External 5.25" drive for PS/2

[carlos12]

Hi, everyone! I just bought, quite cheap on my local market (no $Ebay$, thank God...) a CMS 360-U case for 5.25" floppy drive. I had a spare drive so I've connected into the case. It has no power cord, just a db25 female socket. So my question is: what do I need to make it work on a PS/2 model 30 8086? My guess is I need a db25 male-male cable to connect it to the parallel port. I read somewhere that some parallel ports can give power, up to 5v. Is this correct? Maybe a DOS driver would be needed? (I hope not...) I ordered the cable but still hasn't arrived. Do you think it will work just this way or will I need an ISA card for connecting external drives?

Thanks for your help!

 

[vwestlife]

A previous thread about it, unfortunately without any conclusion about what kind of interface it was meant to connect to:

https://www.vcfed.org/forum/forum/t...age-computer-hardware/3235-cms-external-drive

 

[Chuck(G)]

I must've let the old thread slip by. First of all, is the connector a DB25 or is it a DC37 (count the pins)?

 

[krebizfan]

If this drives matches other such drives, the case should be easy to open. A quick examination of the cabling between the floppy drive and the external connector should clear up how the system works. A parallel port drive needs a logic board. Straight wiring indicates the drive needs to be hooked up to the floppy controller which would require an ISA board with the model 30.

Frustratingly, I remember there was a long PC Magazine article looking at a number of PS/2 external floppy solutions but I can't come up the right issue in searches. I had hoped that it would have included a picture of the complete CMS setup and clear up the questions.

 

[carlos12]

Thank you for your responses. I think I'd may be lucky... The case has what looks like a controller (hopefully the logic board) attached to the socket, so it may work with the parallel port without needing a card. The socket is a db25.

 

[Unknown_K]

I have a 5.25" IBM drive that came with an ISA card connected to my PS/2 model 30 286 I believe (removed it when I got it and it has been a while).

Type 4869
37 pin cable (2 rows)
Built in PS
Star on the 5.25" drive faceplate.

 

[Chuck(G)]

The photos do seem to show a parallel-interface drive. The PCB would be interesting.
Sort of like the MicroSolutions Backpack floppy drives. You should see an FDC on the PCB and perhaps a microcontroller.

 

[bolex]

I'm curious to see more pictures of the interface card. If you can provide more pictures that would be awesome.

 

[Chuck(G)]

What doesn't make sense is where the power comes from. That drive takes both +12 and +5--you don't get that through a parallel port. So yes, the interface card would be very useful.

 

[Tincanalley]

That drive was meant for the PS/2 50, 50Z and 70. What are missing is the edgecard that plugs into the second floppy drive connection, the ribbon cable with an edgecard connector on one end and a db25 female on the other end. The cable cares all the data, control signals and power. Inside the drive case a resistors necessary to use the 5.25.

I have one of these and use it on my PS/2 50Z. Bought it back in 1988 and recently pulled out the 360K drive and install a Gotek in it.

 

[bolex]

The CMS floppy line was called the "CMS Transporter".

 

[Tincanalley]

Here are some pics. I have never seen one of those drives being sold complete. I've never seen one with the ribbon cable and edgecard. The ribbon cable is easy, but the edgecard would have to be duplicated by someone with knowledge of such.

 

[Tincanalley]

The CMS floppy line was called the "CMS Transporter".

Out of all the ones I ordered and installed back in the '80s, I never saw one that looked that nice. None of them had the CMS logo as a badge, just painted on. The 360KB was blank and the 1.2MB had a 1.2MB sticker.

 

[Tincanalley]

PCB pic. Just found.

 

[krebizfan]

An old Infoworld shows that CMS had a bunch of different external floppy models under the Transporter name including for Zenith, Sharp, Tandy, and Toshiba. Toshiba had the power passed through the parallel cable when used in floppy mode. Some of the other models came with a power supply and hooked up to an external floppy port. Frustrating not knowing the specifics.

Edit: I don't see a floppy controller on the small board. Could a picture be provided of the lower surface of the board and the rest of the traces from the 25-pin connector?

 

[bolex]

I found this picture on Vogons. These look like they may be the Floppy adapters that would power that 25 pin floppy from the 40 pin PS/2 floppy cable.

 

[Tincanalley]

An old Infoworld shows that CMS had a bunch of different external floppy models under the Transporter name including for Zenith, Sharp, Tandy, and Toshiba. Toshiba had the power passed through the parallel cable when used in floppy mode. Some of the other models came with a power supply and hooked up to an external floppy port. Frustrating not knowing the specifics.

Edit: I don't see a floppy controller on the small board. Could a picture be provided of the lower surface of the board and the rest of the traces from the 25-pin connector?

There is no floppy controller in the unit. The board is really just to add the pullup resistors, etc. The drive depends on a controller in the machine and just passes the data, control signals and power along through the cable. Once in the unit the PCB puts the right resistance for the drive to operate. The floppy drives in the PS/2 50, 50z, 60, 70 and 80. Were not the same electrically as standard drives, so the need for resistors to use them in a PS/2. It is crazy. I hardly do anything with my 50Z as it is so limited in upgrades, etc.

The adapter in the link is the cheapest way of using a standard floppy.

https://texelec.com/product/ibm-ps2-to-standard-floppy-adapter/

 

[Tincanalley]

One last pic. This is inside the drive case. In this case I have had 5.25, 3.5 and now the Gotek. The only thing I changed was the cable from an edgecard for the 5.25 to a pin for the others. I'm not an expert on PCBs, but this doesn't seem to do anything other than fix the resistances needed to use standard drives with the PS/2s.

 

[carlos12]

Here are some pics. I have never seen one of those drives being sold complete. I've never seen one with the ribbon cable and edgecard. The ribbon cable is easy, but the edgecard would have to be duplicated by someone with knowledge of such.

Wow, thank you very much for your valuable help and pics! So it looks like I just bought a brick :lol: because with my (very) limited knowledge on electronics, I see impossible to have the cable and card needed. I feel stuck.

Anyway, it seems like it's not as easy as I figured out, just plugging the unit to the parallel port :sad: Do you think I could damage something if I try?

 

[Chuck(G)]

Yup, no controller. Since power's coming over that 25 pin cable, you can't use it on a parallel port. My guess is that this is half of a two-part setup--the other part being a card in the host. I don't recall if it was CMS, but there were PS/2 setups for the ISA systems (don't know if it was made for the MC ones) that added a "shadow" DOR (port 3F2) to derive additional drive selects and motor control--the output of that then went to the external box. It was safe to do as 3F2 is a write-only port.

Anyway, that's my take.