock should be fed to the WD1772 unless the system detects a HD disk is present in the drive. So you also need either a FDD that supplies this signal, or modify a suitable HD drive to supply this signal.

Some IBM PC drives can be used, but they normally need to be modified, as the PC uses a different method to detect the difference between a DD and a HD disk.

Mark

[dilwyn]

There is a circuit diagram from Marcel on my website, showing how he apparently converted a SuperQBoard for HD drive support.
http://www.dilwyn.me.uk/docs/hardware/index.html

Scroll down the page to 'SuperQBoard Modifications' and you'll find a circuit diagram (.PNG files) of the standard DD version and a modified HD version.

Of course, if you're lucky enough to be able to acquire a Gold or Super Gold Card they support HD (1.4MB) and ED (3.2MB QL/2.8MB anything else).