This is a new one on me and a curious one at that. A quick search of the internet found a small piece on http://en.wikipedia.org/wiki/Four-Phase_Systemsbut not a great deal and nothing on the company after they were sold to Motorola in 1981.
The machine we have here appears to be a small office machine; It has six serial ports on the back along with a 50 pin connector for an external disk drive. I’m guessing SCSI but I have no proof, I have no disk drive either.
Inside the case is a card cage but it’s a bit stranger than it first appears. There seems to be two buses in the cage. The two boards on the left have card edge connectors and both have 6809 processors. The three boards on the right have three row connectors with pins that look like connectors on a VME bus. One board has a Motorola 68010. The other boards seem to be RAM cards.
When I power the machine up the fan whirs and I can see a couple of LEDs glowing optimistically. I don’t see any activity on the 25 way D type at the back labelled “J1 RS-232”.
The Sharp MZ-80A is an all-in-one machine that’s of a style that was not unusual in the early 1980’s. Think Commodore PET, Intertec SuperBrain. Televideo TS-802 and 803. Even the humble Amstrad PCW range.
The screen Measures approximately 9″ diagonally and has a clear plastic plate in front of it. This is rather reflective as you can see in the above photo. The keyboard is full sized and the keys have a good degree of travel. There is also a number pad on the right.
A cassette recorder is built into the case along side the monitor and to its right. This records at 1200 baud (approx 120 characters per second).
Additional ports such as Centronics parallel and RS-232 serial are lacking though I believe they were available as an option. There is certainly space inside the case and the main board has an expansion connector heading off into the empty space at the back.
Rather unusually, it doesn’t have a resident BASIC interpreter. Instead there is a monitor ROM with very few commands and BASIC and other languages were available on cassette tape and loaded in as required.
A friend at work, knowing that I was interested in retro computing, arrived one day with this splendid example of a Commodore 4032.. Sadly when I powered it up I only got a “Bingley beep” sound but there was at least some signs of life.
I moved around the board with a scope and found the clock looked good, as did the horizontal and vertical video signals.
More searching found that the _INT_ line to the 6502 was low. I reasoned that it should be mostly high. The 6520 PIA controller driving the IEEE port is connected to that line and as I didn’t need IEEE at the moment I pulled the chip out. Power up and Bingo! now running.
I replaced the 6520 and all is now well.
Having read through a few hastily translated bits of the technical reference manual I felt that I knew enough to try and get the floppy drives connected. I wasn’t given an original cable but looking around the back of the card cage and at the drives themselves it looked likely that they needed a 25 Way cable (the manual didn’t say).
Switched everything off. Plugged in a cable. Disks on. Main unit
Drive light comes on for a bit and then goes off. Whoopee.
This is repeatable 🙂 I have since tried a floopy in the drive and get
the same behaviour. I can’t get it to boot but I’m delighted to have got it this