Silent Q

Azog's little slice of the world. Whee.

GIDE for P112

Posted By on April 17, 2012

This is a project I’ve been working on for some time. But it doesn’t work. I normally don’t like to post a half-assed project like this, but perhaps the rant will help me think of something, or perhaps someone will stumble on this and have an idea…

This is the GIDE (generic IDE) kit for the P112. This is built and installed. Hard to tell, but the P112 is below the GIDE, and connects via a three row series of headers near the left. I had to remove the battery from the P112, since it stood too tall to allow the GIDE to install. This is/was a known issue, and you can see that I’ve simply placed the battery on some double-sided tape and ran three conductors of some ribbon cable back to the P112.

The Compact Flash interface is not part of the GIDE kit. I purchased that separately for like $5 on ebay, shipped from Hong Kong. They’re really cheap. There’s no logic on the interface at all. I think CF is actually a subset of IDE.

The 128mb is a card I had laying around, and seemed like a reasonable size for an 8-bit system. For those who’ve never used a CP/M system, and are used to terabytes of disk space, 128mb is huge.

The CF interface is plugged directly onto the GIDE and uses a 3.5″ power connector. IF I ever get it working, I’ll need to preposition it so that it fits inside the enclosure. I wonder if there are 90 degree gender benders for headers? But that’s for a later date…

The GIDE arrives in a kit that is significantly easier to build than the P112. That’s because all the logic is inside two GALs, so the developer of the GIDE must have spent a good portion of time developing the GALs.

There are a couple of options you can select during building, the most important being how the GIDE will install onto the P112. If the GIDE is going on top, like mine, the headers get soldered from the component side. If the P112 is on top, the headers get soldered from the solder side.

I chose to add one other option mentioned in the build guide, a DIP switch for the address selection.

You can see the DIP switch at the upper right, and it is set for 50H, which is the default. I could have hard-wired it with jumpers, or even put a socket, but I opted for a DIP switch because, even tho it’s unlikely I will ever change the address, it gives it a really good visual finish. Yea, that’s a bit of vanity.


The GIDE comes with a boot disk, but it does not boot. If you look at a previous post, I mention I am having issues booting some of the disk images. The provided boot disk behaves in the same way, reporting “OS loaded, booting…” and then ceases.

CP/M 3.0 boots, but when I run fdisk, it reports it cannot read the IDE partition, which I am assuming means it cannot FIND the IDE device.

It these intermittent issues that are causing me frustration. If CP/M 3.0 boots, why doesn’t CP/M 2.2 or Z? Each time I create a disk from an image, I format it, and re-write the image, and then write-protect the disk to make sure nothing gets accidentally erased.

If I accidentally blew the disk controller chip (the other SMT device besides the Z180), I would imagine it wouldn’t boot AT ALL. If I accidentally blew the GALs, then the same behavior above should be apparent.


4 Responses to “GIDE for P112”

  1. Hector says:

    For the boot problem, make sure you are using ALL the RS232 handshake lines. Either connect all of them to your terminal and enable hardware handshaking, or bridge RTS to CTS and DTR to DSR.

    The “OS loaded, booting…” is output via the P112 ROM monitor, which is not that picky concerning the handshake lines, but the CP/M I/O routines are; that’s why the prompt does not appear.

    Hope that helps.


  2. azog says:

    Hi, and thanks for the comment.

    Unfortunately that does not appear to be this particular solution. I’ve manually shorted the pins indicated (RTS to CTS, and DTR to DSR), and the behavior remains, simply displaying “OS loaded, booting…”. I don’t think it is simply a console IO problem, because the diskette LED stays active, and it actually doesn’t feel like the diskette is doing anything, just the spindle motor is turning and the activity LED is solid. Even if it was not displaying IO on the console, I figure eventually the diskette LED would go dark. But after an hour, the diskette LED is still active, and the spindle motor is still turning. I’m guessing that the problem is elsewhere.

    Sometimes you have to call it quits, and I’ve given up on this particular project. I’m just getting up the energy to post it for sale on ebay or something, as a “non-working” project.

  3. Hector says:

    Sorry to hear you gave up on this project, I believe I could help. I still have my P112s running (one still controlling a measuring instrument for more than 10yrs of continuous work) and have some experience with it.

  4. azog says:

    If you’ve any ideas where to go from here, I’d certainly be willing to try anything. I hate to give up, but it’s been collecting dust for a few months now, and I’ve no real idea where the problem exists. Heck, I’d even be willing to send you my P112. Given the nature of the problem, I’m adamant that it must be something simple that I am doing (or not doing).

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