Here's a summary of how to build the adapter cable, for future reference
Ingredients:
- Something that will fit into the 40 pin slot. I used the connector from a broken diskdrive. The contacts are spaced the same as on ISA cards, so you could cut one of those up if you don't have anything else
- A 34 pin floppy drive cable, if you dont have one laying around just get a regular floppy cable at your local computer store.
- A bit of wiring with an FDD power connector, I cut one off a broken powersupply but I'm pretty sure you can buy a molex->fdd converter at most computer stores, then just remove the molex contact and you're good to go.
- Soldering iron
First, let's define pin positions..
The 40-pin end should have have 17+3 contacts on each side of the connector. Pins are as in the pics:
On the 34-pin regular "modern" FDD cable with seperate power cable, one of the outmost wires should be marked with a different color than the others. That marked cable is pin 1. The next one is pin 2, and so on.
Make sure you remove the twist in the cable or the cables may/will be in the wrong order!
On both the 40 pin and 34 pin, all odd pins are ground, with the exception of pin 3 at the 40 pin end, which is reserved. Now in theory, both on your diskdrive and the slot at the motherboard/controller side, all grounds should be the same. So you can save yourself some work and don't need to connect every single ground wire. I only connected a couple of them. That's half the work done!
Now for the pin conversion, this is where it gets interesting!
Code:
40pin 34pin Description
2 x Density Select (I have not connected this, 0=HD, 1=DD)
4 x Reserved
6 x Reserved
8 8 Index
10 x Reserved
12 12 Drive Select (B)
14 x Reserved
16 16 Motor Enable (B)
18 18 Direction In
20 20 Step
22 22 Write Data
24 24 Write Enable
26 26 Track 0
28 28 Write Protect
30 30 Read Data
32 32 Head 1 Select
34 34 Disk Change
36 x Ground (I'm using ground from a different place though)
38 PWR +5V
40 PWR +12V
I had some trouble getting the drive to read HD disks, I found that putting a bit of tape over the HD hole on the disk made it work, even if it was formatted as 1.44 MB. Strange, but true. After running the BIOS setup it now reads both 720k and 1.44 MB disks without problems even without using pieces of tape, with pin 2 (density select) completely disconnected.
Pin 12 and 14 may seem counter intuitive too, but using pin 14 and 10 (Drive Select A/Motor Enable A) for those did not work. So you have to use Drive Select B and Motor Enable B. Your drive will show up as drive A anyway!
Other than that, just connect all of the pins up to 34.
For powering the drive, you need the power cable/connector. There should be 2 black wires (ground), a red wire (+5V) and a yellow wire (+12V). The red wire goes to pin 38 on the 40-pin connector, the yellow wire goes to pin 40. You can solder the black wires to any ground you want on the odd side of the connector, I used pin 37 and 39 as you can see in the picture.
That's all! With a bit of luck, you should now have a working floppydrive! I tested with 4 different drives and only one of them worked, I suspect this may have something to do with the controller not being able to handle the other ones. The drive spins, tries to read, but the result is always the same: Abort, Retry, Fail?
I've ordered a book that should contain a load of technical information about the PS/2 and I will see if it contains any useful information about this, because it'd be great to be able to use just any drive.
The drive I'm using that works is manufactured by ALPS, manufacturer part number DF334H015A. These seem to be available all over the net both new and used.
Good luck
Your finished product will look something like this
