2.88 floppy in 770? Or UltraBay to UB-II adapter, perhaps?

[NathanA]

I have an old 770 that I have an interest in fitting a 2.88MB floppy drive into, provided that it's possible.

I understand that there was no 2.88 ED floppy drive ever manufactured for the 770 series (no UltraBay II model). That said, it sounds like the UltraBay connector on the outside of an UltraBay floppy module is not wired directly to the drive's control board, but rather is adapted within the UltraBay "shell" to a different connector. Furthermore, it sounds like the floppy drives inside of UltraBay I (75x/76x) floppy modules have a connector that is physically compatible with at least some other later UltraBay series, like the UltraBay 2000...in fact, somebody on these forums tried this experiment (swapping the "guts" of a 75x/76x 2.88 floppy drive into an UltraBay 2000 floppy module) a few years ago, according to this thread over here. (He went on to say that Windows on the computers he tried his FrankenDrive in only recognized it as a 1.44MB floppy, with speculation by others following on why that might be: the BIOS? the floppy controller on the ThinkPad's motherboard? etc. & the question never was conclusively answered)

Anyway, anybody ever try this with a 770? Rip a 75x/76x 2.88 UltraBay drive's guts out & stick them in the shell of a 1.44MB UltraBay-II floppy drive?

Alternatively / tangentially-related, ThinkWiki claims that an UltraBay to UltraBay-II Adapter exists (and is not to be confused with the UltraBay II Hard Drive Adapter!), which -- if true -- would mean one wouldn't have to hack apart a 770 floppy drive to accomplish this. Since UB-II modules are physically larger than UB-I ones, it *seems* like a feasible thing that *could* exist; however, I can find ZERO reference to such a thing outside of this one page on this one web site. I can't find any past or present eBay listings, I can't find any mention of such a thing in past posts to this illustrious forum, it is not mentioned at all in the official 770/E/ED/X/Z Hardware Maintenance Manual by IBM, and even the wiki page provides no pictures nor does it list any IBM P/Ns or FRUs for such a thing. This leads me to conclude that *IF* such a thing even actually exists, it most likely was a third-party accessory and that they are scarce. ...but does anyone actually know anything about this?

Thanks much for any information or leads!

[NathanA]

Hmm. I just learned that at the very least, IBM offered an Option for your SelectaDock-III where you can swap out the single UltraBay-II slot for a 2-device UltraBay tray. From what I can tell, it looks identical to the UB tray that the SD-II would just have come with (and I'm sure it's 100% identical).

Maybe whoever threw that page up on ThinkWiki caught wind of that and was confused?

I do have a SD-III somewhere in storage, but assuming I can even find one of these UB-I trays for it, by the time I buy it + a 2.88 drive, I'm guessing I'm probably in the hole way more $$ than if I just performed surgery on a 1.44 UB-II drive...

[kfzhu1229]

The BIOS on these might stand in the way indeed.
My argument for that comes from the fact that if you stick in a DVD/CD-RW combo burner drive from an Ultrabay 2000 converted to Ultraslimbay to a ThinkPad 600, it works under Windows just fine, but under BIOS it shows up as a CD-ROM drive and has some trouble booting off DVD's.
Even worse, if you put such a drive in the external PCMCIA enclosure meant for 240 series, it won't even show up as a DVD drive in Windows nor will it work as one or even a CD-RW rewritable drive!
Is it possible for you to get around this by just using a ZIP drive?

[NathanA]

The BIOS on these might stand in the way indeed.

It's possible, but as pointed out in the other thread, it should also be possible to get an OS to ignore the BIOS and treat it as the right kind of drive regardless. Whether that's achievable with DOS/Windows specifically, I don't know yet. (Maybe with a TSR that intercepts the right BIOS calls?) I'd wager you'd have better luck with an NT-based OS or Linux.

Pretty sure that even if 2.88 support isn't in the 770's BIOS, that most floppy controllers by this point had 2.88 support...IBM would have needed to go out of their way to either source or engineer a FDC without 2.88 mode. Although I've run into hardly any PC-compatible 2.88 drives in my lifetime, the vast majority of desktop motherboards from that era that I've encountered have 2.88 as a selectable option. Most SKUs of the Intel 82077 floppy disk controller supported 2.88, and most "super I/O" chips of the era (late 90s/early aughts) that had a FDC built-in were straight-up clones of the 82077. It looks like the 770 series actually used a NatSemi PC97338, and the datasheet for that shows that it absolutely supports perpendicular record mode (2.88).

It's also interesting (though by no means conclusive) that the HMM for the 770 series specifically mentions 2.88 in its floppy drive and diskette compatibility matrix, while the HMM for machines from a later era (e.g. A3x) do not (even though the A31 had a PC87392, which also natively supports 2.88!).

My argument for that comes from the fact that if you stick in a DVD/CD-RW combo burner drive from an Ultrabay 2000 converted to Ultraslimbay to a ThinkPad 600, it works under Windows just fine, but under BIOS it shows up as a CD-ROM drive and has some trouble booting off DVD's.

Interesting. However, I can't imagine that, whatever booting-off-DVD problem you're having, that it's the fault of the BIOS. I believe that the ATAPI command-set abstracts enough low-level details about the drive away from the BIOS that, to a BIOS with ATAPI boot support, a DVD-ROM drive just looks like a CD-ROM to it but with a larger capacity (LBA count). All that the BIOS would need to do is read and execute the chain of El Torito Boot Record > Boot Catalog > Boot File all from the front of the disc, after which the OS being booted takes over direct control of the remainder of the process from there (loading IDE/ATAPI & filesystem drivers, etc.).

Even worse, if you put such a drive in the external PCMCIA enclosure meant for 240 series, it won't even show up as a DVD drive in Windows nor will it work as one or even a CD-RW rewritable drive!

Sounds to me like whatever that PCMCIA interface does, it's not merely acting as a simple ATAPI bridge. I'd guess that it (and/or its drivers) is somehow to blame, not BIOS.

Is it possible for you to get around this by just using a ZIP drive?

No. I'm not attempting this because I need removable media on the 770 that's > 1.44MB floppies. (If that was the problem I was trying to solve, I could just use the USB port!) I want to do this because I have ED floppies with data already on them that I want to be able to read, and I have no other PC currently in my possession that I could practically accomplish this with other than the 770. There is no such thing as a 2.88MB USB floppy drive, sadly. I also haven't owned a functional desktop PC (or PS/2) system in ages with floppy support, and even if I did have one, the asking prices for PC-compatible 2.88 ED drives (standard 34-pin Shugart bus interface with power carried separately over a 4-pin header) are insane. (The PS/2-compatible drives with the electrically-incompatible-with-standard-PC interface seem to be more common.)

[NathanA]

[...] it should also be possible to get an OS to ignore the BIOS and treat it as the right kind of drive regardless. Whether that's achievable with DOS/Windows specifically, I don't know yet. (Maybe with a TSR that intercepts the right BIOS calls?)

Turns out MS-DOS can already do this natively: https://web.csulb.edu/~murdock/drivparm.html

[NathanA]

So, I finally got around to trying this (after some side adventures trying to hook these older ThinkPad 75x/76x 2.88 floppy disk drives up to a desktop PC...another tale for another time), and it works! ...but it can only read HD disks, not ED disks.

*sad trombone*

I'll be trying some workarounds in the near future, though, and will update y'all if I have any success.

[pkiff]

Alternatively / tangentially-related, ThinkWiki claims that an UltraBay to UltraBay-II Adapter exists (and is not to be confused with the UltraBay II Hard Drive Adapter!), which -- if true -- would mean one wouldn't have to hack apart a 770 floppy drive to accomplish this. Since UB-II modules are physically larger than UB-I ones, it *seems* like a feasible thing that *could* exist; however, I can find ZERO reference to such a thing outside of this one page on this one web site. I can't find any past or present eBay listings, I can't find any mention of such a thing in past posts to this illustrious forum, it is not mentioned at all in the official 770/E/ED/X/Z Hardware Maintenance Manual by IBM, and even the wiki page provides no pictures nor does it list any IBM P/Ns or FRUs for such a thing. This leads me to conclude that *IF* such a thing even actually exists, it most likely was a third-party accessory and that they are scarce. ...but does anyone actually know anything about this?

I was curious to see this in the ThinkWiki as well. I don't recall seeing one, and at one time I was searching around for all kinds of obscure 770Z and UltraBay devices. But that doesn't mean it didn't exist.

Hmm. I just learned that at the very least, IBM offered an Option for your SelectaDock-III where you can swap out the single UltraBay-II slot for a 2-device UltraBay tray. From what I can tell, it looks identical to the UB tray that the SD-II would just have come with (and I'm sure it's 100% identical).

Now this is something I actually know a bit about. I used this thing at one point in my SelectaDock III. I had a Thinkpad 760 and thought that it might be handy to have a tray available for those devices. And I had also hoped that it would allow me to add two hard drives into the single bay instead of just one. But if I recall, I couldn't actually get it to work very well for some reason - maybe it didn't allow two hard drives simultaneously? Or maybe I was annoyed that you had to open up the dock in order to swap things in and out (they didn't just slip in and out like the Ultrabay II devices do). I forget some of the details. But in the end, I found the best setup for me was to install a standard device in one bay of the SelectaDock III and then use the Ultrabay II slot for my various 770 devices, and skip trying to connect any of my 760 devices.

I'm pretty sure that you wouldn't be able to use this 2-device UltraBay tray for any kind of floppy because the bay is totally enclosed. They fit sideways in the slot(?) [Later: I see in the link you added that according to the spec, it will fit a floppy+HDD or CD+HDD, so maybe my recollection of how it worked is totally wrong!]. Even if you could cut away at the hardware, they floppy would be facing the wrong direction instead of facing out towards the front of the SelectaDock. I may even have this device boxed up somewhere after I pulled it out. Though I probably wouldn't let it go for sale as it's the kind of weird add-on that I like to hold onto for obscure, totally impractical, irrational reasons.

[pkiff]

Just found the "Thinkpad 760 Ultrabay Options Tray for Selectadock III" in my basement. It looks like it does actually do what you want: allows you to install a standard Ultrabay floppy drive into the Ultrabay II slot of the SelectaDock III. The boxed version comes with a choice of different front bezels. The bezel I remembered is a blank for hard drives, which are indeed placed sideways. But it also comes with a bezel to use when you install a floppy and another for use with an Ultrabay CD.

I might poke around this week and see if I have another one sitting around that I might share.

[NathanA]

Just found the "Thinkpad 760 Ultrabay Options Tray for Selectadock III" in my basement. It looks like it does actually do what you want: allows you to install a standard Ultrabay floppy drive into the Ultrabay II slot of the SelectaDock III. The boxed version comes with a choice of different front bezels. The bezel I remembered is a blank for hard drives, which are indeed placed sideways. But it also comes with a bezel to use when you install a floppy and another for use with an Ultrabay CD.

Yeah, I was pretty sure I was reading the HMM correctly and that this was possible with this option. I'm also fairly sure that if you have a SD-II, the bay from that is exactly the same part that is shipped as that Option, so if you have a SD-II, you can just remove the UB-I tray from it and install it into your SD-III in place of the UB-II one.

I might poke around this week and see if I have another one sitting around that I might share.

That is quite kind of you to even take time to check, though at this stage I don't think I strictly need it: if you see my last post, I have built a seemingly-working "2.88 UB-II floppy drive" out of a 1.44 UB-II floppy drive and a 75x 2.88 drive. It just doesn't work with 2.88 media (at least not yet). And I doubt that putting the drive in the SelectaDock is going to change that...

Though I probably wouldn't let it go for sale as it's the kind of weird add-on that I like to hold onto for obscure, totally impractical, irrational reasons.

Hahahaha I am TOTALLY the same way. You never know when you might need to use it again. Heck, I didn't foresee myself trying to get a 2.88 MB drive working in 2021, but here we are. If I were in your shoes, I'd keep it, too. Would save me the trouble of having to try to hunt another one down again later if I ever needed it again.

In fact, the crazy part of this story is that many, many years ago, I bought two SelectaDocks from eBay: one turned out to be a SD-II and the other a III. I don't remember the exact details lo these many years later, but though they were both used, I think both were also pretty much parts-complete. The II turned out to be defective somehow, and since these are very big docks that are heavy and take up a lot of space, I am pretty sure I dumped the seemingly-not-working II and only kept the III. Very very very stupid mistake on my part in retrospect, esp. since now I realize that I could have harvested the UB tray from the II to be used in the III.

...and now I cannot even seem to locate my III. *sigh* Given how big it is, you'd think it would be hard to hide.

[NathanA]

Just a quick note that I managed to get the 2.88 drive reading and writing 2.88 disks in my 770.

In the end, it appears to have been a BIOS issue. As far as I can tell, either the 770 BIOS plain doesn't support 2.88 drives, or there is support lurking in the BIOS code but no way to enable it (no user-facing method of twiddling the right bit inside of CMOS to indicate that it's a 2.88 drive).

I found a little DOS TSR that's part of the "2M" disk formatting program called 2M-ABIOS. It is a substitute for the BIOS disk routines, and when it's loaded, it hooks into software interrupt 13h, which is normally what DOS would call in order to utilize the BIOS routines. Putting this "driver" on a DOS installation and adding it to CONFIG.SYS with the appropriate parameters indicating that a 2.88 drive lives at A: got 2.88 support on this drive working. I suspect there may be similar ways of forcing the issue on other OSes (on Linux, perhaps a kernel command line parameter, and on Windows versions that actually have 2.88 support, perhaps some mucking around in Device Manager or the Registery), but this worked for what I needed to accomplish.

Before trying 2M-ABIOS, I had tried DOS's native DRIVPARM & DRIVER.SYS options, but neither worked (even when trying with the /I parameter passed to DRIVPARM).

Before I managed to get this working, I wondered whether the 770 might at least support a 2.88 drive & media directly as long as the drive was housed in a SelectaDock with the UltraBay tray installed. I suppose it's still possible that it might, but at the moment the question is merely academic for me.

[pkiff]

Great news! Thanks for the update and details.