Anyone have a Powerbook 100 and a Floppy Emu?

[Tashtari]

It's time for another Tashtari shenanigan. (You don't see that word used in the singular very often, do you...)

So here's the situation: I'm about 99.9% sure that the Powerbook 100 has HD20/DCD support in ROM, but I want to be 100% sure.

As with all machines with HD20/DCD support, the device has to be connected to the second drive enable line in order to be detected by the Mac (all other disk drive lines are common between the primary and secondary drive). On the PB100, I believe that the second drive enable is connected to the HDI-20 port used to hook up the external floppy drive, it's just that nobody has made a cable that can be used to connect this to a Floppy Emu or a TashTwenty in order to test this.

...Until now.





I bought a nonworking (at least I hope it was) PB100 external floppy drive off ebay and found that the cable was fortuitously connected to a 2x10 header rather than hardwired, and with a little searching, I was able to procure the mating connector and spin a PCB to act as an adapter.

There's just one little problem - I don't own a PB100.

I am seeking a volunteer from the audience who owns a working PB100 and a Floppy Emu (or a TashTwenty product such as demik's TashTwenty Tiny that has a 2x10 header for connection) to hook it up and see whether HD20 support really exists in the PB100's ROM. I'll ship you the cable and adapter PCB at my own expense.

What's in it for you? Well... you get to keep the cable and adapter PCB (I certainly don't need it back for anything), you get your name forever enshrined in a document on Github, and you get the satisfaction of having advanced the cause of Science!

Any takers?

 

[Franklinstein]

I can probably help out eventually but I'd have to see if my PB100 is still alive. Also I'd have to get a FloppyEmu (which I probably should anyway). Is there a particular revision/variant that would work best for this?

 

[David Cook]

Yes, I have both in working condition and would be happy to test it.. Sending a PM.

 

[Chuckdubuque]

If you get it to work it should also be good for PowerBook Duos which used the same floppy interface.

 

[Tashtari]

Volunteer get! Thanks @David Cook !

If you get it to work it should also be good for PowerBook Duos which used the same floppy interface.

Unfortunately the limiting factor here is the ROM rather than the interface - to my knowledge, no other Powerbooks have HD20 support in ROM - though the cable would still be good for connecting a Floppy Emu as a floppy drive.


If anyone else is interested in this (or becomes interested in it after it's proven), I've got four more copies of the adapter PCB and I ordered connectors for them as well because I am pathologically incapable of ordering anything in a quantity of one from Digikey. Message me and I'd be happy to send them to you at cost.

 

[Tashtari]

Mostly for future reference, I've uploaded the board file and Gerbers for this board to a new repo on my Github here (among some others):

GitHub - lampmerchant/misc-mac-pcbs: Miscellaneous PCBs for Macintosh retrocomputing.

Miscellaneous PCBs for Macintosh retrocomputing. Contribute to lampmerchant/misc-mac-pcbs development by creating an account on GitHub.

github.com

 

[Realitystorm]

So here's the situation: I'm about 99.9% sure that the Powerbook 100 has HD20/DCD support in ROM, but I want to be 100% sure.

The Macintosh portable does, but no mention of the PowerBook 100 https://savagetaylor.com/TIL/TA40360.html, and https://www.savagetaylor.com/TIL/TA44724.html

 

[David Cook]

 

[David Cook]

Despite what is written in Apple's PowerBook 100 developer note, other sites indicate that the PowerBook 100's ROM is a newer revision than the Portable.

 

[Tashtari]

My 99.9-percent-sureness comes from the fact that the .Sony driver in the PB100's ROM is the same size as the one in the Portable's ROM (and some others, I think, it's been a long time). But we won't know 'til we know.

 

[Tashtari]

The Macintosh portable does, but no mention of the PowerBook 100 https://savagetaylor.com/TIL/TA40360.html, and https://www.savagetaylor.com/TIL/TA44724.html

That first link is incorrect, the LC and IIsi are known to have HD20 support in ROM. BMOW's compatibility list is better, but it leaves out a few more models (the LC II, IIvi, and IIvx) that have been tested and proven to have support in ROM - my list is the most complete and correct, to my knowledge - the PB100 is the biggest question mark there.

 

[Tashtari]

@David Cook - glad to see that there's an Apple source that confirms that pins 6-9 are +5V, that was my biggest worry in spinning the PCB because it's the biggest difference between the HDI-20 pinout and the standard drive connector pinout...

That first link is incorrect, the LC and IIsi are known to have HD20 support in ROM.

It's understandable that they say the LC doesn't have support as the LC doesn't have an external floppy drive connector (you have to use the secondary internal drive header), but the IIsi does, I don't know why they say it doesn't have support.

 

[Realitystorm]

That first link is incorrect, the LC and IIsi are known to have HD20 support in ROM.

Interesting, another example of Apple's TIL articles about their own hardware being wrong.

 

[cheesestraws]

I don't know why they say it doesn't have support.

Interesting, another example of Apple's TIL articles about their own hardware being wrong.

I suspect what we're hitting here is the distinction between 'It works' and 'If someone phones up looking for tech support for this configuration, we will offer them useful advice'

 

[David Cook]

Okay. I just received it. I hope you don't mind us walking through the development process in the open forum (as opposed to direct messages).

The connector on your adapter board is female, but unfortunately, so is the ribbon cable on the Floppy EMU.

So, I figured I would just pull the ribbon cable on the Floppy EMU and directly connect your adapter board after opening the Floppy EMU case. Unfortunately, the keyed direction of the board is such that it is blocked by the Floppy EMU screen.



My next step is to desolder the female connector and replace it with a male. Any concerns before I do so?

 

[David Cook]

Congratulations @Tashtari it works! You were right about the PowerBook 100 having native HD20 support in ROM. It can even boot off the HD20 (being emulated by @bigmessowires Floppy Emu).



Swap the female connector for a male and you've got yourself an adapter.

I used some header pins temporarily.



- David

 

[Tashtari]

Unfortunately, the keyed direction of the board is such that it is blocked by the Floppy EMU screen.

D'oh, I'm a bonehead, I thought I checked that...

Congratulations @Tashtari it works! You were right about the PowerBook 100 having native HD20 support in ROM. It can even boot off the HD20 (being emulated by @bigmessowires Floppy Emu).

Victory! I'm so glad to have it experimentally confirmed, I've updated the compatibility page in TashNotes. Thanks again for doing this!

 

[Tashtari]

Okay, I've made a new spin of the board that swaps the positions of the two connectors, should have done that to begin with. It's available in my misc-mac-pcbs repo on Github.

 

[Realitystorm]

I update the html version of the TIL document to show your findings, and direct people to this discussion and your GitHub. I'm going to try to do the same for other articles if we find they are incomplete or incorrect. The PDF versions will be a pain though.

 

[Tashtari]

To everyone I sent adapters to, I included some of the new PCBs in my latest JLCPCB order, so if you can stand to wait a couple weeks for them to arrive, I'll be happy to send you replacement PCBs when they come in. Should be pretty cheap, I can probably just send them in a standard envelope instead of a box...

I update the html version of the TIL document to show your findings, and direct people to this discussion and your GitHub. I'm going to try to do the same for other articles if we find they are incomplete or incorrect. The PDF versions will be a pain though.

Sounds like a heavy lift but good on you for setting the record straight!