Anyone have a IIvx (or IIvi) and a Floppy Emu?

[tashtari]

...And want to advance the cause of Science?

So, here's the thing. It's already been well established by Floppy Emu users what Macs with secondary floppy connectors (whether internal or external) that support the HD20 and DCD emulators like the Floppy Emu and my own TashTwenty. What still remains mysterious is what Macs without a secondary floppy connector support it.

Background: All the signals on the Mac floppy interface are shared between all drives in the system except for the drive-enable line. The IWM and SWIM have exactly two of these. The HD20 plugs into the floppy interface, but every Mac ROM known to support the HD20 will only recognize it if it's connected to the secondary drive-enable line, !ENBL2. Even if it's not routed anywhere on the logic board, the SWIM chip always has an !ENBL2 signal, and it can be accessed by clipping onto the appropriate leg of the PLCC (or soldering a wire there). I've found experimentally that the LC II supports the HD20, and now I'm wondering what other machines fall into the same category.

I wrote some code to take each of the ROM images in my collection and extract the .Sony driver. Only a few were exactly identical (the LC and LC II, and the Q610 and Q650) but several had the same size. In the 18K group were the LC, the LC II, the Classic II, and the IIsi, all machines that are known to support the HD20... also in that group was the IIvx, a machine that is not known to support the HD20. I'm wondering whether it secretly can.

This is a long shot, but what I'm hoping for is a brave soul who is willing to open their IIvx (or IIvi as they're nearly identical and probably have very similar or identical ROMs) and connect a Floppy Emu in HD20 emulation mode such that all the signals from the internal floppy connector are routed to the Floppy Emu except the !ENBL signal on pin 14, and use an IC pin clip (or solder, if you're daring) to connect that pin to the !ENBL2 pin on the SWIM (pin 19) and see if the emulated HD20 drive comes up.

Anyone? For Science? Bueller? Bueller? =)

 

[mg.man]

Hmm... maybe. I say maybe mainly because I'm pretty Mac-time poor atm. What I *do* have is a IIvi(x?) 'board that I pulled out to put a Q700 'board in its place. So... if I can carve out some Mac-time, I should be able to have a go. This may be another week or more, so if anyone else is able to have a go - please do!

 

[Fizzbinn]

I have a IIvx and a Floppy EMU… can you expand on the !ENBL switch-a-roo? Would I need to pull a wire out of the ribbon cable to reroute to the SWIM chip pin?

 

[tashtari]

I have a IIvx and a Floppy EMU… can you expand on the !ENBL switch-a-roo? Would I need to pull a while out of the ribbon cable to reroute to the SWIM chip pin?

Cool! So pulling a wire out of the ribbon cable is one way to do it, though of course it leaves you with an otherwise useless ribbon cable (unless this works and you decide you want to be able to do it again!) The way I did it was by using a bunch of female-to-female wire jumpers like these and just connecting the !ENBL line to the clip I hooked on the SWIM pin instead of to the floppy connector on the logic board.

 

[Fizzbinn]

Cool! So pulling a wire out of the ribbon cable is one way to do it, though of course it leaves you with an otherwise useless ribbon cable (unless this works and you decide you want to be able to do it again!) The way I did it was by using a bunch of female-to-female wire jumpers like these and just connecting the !ENBL line to the clip I hooked on the SWIM pin instead of to the floppy connector on the logic board.

Oh, I actually have some of those jumpers, that would work!

In any case I have only used my Floppy EMU with my IIgs so far so I found out I had to change the firmware to work with a Mac. I downloaded the files and used my original LC to test out/base line that the HD20 image works on a Mac for me, and it worked just fine with the Floppy EMU connected to the secondary internal floppy port (near the physical HD, left side position, !ENBL2) on my LC.

Looking over the above posts I'm thinking it might not work if connected to the primary internal floppy port (near the right side floppy drive position, !ENBL) on my LC? Will test that tomorrow. The question being if the HD20 Floppy EMU was connected to the IIvx internal floppy port (near the right side floppy drive position, !ENBL) it also would not work, but if the !ENBL2 line was used, patched in, it would?

 

[tashtari]

Looking over the above posts I'm thinking it might not work if connected to the primary internal floppy port (near the right side floppy drive position, !ENBL) on my LC? The question being if the HD20 Floppy EMU was connected to the IIvx internal floppy port (near the right side floppy drive position, !ENBL) it also would not work, but if the !ENBL2 line was used it would?

Exactly this. The only difference between the primary and secondary floppy connectors is how the !ENBL line is connected, all the other lines are common between them. Apple reasoned that the HD20 would only ever be connected to the external floppy connector, which (when it exists on a given Mac) is always connected to the !ENBL2 pin on the SWIM/IWM, that's why the ROM driver only responds when the HD20 is on !ENBL2.

 

[tashtari]

According to a collection of ROM images I found on Mac Garden, the IIvi and IIvx use the same ROM, which means if we prove one, we prove the other, that's good. (I also found that the PB100 and Portable have identical .Sony drivers, which means that the PB100 supports the HD20 too, though how you'd connect it I don't know...)

 

[mg.man]

every Mac ROM known to support the HD20 will only recognize it if it's connected to the secondary drive-enable line

Just a quick one... I haven't pulled out my IIvx, but the above got me wondering. I have an early LC with twin (physical) floppy connectors. Do you think plugging the FloppyEMU in HD20 mode into the 2nd floppy port 'will just work'?

 

[tashtari]

Do you think plugging the FloppyEMU in HD20 mode into the 2nd floppy port 'will just work'?

It will, I'm sure of it. The support is there in ROM and the secondary floppy port has !ENBL2.

 

[mg.man]

It will, I'm sure of it.

Well I guess I'll have to have a go and report back...

 

[mg.man]

How 'bout that...



I guess I need to drag out my IIvx 'board now...

 

[tashtari]

It's nice when the magic works, isn't it?

I guess I need to drag out my IIvx 'board now...

Fingers crossed!

 

[mg.man]

It's nice when the magic works, isn't it?

The annoying part is I tried my FE on my LC, but not on the 2nd floppy port. Oh well - good to know this works.

 

[tashtari]

I tried my FE on my LC, but not on the 2nd floppy port.

BMOW could stand to make this a touch clearer in the docs, they have a footnote for the LC and the IIx that says "uses internal disk connector on motherboard" but they don't specify it has to be the secondary connector.

 

[CC_333]

BMOW could stand to make this a touch clearer in the docs, they have a footnote for the LC and the IIx that says "uses internal disk connector on motherboard" but they don't specify it has to be the secondary connector.

I don't think it was known that it was necessary to use the secondary connector when BMOW first wrote the docs, was it? I was following BMOW's progress when he first invented the Floppy Emu back in... gosh, 2013 or so?... so I might be forgetting something....

I think I also have a IIvx, but nowhere to set it up for this experiment.

I'll watch and see what happens. Maybe a cleaner way of doing this !ENBL swap will be found that doesn't require messing around with the connector or clipping wires to IC pins.

Also, I don't know how viable this is, but what about somehow modifying the .sony ROM driver to listen for the HD20 on !ENBL1? If I correctly understand how this works, that could interfere with the internal floppy drive, but if it does, maybe it won't matter since the Emu in HD20 mode is so much more useful than a questionable 25+ year old floppy?

c

 

[tashtari]

I don't think it was known that it was necessary to use the secondary connector when BMOW first wrote the docs, was it?

That I don't know, but surely they know by now. Maybe I should comment on the page and bug them to update the docs.

Maybe a cleaner way of doing this !ENBL swap will be found that doesn't require messing around with the connector or clipping wires to IC pins.

That'd certainly be nice. I was going to say that I doubted that the pin was actually connected to anything on the motherboard, but I checked @max1zzz 's scan of the LC II board (another machine that has secret support for the HD20) and it actually looks like the !ENBL2 pin on the SWIM pin does go somewhere. I can't tell where, though, but perhaps when he puts the files on GitHub we can find out more... or perhaps sooner if he sees this thread and feels like taking a looksee. =)

Anyway, if the LC II routes it somewhere accessible, perhaps the IIvx does too, though I doubt anyone's going to be in much of a rush to RE the IIvx's logic board.

what about somehow modifying the .sony ROM driver to listen for the HD20 on !ENBL1

Also a possibility, though it's well beyond my skills to do it...

 

[CC_333]

That I don't know, but surely they know by now. Maybe I should comment on the page and bug them to update the docs.

That's probably a good idea, as obsolete/ambiguous information such as that could probably be very confusing for beginners.

That'd certainly be nice. I was going to say that I doubted that the pin was actually connected to anything on the motherboard, but I checked @max1zzz 's scan of the LC II board (another machine that has secret support for the HD20) and it actually looks like the !ENBL2 pin on the SWIM pin does go somewhere

That's neat! It might be tied to ground because it's not officially implemented, but this is unknowable until @max1zzz chimes in.

If it is grounded, maybe it can be broken out to a jumper instead, such that maybe with the jumper, the pin on the internal connector that's normally used for !ENBL1 can optionally be used for !ENBL2 instead?

Anyway, if the LC II routes it somewhere accessible, perhaps the IIvx does too, though I doubt anyone's going to be in much of a rush to RE the IIvx's logic board.

Perhaps, but I agree that it's not terribly likely that anyone will want to go to the trouble of reverse engineering a IIvx, although it actually has respectable specs (save for a 16MHz bus that made it roughly equivalent to a IIci, speed-wise), so maybe someone will? It got it's reputation not because it's a bad computer, but rather it was rendered obsolete almost immediately after release (the Performa 650 was released 4 months later for $250 less), and people who bought it in that period felt ripped off. That happened to me when I got my Early 2008 Mac Pro. The Early 2009 model came out less than two months after I bought it, and it was easily twice as powerful for $200 less, so I can say I got "IIvx-ed"

Also a possibility, though it's well beyond my skills to do it...

There are plenty of people around here who do have those skills. Maybe one or more of them have some thoughts/ideas on this?

c

 

[Skate323k137]

He's really responsive to email as well if you don't want to leave public comment.

My favorite new FloppyEMU Magic is that the RevC can act as two 5.25 drives at once on Apple II now. One device, two disk images... magic.

 

[max1zzz]

but I checked @max1zzz 's scan of the LC II board (another machine that has secret support for the HD20) and it actually looks like the !ENBL2 pin on the SWIM pin does go somewhere.

Unfortunately not, on the LCII the !ENBL2 (Pin 19) goes nowhere:


Though you could just tack a wire on there

but perhaps when he puts the files on GitHub we can find out more...

Been meaning to do it for ages, other projects just keep getting in my way!

 

[max1zzz]

I doubt anyone's going to be in much of a rush to RE the IIvx's logic board.

I have a IIvi board here, I have looked ar REing it but I think it is a 6 layer board which I don't have experience with (yet - the LC 475 is on my list and that's a 6 layer board)