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SE/30 two floppy cable mod
- Thread starter daveosx
- Start date
BadGoldEagle
Well-known member
I have never seen a dual floppy setup on an SE/30. I thought it was impossible because there's only one floppy port. The SE could be optioned with a second FDD, but the SE logic board has two connectors. I mean you could hack the external connector but...
Anyway, I'm afraid I can't help you with that mod. But I'd love to see the result! Which bezel will you be using? SE or modded SE/30?
Anyway, I'm afraid I can't help you with that mod. But I'd love to see the result! Which bezel will you be using? SE or modded SE/30?
BadGoldEagle
Well-known member
You may find this interesting though: http://www.hardwarebook.info/Apple_Macintosh_Internal_Floppy_disk_drive
bigmessowires
Well-known member
I'm pretty sure that's not possible, unless you're considering rewiring the external floppy connector to be internal somehow. Like BadGoldEagle said, you may be thinking of the SE (not SE/30).
Well it's an interesting question. If they both use the same SWIM chip, and there isn't some other component involved (VIAs perhaps) then, in theory, shouldn't all the resources that allow an SE to distinguish between three different floppies also be present in the SE/30 even if an ID pin or some such is not brought to the floppy cable socket? I suppose that the SE/30 might also lack firmware support for three floppies, but Apple seems to have been pretty general about that.
So what mechanism does the machine use to distinguish between the floppy drives? Something akin to a Chip Enable line? Or something completely different?
So what mechanism does the machine use to distinguish between the floppy drives? Something akin to a Chip Enable line? Or something completely different?
techknight
Well-known member
I am fairly certain the VIA is used as the drive select. Or it might even be the GLU.
I know the MISC GLU in the macintosh portable contains the drive select for the FDD units.
I know the MISC GLU in the macintosh portable contains the drive select for the FDD units.
bigmessowires
Well-known member
There's an enable pin on each disk connector, which is used to independently select one of the available floppy drives. On the 20-pin internal connector, it's pin 14. This is the only pin that's unique for each drive, and all the other pins are shared between all drives.
On most Macs, there's the potential for two floppy drives, and the two separate enable signals are both generated by the IWM or SWIM chip. On the SE, the necessary third enable signal is generated by some other chip - the VIA maybe?
The Sony floppy driver in the Mac's ROM needs to know how many floppy drives are possible, and what chips to activate in what way to enable each one. It seems very doubtful the SE/30 ROM would have support for activating some extra chip to enable a 3rd floppy drive, since that Mac model never had a 3rd floppy drive. In theory you could write your replacement floppy driver that supports 3 drives, hijack an unused output from some other chip to use as a 3rd enable signal, and solder in some patch wires to make it work. But that seems a little bit insane.
On most Macs, there's the potential for two floppy drives, and the two separate enable signals are both generated by the IWM or SWIM chip. On the SE, the necessary third enable signal is generated by some other chip - the VIA maybe?
The Sony floppy driver in the Mac's ROM needs to know how many floppy drives are possible, and what chips to activate in what way to enable each one. It seems very doubtful the SE/30 ROM would have support for activating some extra chip to enable a 3rd floppy drive, since that Mac model never had a 3rd floppy drive. In theory you could write your replacement floppy driver that supports 3 drives, hijack an unused output from some other chip to use as a 3rd enable signal, and solder in some patch wires to make it work. But that seems a little bit insane.
techknight
Well-known member
Yea, especially for a floppy drive...
daveosx
Member
Ok so what I am understanding is that there is a signal on internal pin 14 from the drive to the controller.
I do believe that the se/30 can use more than one external floppy drive in a daisy chain config.
I will give it a try on the external first and sort out how by looking at the external drive wiring.
I need to fix the eject gears on my externals I just got the batch of 8 I needed and have resurrected three of my drives so far.
Over the weekend I should be able to figure it out.
I will look closely at the pin 14 routing in the external cases and see if thats the trick.
I will try and do a write up.
Now that we have the scsi2sd it allows plenty of room for mounting on top of the second floppy bracket.
I have a clear case Se that is upgraded to a se30 moved my Seagate 8gig to a mac bottom enclosure and the empty slot is bugging me.
I do believe that the se/30 can use more than one external floppy drive in a daisy chain config.
I will give it a try on the external first and sort out how by looking at the external drive wiring.
I need to fix the eject gears on my externals I just got the batch of 8 I needed and have resurrected three of my drives so far.
Over the weekend I should be able to figure it out.
I will look closely at the pin 14 routing in the external cases and see if thats the trick.
I will try and do a write up.
Now that we have the scsi2sd it allows plenty of room for mounting on top of the second floppy bracket.
I have a clear case Se that is upgraded to a se30 moved my Seagate 8gig to a mac bottom enclosure and the empty slot is bugging me.
Scott Baret
Well-known member
I'm interested to see how this turns out. I know some Macs do technically have the capability on-board (I'm pretty sure the LCII does if you add the right connector).
bigmessowires
Well-known member
Unfortunately that's not true. The only thing like a daisy-chain that's possible on a Macintosh is an HD20 hard disk connected to a floppy disk. But that requires extra smarts in the HD20 to know when to react to signals itself and when to pass them through to the floppy drive. And even then, you can still only have one internal and one external floppy drive. This also requires HD20 support in ROM, which the SE/30 lacks.
Sorry to be a wet blanket, but I just don't think three simultaneous floppies are possible on the SE/30, short of a truly heroic effort involving a custom ROM and logic board modifications.
Scott Baret
Well-known member
As I recall, the daisy chain floppy drives only work on the Apple II computers.
The only classic Mac capable of driving three floppies at a time is the SE (not SE/30) when equipped with two floppies and an external drive. Still, the system accounts for a third floppy drive (it even has a keyboard shortcut, Shift-Command-Zero, to eject from a third floppy, built in).
I wonder if the fabled DuoDisk 3.5" would work on a Mac, with only one drive active?
The only classic Mac capable of driving three floppies at a time is the SE (not SE/30) when equipped with two floppies and an external drive. Still, the system accounts for a third floppy drive (it even has a keyboard shortcut, Shift-Command-Zero, to eject from a third floppy, built in).
I wonder if the fabled DuoDisk 3.5" would work on a Mac, with only one drive active?
BadGoldEagle
Well-known member
Well, I've seen pictures on the net of a prototype twin 800k external floppy drive for the IIGS. One was sold on eBay for a considerable sum: $933 !!
(Just saved the eBay listing on the web archive. Might be useful to someone in the future...?)
Unfortunately this is a non-working drive... And it is for the Apple IIGS only. Standard Apple II UniDisk (A2M2053) won't work on any Macintoshes. As Scott said above, daisy chain floppy drives only work on Apple II computers.
If you really need an 030 and dual floppies, then you could get one of those Radius Accelerators for the Mac SE. I know some of them can address more than 8meg of RAM, support FPUs and are 32-bit clean. But you'll have to give up the whole color quickdraw thing. You don't need it that much if you don't have a color card installed anyway...
Some versions of mini vMac will let you add floppy drives infinitely. I don't know why, though... Mac Plus ROM or custom software??
That lead needs investigating. Maybe it's possible to hack the SE/30 ROM (using BMOW's ROMinator II)?
Edit:
Scott Baret, on 24 Jun 2016 - 08:10 AM, said:
I wonder if the fabled DuoDisk 3.5" would work on a Mac, with only one drive active?
-> I don't think so unfortunately as it needs to be hacked in order to be used on a IIGS, so chances are, it will never work on the Mac...
(Just saved the eBay listing on the web archive. Might be useful to someone in the future...?)
Unfortunately this is a non-working drive... And it is for the Apple IIGS only. Standard Apple II UniDisk (A2M2053) won't work on any Macintoshes. As Scott said above, daisy chain floppy drives only work on Apple II computers.
If you really need an 030 and dual floppies, then you could get one of those Radius Accelerators for the Mac SE. I know some of them can address more than 8meg of RAM, support FPUs and are 32-bit clean. But you'll have to give up the whole color quickdraw thing. You don't need it that much if you don't have a color card installed anyway...
Some versions of mini vMac will let you add floppy drives infinitely. I don't know why, though... Mac Plus ROM or custom software??
That lead needs investigating. Maybe it's possible to hack the SE/30 ROM (using BMOW's ROMinator II)?
Edit:
Scott Baret, on 24 Jun 2016 - 08:10 AM, said:
I wonder if the fabled DuoDisk 3.5" would work on a Mac, with only one drive active?
-> I don't think so unfortunately as it needs to be hacked in order to be used on a IIGS, so chances are, it will never work on the Mac...
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bigmessowires
Well-known member
Mini vMac doesn't actually emulate floppies it all. It bypasses all of it, and just makes direct calls to the host Windows/OSX operating system whenever the emulated computer wants to do file I/O. Which is pretty darn convenient, but not at all realistic for real hardware.
Two daisy-chained 3.5 inch drives are no problem on an Apple II system like a IIGS or IIc+, but that's because the drives are controlled using a different method than for the Macintosh family. If you like building custom stuff, I think it wouldn't be too hard to take the guts of two 3.5 inch drives and put them inside a new case, with an internal daisy chain connection between them. Then you'd basically have something like the Apple II twin 800k external floppy drive that you mentioned.
Last edited by a moderator:
daveosx
Member
Ok todays quick look at the external drive shows an extra board IF-89 Sony 1-619-250-14 with a chip cxd10858 on the bottom.
I see enb2 for the incoming cable enb1 for the inside drive and enb3 for the db19 out.
looks like enb3 passes through from pin 7 to pin three and external and enb2 passes to pin 14 of the drive ribbon.
I do not know where I left the tray bottom and cable when the eject failed years ago.
I am fixing the drive and will reassemble it soon as I can locate the bottom cable and tray.
I will give it a try with three devices on my Se30 see what happens.
I know that many years ago I had two of these connected to this mac at the same time.
I do not remember if all three worked.
If someone could check theirs it would satisfy my curiosity.
I have tried crazier things that worked undocumented in the past.
Either way it was not what I was really thinking of I kind of just want to make use of the empty slot in the front now that I have room.
I was also thinking today of just moving the scsi2sd farther forward on the tray to allow swapping the sd cards from the front open slot.
I see enb2 for the incoming cable enb1 for the inside drive and enb3 for the db19 out.
looks like enb3 passes through from pin 7 to pin three and external and enb2 passes to pin 14 of the drive ribbon.
I do not know where I left the tray bottom and cable when the eject failed years ago.
I am fixing the drive and will reassemble it soon as I can locate the bottom cable and tray.
I will give it a try with three devices on my Se30 see what happens.
I know that many years ago I had two of these connected to this mac at the same time.
I do not remember if all three worked.
If someone could check theirs it would satisfy my curiosity.
I have tried crazier things that worked undocumented in the past.
Either way it was not what I was really thinking of I kind of just want to make use of the empty slot in the front now that I have room.
I was also thinking today of just moving the scsi2sd farther forward on the tray to allow swapping the sd cards from the front open slot.
bigmessowires
Well-known member
There's extensive discussion about this interface on my site if you are curious, including schematics for that chip. The mac's external db19 has no physical connection for the extra drive enable signal - it's for apple ii only.
daveosx
Member
Thanks
Could you provide links to the discussion ?
You are the GURU of the floppy for sure.
I have another post here about the LUN issue with scsi on the mac.
This also seems implementable.
Just seams like there could be a way considering the original HD20 used the DB19 for a HDD with the init.
I am thinking it could be implemented by using the phase control lines to signal a gate or maybe even specific read and write commands.
I need to read more about how the floppies actually work and see if there is any unused states that could be redirected.
but that is another whole project.
bigmessowires
Well-known member
This post has a schematic of that Sony chip: http://www.bigmessowires.com/2015/03/25/apple-ii-emulation-forever/Most of the following posts from the next few months of the blog have related info. The series of posts starting around February 2015 also have more details about the HD20 communication protocol.
It's definitely possible, just for very high values of possible. Your original post sounded like you were looking for a simple cable modification or something easy, and I don't think any simple three-drive solution exists for the SE/30. If you're willing to try writing your own floppy drivers and adding some new external hardware to decode the I/O lines into extra control signals, you could invent anything you can dream of (at 150 kbps anyway). That's essentially how the HD20 works.
If your main concern is just to plug the empty drive bay, how about adding a 3rd floppy drive that's wired in parallel with the external drive connector, with a physical switch to select which drive is active at any given time? That would give you 3 floppy drives, though you could only use 2 of them at a time. There's a disk drive A/B switch on my web site that basically does this already - check the site for the schematics. Or just re-route your external floppy drive connector to a second internal drive, if you don't plan to use the external connector for anything else.
It's definitely possible, just for very high values of possible.
Your original post sounded like you were looking for a simple cable modification or something easy, and I don't think any simple three-drive solution exists for the SE/30. If you're willing to try writing your own floppy drivers and adding some new external hardware to decode the I/O lines into extra control signals, you could invent anything you can dream of (at 150 kbps anyway). That's essentially how the HD20 works.If your main concern is just to plug the empty drive bay, how about adding a 3rd floppy drive that's wired in parallel with the external drive connector, with a physical switch to select which drive is active at any given time? That would give you 3 floppy drives, though you could only use 2 of them at a time. There's a disk drive A/B switch on my web site that basically does this already - check the site for the schematics. Or just re-route your external floppy drive connector to a second internal drive, if you don't plan to use the external connector for anything else.
