exxos's Atari, Amiga & retro forum

Yes, I see you're quite right about the AJAX in the Atari 1.44MB upgrade manual, Rubber_Jonnie.
Probably a safeguard against overheating in case HD floppies are used a lot.

As I have two Sony MPF-920 drives which have both been "Atari modified" but won't work in my STe ("Data in drive may be damaged" error message after attempting to read a floppy) I decided to remove the Atari modifications and try them out in the MSTE. Alas that didn't help, so I assume this means that not all revisions of this particular drive work with the MSTE either (just like they don't all work with normal STs).

Next I opened up the drive which actually does work with the MSTE: a Sony MPF-520-1 (1/131) to see if it was modified or not (yes, it was).
So I removed the wire across the disk detect (CTIN) switch pins, then removed the wire which went from one pin of the HD-detect (HDIN) switch to pin 2 of the 34-pin ribbon-cable connector.
The drive still worked the same way as before, both with HD and DD floppies. Mind you, I haven't done any extensive testing, but should I keep the drive unmodified for the MSTE (apart from having the "drive select" connection soldered to "DS0" instead of the factory-installed "DS1")?
I did notice that when a floppy has been read and I press ESC it'll re-read the floppy. As far as I remember, with my STe it won't re-read the floppy unless you've ejected it in the meantime (i.e. the computer thinks you've changed the floppy), but the MSTE might be doing media change differently.

Can anyone confirm this, or if I should put one (or both) drive modifications back?

Sony MPF-920 need no patches or mod in a Mega STE only set to ds0

OK, thanks.

And the media change -is it normal for the MSTE to read the floppy again (start the motor) every time you press ESC, with the same floppy disk?

Pacman wrote: 12 Apr 2021 12:37 OK, thanks.

And the media change -is it normal for the MSTE to read the floppy again (start the motor) every time you press ESC, with the same floppy disk?

I just tried it on my MSTE and it does, but given it's still running TOS and ST's do the same thing because there isn't any disk change detection, I'm not at all surprised by that.

Thanks for checking.
I'll just keep the drive unmodified then (except the DS1 jumper of course) as it appears to be working as intended.

As for others STs: I'm sure I've experienced that with my STe (TOS 2.06) the floppy drive won't spin a second time if I press ESC, but only does this if I eject the disk, then re-insert the same disk or another one and press ESC. I don't have the STe set up at the moment, but I'm pretty sure this is how I remember it.

It depends a lot on TOS version as to the behaviour of ESC.. But ideally should spin the motor and recheck the floppy each time ESC is pressed. Otherwise TOS may not know the floppy has changed or not.

What you say makes sense of course.
I'll have to check with the STe once I get this Mega STe fully working and set up again.

Pacman wrote: 12 Apr 2021 15:15 Thanks for checking.
I'll just keep the drive unmodified then (except the DS1 jumper of course) as it appears to be working as intended.

As for others STs: I'm sure I've experienced that with my STe (TOS 2.06) the floppy drive won't spin a second time if I press ESC, but only does this if I eject the disk, then re-insert the same disk or another one and press ESC. I don't have the STe set up at the moment, but I'm pretty sure this is how I remember it.

I think the first time after inserting a disk it is more noticeable as there is a clunk, but after that I do see the busy light come on when I hit ESC repeatedly.

My memory is that disk change detection works on the Epson drives Atari used. That's why I made sure to get Epson 340 when I wanted to HD modify my machines.

/Troed

rubber_jonnie wrote: 11 Apr 2021 15:12 Out of curiosity what revision mainboard do you have? If it's B or later then the jumper wire between the GAL (PAL) and the CPU isn't required according to the 1.44MB upgrade manual from Atari.

I desoldered the wire and checked for continuity between the same pins -there was none, so I assume my "revision 4.1" MSTE motherboard means it's earlier than "revision B" (photo of my PCB here).

On a sidenote there's a resistor connecting two pins underneath another GAL chip to be used with a 68881 co-processor upgrade and thanks to a photo on Troed's website (the first photo showing the empty co-processor PLCC socket) I noticed the excellent idea of putting it in a socket on the other side instead (meaning no need to disassemble the entire computer in case a 68881 is to be installed). Thanks Troed!
Apart from these two "solder side modifications" I don't think there's any other need to fiddle with the solder-side again.