Ampro, the Easy DIY Computer
Why Build an Ampro?
The Ampro is a very simple computer to build up. If you're looking for a quick project, and want a computer that can run all sorts of software, the Little Board is a great choice. It stands out from the consumer systems of its day like the Commodore 64, Atari 800, and Apple II. Its simple design is well suited for building up a highly customized system, as well, as the hardware itself is easy to get up and running and its small size and flexible I/O make it easy to build it up into a wide variety of cases and enclosures.
One of my original ideas for this system was to build it up inside a goldfish bowl or clear cookie jar. Just about anything you can put a floppy disk drive in is a possible enclosure for this system. Combine this board with 3.5" floppy drives, a small SCSI hard disk, and a small PC power supply and you've got a powerful but compact system.
As it is, I built my system up in a PC's box for now, but with the intention of finding it a nicer home later. I have the new enclosure now, and soon the Ampro will be in it.
Getting It Going
The First Go
Loose on kitchen table with cables running all over.
One night I decided I wanted to get one of my CP/M systems going. I have several, at the time I didn't have any of them set up for regular use. They rotated in and out of may garage every so often. But I wasn't in a position to have any off them up and ready for use any time. Also, all the systems I had at the time were "fixer-uppers". Each one had some reason that I couldn't just use it normally all the time. They all needed some sort of work, or special accomodation. I wanted a system I could just use.
I wasn't in a position to complete the work on any of my fixer-uppers. But I had these two Ampro Little Boards in a box in the garage. I knew the Ampro was a simple, easy to configure system. I pulled them out, and discovered that they were the later version of the Little Board, that they had a SCSI interface! I opened up the manual I'd received with the boards and gave it a read.
After thinking things through, I realized I had everything on hand I needed to set one of these up as a complete system in an evening. I pulled a terminal out of the garage, a couple of floppy drives out of a desk drawer, my serial SmartCable out of another drawer, and a loose PC power supply out of a stack of the same. I left off the hard disk for another evening.
Above you can see a picture I took with my cell phone when I first set up the Ampro. The parts were laid out loose on my kitchen table. The Little Board was set on a cardboard box. I jumpered the PC power supply so that it would turn on without a PC motherboard. I put together a DB-25 adapter for the Ampro serial port plug using the pinout in the Ampro documentation. I set the jumpers on the floppy drives (the Ampro uses the floppy disk select lines correctly, unlike a PC), hooked everything up, said a silent prayer, held my breath, and switched power on.
My Ampro Little Board, fired up for the first time.
It started spinning the floppy disk drive. I pushed in the Ampro-provided boot disk, said a short prayer, and closed the door. It worked! The disk was good, the cabling was good, and the SmartCable meant that the terminal talked to the board without me having to play around with my serial adapter and worry about its wiring.
I spent the rest of the night going through the Ampro disks, making copies so that I wouldn't have to use the originals, and playing around with the provided utilities and programs.
My original system configuration used only a pair of 5.25" floppy disk drives. And I couldn't just leave the system on the kitchen table indefinitely. After the first night, I had put the system's parts away. On the second night, I pulled out a couple of 3.5" disk drives and a PC's beige box to mount up the hardware until I'd have a chance to put the system into something more interesting.
I checked out the additional floppy disk drives on the kitchen table, then started moving everything into the PC beige box.
The guts of the Ampro in its box.
The hole pattern didn't exactly match the Ampro no matter how I lined it up in the box, but I was able to work out mounting the board well enough for a temporary set-up. I would have mounted it on top of one of the floppy drives, but with two floppies there wasn't room in this particular box. Fortunately, wiring up the power and data cables was simple once I had the board in place.
Adding a Hard Disk
When I looked at the software I had, I found that the hard disk software I had was source code. My boot floppies didn't have compiled versions of the hard disk software. They seemed to be new enough, and be for the Plus version of the board (with SCSI), not just for the original Little Board. But no hard disk programs except on a disk of Ampro source code. So I made up 3.5" boot disks where there would be plenty of working room to compile the code and include all the Ampro utilities.
I also started looking at what I had in SCSI hard disks. The Ampro could use up to 88MB of hard disk space, I wasn't sure if it would work with a larger disk, but I knew I had some drives around from the sub-100MB days. Unfortunately none of them were SCSI. They were all ST-506 interface.
So I was looking at what to do. I knew I could turn up an interface between ST-506 and SCSI, possible somewhere in one of my own boxes (hopefully still functional). The other possibility was using a larger SCSI disk drive. I wasn't sure if that would work, but decided to give it a try, particularly since I had other plans for my ST-506 disk drives.
Fortunately, using a larger hard disk than the Ampro could use was not a problem. The first hard disk I connected to the system was an old Quantum 420MB disk. It worked, but it ran very hot. The inside of the box heated up quickly. The other small SCSI disks I had are all spoken for, so I pulled a 2GB out of a box and tried again.
Once again, the Ampro had no problems talking to the disk. I was able to set up my boot disk to configure the drive as disks F: through P: with a total of about 88MB of disk space. At that point CP/M runs out of space for tracking more disk. I set up CP/M for a 56KB Transient Program Area, which gives me the maximum space for maximum hard disk. So far, this has been enough for all the software I run. Once upon a time, on another system, I was always pushing for as big a TPA as possible. I would never have accepted anything less than a 58K TPA, and usually had (thanks to some tricky programs) 61K of TPA out of 64K of RAM. But none of my software minds running under 56K right now, so I'm not sweating it. I'm unlikely to ever need more than half the hard disk space I have assigned on the Ampro, but what the heck. I had maximum TPA on another system, why not maximum hard disk space on this one?
The Ampro's original box, under my desk.
Finding a Home for the Ampro
All this time, the Ampro was living on an end table in my living room. Not where I normally keep a computer (except for a little Eee PC netbook, which fits.) This couldn't last, but I didn't have room for this system on my regular computer desk, which was occupied by a 20" iMac and a PowerMac G3 beige box. Fortunately, I was offered a larger desk by Vic Maris of StellarVue Telescopes. He didn't want it tying up space at his business, and I figured I could fit it in my computer room if I greased the corners and didn't mind denting the drywall.
My new desk, with room for 3 computers.
The terminal I used with the Ampro was my smallest one, an ADDS 2020. Because I didn't have much space for a terminal in the living room. Once I got it on my new desk, I started making adjustments to the display since I have a window behind my desk, which is a problem for seeing computer displays. After a bit, I realized I had room to use a better monitor I had in the garage, a VT-102.
I put in the VT-102, and, of course, I needed to change the cabling for the new terminal. Out came the SmartCable again. I got things talking and was able to put in a serial cable that made both the terminal and computer happy. Then the SmartCable went back to the bullpen, waiting for the next time I hook up something on a serial line.
The next step was to get all the software changed over for the new terminal. Fortunately, the DEC terminals are very well supported. The last step was to tweak a potentiometer inside the VT-102 to make the characters all the correct height. Thanks to some assistance online and the technical manual for the VT-100 series at VT-100.net I was able get the VT-100 back up to DEC spec with little trouble.