HOW TO RESURRECT A DINOSAUR
By Gary Weber, May 7, 1996

A bit of background... Back in 1984, I purchased my NEC PC-8201A. The thing was amazing. I obtained all sorts of upgrades for it (ROM chips, a modem, more memory), and finally a PIC-Disk drive.

The PIC-Disk was much more than simply a disk drive system for the Tandy Model 100 and NEC 8201. It actually turned your machine into a full-blown CP/M computer. You could either run CP/M and live in that world, or you could use the disk drive to save files from the native mode of your machine. In addition to saving & loading individual files, you also could use it to save complete 32K memory images of your native mode, as a backup mechanism to guard against cold starts.

After a few years I had about 20 3.5" disks of information. Some were CP/M software, but most were simply backups and files from my NEC's native mode.

And then, on January 20, 1990, it happened. We all went out to dinner for two hours, only to come back and find that our house had been robbed. Stereo equipment, computer equipment, televisions, just about everything electronic of any value was gone -- INCLUDING MY NEC PC-8201A with PIC-Disk.

Well, our insurance company was very helpful. I was able to replace most of the items that were stolen. The NEC PC-8201A wasn't available new anymore, but the NEC PC-8300 was. After finding out that the 8300 was completely compatible with 8201 software, I had the insurance company order me one.

But unfortunately, Personal Integrated Computers (the makers of the PIC-Disk) had moved onto other things. The PIC-Disk was no longer available. I purchased a Tandy PDD2 and started over. But, I still had these 20 or so PIC disks that I no longer had access to.

I wasn't able to get in contact with anyone who had a PIC-Disk that I could borrow. For six years, I hadn't been able to get at any of these files.

That is, until March of 1996, when I came across a special piece of software that I never knew about. This piece of software opened the door to those six-year old disks that I'd been holding onto, knowing that SOMEDAY I'd be able to read them. The day had come...

The 22DISK Software

This software runs on an IBM-compatible machine. The "22" in 22DISK comes from CP/M 2.2, which was the most popular CP/M version in operation. It has the capability to reconfigure the disk controller in an IBM-compatible to read any density of CP/M diskette. It knows about 400 different CP/M disk formats, all with varying sector sizes, cluster sizes, etc... It also had the ability to be configured for any custom CP/M disk configuration in case yours wasn't one of the 400 that it already supported.

Well, guess what? The PIC-Disk was *NOT* in its database. This meant that I had to go through the tedious process of identifying all of the detailed attributes about the format of a PIC-Disk. Was it single or double sided? Did it have 40 or 80 cylinders? How many sectors were there per track? What was the byte size of the sectors? What was the writing-order of the sectors on the track? How large was the directory table? In addition to all of that, there were several other odd parameters which the 22DISK documentation helped me determine.

After I was all done, I finally had the proper data to give to 22DISK's definition file. I can't fully explain the excitement I felt when seeing the directory of one of my PIC-Disks show up on my desktop's screen... But it was awesome!

CONFIGURATION

When 22DISK is installed, there is an index database which has all of the information for each format of disk that it can handle. This file is is called CPMDISKS.DEF. If you need to add an entry for your CP/M disk format, you must first decompile the index into a text file using the STRIPIDX program:

     STRIPIDX  CPMDISKS.DEF  CPMDISKS.NOI
Now that you have the CPMDISKS.NOI text file, you can make an entry. The documentation for the 22DISK program takes you through the process of coming up with the information about your CP/M disk's format. For the PIC-Disk, the entry looks like this:

     BEGIN PIC1  PIC-DISK SSDD 96tpi 3.5"
     DENSITY MFM ,LOW
     CYLINDERS 80
     SIDES 1
     SECTORS 9,512
     SKEW 1
     SIDE1 0 1,3,5,7,9,2,4,6,8
     BSH 4 BLM 15 EXM 1 DSM 194 DRM 63 AL0 080H AL1 0 OFS 2
     END 
Now the CPMDISKS.NOI file needs to get compiled back into the index file:
     GENINDEX  CPMDISKS.NOI  CPMDISKS.DEF
That was all there was to do! There are a series of programs in the 22DISK package which perform various disk functions. All you do is tell them which CP/M format you have with a parameter on the command line (in this case, the parameter was /PIC1 indicating the name of the format above).

AFTERMATH

All of the files I had on all my PIC-Disks are now safe on other media. Thanks to 22DISK, I have access to stuff I hadn't seen for the last six years.