Silent Q

Azog's little slice of the world. Whee.

P112 build

Posted By on February 14, 2012

The P112 is a venerable Z80 based kit that’s been around for a long time. Is that a redundant statement? It is similar to the older SB180 from Steve Ciarcia, which is no longer available. It’s also somewhat similar to the N8VEM, which is contemporary.

The N8VEM has a different target audience and methodology. I won’t go into full details of the differences, you can find them at their respective repositories, but the major difference is that the N8VEM is not a kit; you need to order every specific part, burn your own ROMs and so on.

I was lucky enough to catch a comp.os.cpm announcement that a few P112 kits were being offered, so I decided what the heck. This is the semi-finished project. Semi-finished, in that I need to find a chassis for it, and etc.

The P112 arrives in a bag o parts:

There are a few SMDs, such as the Z180 CPU, so the kit curator “pre-loads” all the SMDs. You’re left with the rest.

A bucket of components:

And IC sockets and the associated ICs:

So I start off by viewing and printing the construction steps. I think my soldering iron needs a new tip, because lately I’ve been needing to use flux paste on a regular basis. It’s better to be messy from the start, and get it right, then have to go back and do it all over again…

After everything, except the battery holder, is soldered in place, but before installing the ICs, I gave it a nice wash. First a scrub with isopropyl alcohol, then rinsing it off with plain water. You can do that, you just need to be careful. Make sure you get it dry immediately afterwards. Spray compressed air inside all the sockets and stick it under a 100 watt bulb positioned very close. I put a small fan near it as well.

Then once is all clean and dry, a visual inspection for solder bridges or leads in need of trimming. Insert the ICs and give it a shakedown boot, which didn’t work the first time. The kit curator was extremely courteous in his e-mail exchanges, but as always, it boils down to “user error”, so there’s no need to embarrass myself with further details.

First successful boot, pausing at the BIOS. You can see a disk error simply because there is no disk attached to it.

It uses a standard PC 3.5″ floppy, of which I have a few laying about. I created a boot disk from the image file on the CD provided (and not pictured here). There is an IDE interface available called the GIDE, and a posting dating a couple months back was fishing for interest in a production run, but so far, no word.

Now to find an enclosure.


9 Responses to “P112 build”

  1. chris jester says:

    How did you make a working boot disk. I have had no luck

  2. azog says:

    I used NetBSD on my laptop with the command:

    dd if=cpm3.img of=/dev/fd0a bs=1440k

    where cpm3.img is the of the image, or whatever image you’re using.

    If you’re using Windows, you can use Rawrite.exe or Rawrite32.exe, both of which are on the NetBSD home page.

  3. Chris jester says:

    I forgot to say that i made one of each os on the cd to floppy. just cant get it to boot without errors. what drives did you use and cables

  4. azog says:

    For the actual disk images, I can only get CP/M 3.0 and UZI to actually boot. All the other images (CP/M 2.2, Z, etc) simply won’t boot. They don’t get passed the initial “OS Loaded, booting” message.

    I’ve tried a number of different drives. Currently I have a pair of these,

    Those are jumper-less drives, so I am using a 3.5 inch style, 34 pin floppy cable with a twist between the A and B drives, and this allows me to boot CP/M 3.0.

    I’ve tried an Epson SMD340, which seems to work, but I only had one and was unable to get to work in any kind of dual-floppy configuration. Not sure what other drives I have, but once I found these two from Newegg work, that is what I settled on.

    What errors are you getting?

  5. chris jester says:

    Bdos err a: and or Bdos err a: sector err

  6. chris jester says:

    with CPM3.0 says bdos err Perm.

  7. chris jester says:

    could you send me the image of cp/m 3.0 you are using

  8. azog says:

    The CP/M 3.0 image is here,

    I often get the the “bdos err perm”, I haven’t figured out what causes it (tho I suspect it might be caused by simply shutting the computer off, so I’ve taken to ejecting the disk before power cycling). When I get that, I just re-format the disk, and re-write the image, and it seems to work. Try a new diskette, or if you have another floppy drive, try that too.

    I wish I could get CP/M 2.2 to boot, you’re getting better results on that image than I am.

  9. A lot of P112 related software can be found at I don’t run that Sourceforge project. I just run

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