H8 Collection

This H8 system comes with 12 boards. Every board has been tested to work. HOWEVER, please note that I don't use all of these boards all of the time, and each one is over 40 years old, so if they don't work upon first boot, you have a project!

Most of these boards have had some work done to/on them. In the following sections, you can read about the work that was done. The floppy controller has had one (reversable) modification, to allow you to turn off the floppy ROM on the board so that the Z80 CPU board will run well.

The boards have been stored in these padded boxes, which come with the boards.

Click on any thumbnail to see a high-res picture of the board. Thumbnails were used to make this page load much faster.

IMPORTANT - most boards have the original documentation, but some don't. If there is documentation for a board, there will be picture beside the board. The documentation is not listed in the description of the board.

This is orignal CPU board included with the H8. It is in great condition, with no board modifications/fixes.

It has the PAM-37 ROM installed (the "PAM GO" ROM - 444-60).

The documentation for this board is shown in the listing for the H8 itself.

This board is in great shape, and works well. It includes the 444-140 ROM. Note that when using this board, you should turn off the Floppy Controller ROM using the switch.

When I got this board, it had Pat Swain's 3MHz mod applied to it, as was detailed in REMark magazine issue #38 (Mar '83). I've removed the mod because it required a front-panel modification that was incompatible with the 8080 board, and I wanted to be able to easily use both. The board is now back to original condition.

Along with the board is:

• Original Operation/Service manual
• Original large format schematic
• Original large format x-ray
• (other manuals...)

This board serves as the interface between the H8 to the floppy drive. In this case, the interface from the H8 to the H17.

This board has been modified slightly to have a toggle switch in the upper right corner that will turn ON or OFF the onboard ROM containing the code necessary to interface to the floppy drive. This was done because the Z80 CPU board contains its own ROM for interfacing to the floppy drive, and having the two ROMS "on" at the same time isn't a good idea.

So when you are using the Z80 CPU, flip the switch to OFF. When using the original 8080 CPU, set the switch to ON.

The manuals for this board can be found in the Machine tab with in the H17 item description.

There are four 16k static RAM boards with this H8. Each one works great.

Each of these boards has a different serial number that can be seen on the board at the bottom. Click on the thumbnail to see it. This one is: 0000025-41911.

This particular board was a problem child. I could see that someone had worked with the board prior to me getting it. Many of the filter capacitors were removed, and many of the chips replaced. But I don't think that they ever found the problem, it was quite difficult to find.

On this board the address line A6, which is driven by R112, was not reaching memory chips 110, 111, and 112. Turns out that the top-side trace under the socket from 113 is somehow cut - which is a bad thing. I chose not to try to remove the socket and rework the board, risking doing more damage. Instead I simply put a wire on the back side of the board to get A6 to those three chips.

Bottom line is that this board now works great.

Of the 4 boards, 2 of them come with the Operation & Service Manual and diagram sheet including the X-ray (as shown).

There are four 16k static RAM boards with this H8. Each one works great.

Each of these boards has a different serial number that can be seen on the board at the bottom. Click on the thumbnail to see it. This one is: 0000292-43302.

Of the 4 boards, 2 of them come with the Operation & Service Manual and diagram sheet including the X-ray (as shown).

There are four 16k static RAM boards with this H8. Each one works great.

Each of these boards has a different serial number that can be seen on the board at the bottom. Click on the thumbnail to see it. This one is: 0000608-43302.

There are four 16k static RAM boards with this H8. Each one works great.

Each of these boards has a different serial number that can be seen on the board at the bottom. Click on the thumbnail to see it. This one is: 0000425-42672.

This multi-port serial board runs great! But it didn't used to. When I got it, it was completely dead - and turned into a big project. Here's what I did to get the board running:

• Replaced the regulator capacitors.
• Replaced the oscillator. This was a tough one to debug, but I found it! I replaced the oscillator with one that is of the same vintage, but functional.

This multi-port serial board runs great too! And like the other one, this one was completely dead when I got it too, with a few problems:

• Replaced the regulator capacitors.
• Replaced the oscillator. But I didn't have the same vintage oscillator, so I used a more modern one. You can see it in the lower left corner of the board.
• I replaced one of the IN8250 chips - the serial USART. Not bad, that only one of the four on the board was bad.

This is a single-port serial board, but it also includes a cassette interface.

Th serial port is wired to 1200 baud, and works just great. Unlike the multi-port boards, you have to hardwire this board for the speed you want.

IMPORTANT - I haven't tested the cassette part of this board. I just never found the time or need to do it. There are three cassettes in this collection, but I have no idea if any of them have any thing on them. Sorry about that!

I have had this board up and running in the past, but don't have a demo for it.

It comes with the normal cables as well as a modulator so that you can send its output to a screen.

This board is in excellent condition, and completely operational. It comes with:

• Original assembly manual - with checkmarks during assembly
• Original large format illustration booklet, w/Xray and schematic

This board comes with a 64K static RAM circuit wired up. You can keep this circuit or get rid of it, that's what a breadboard is all about. Note that the 64K only works with the Z80 board.