Quote:
Originally Posted by NealCrook
Hello cosmocat, hello jncoleman. I started a new thread to describe my NASCOM projects, which you might be interested in.
@cosmocat: I can lend you a PolyDos boot disk, but it is 35-track DSDD (350Kbyte). Another way is to use my SDcard adaptor connected to the PIO. It uses a special version of the Polydos ROM. You could probably use it as a way to boot-strap to a real disk drive.
@jncoleman: I'd be interested to hear about the history of your 3 machines, as I guess at least one of them must have had to earn its keep in its younger days. My own NASCOM 2 (+MAP Video/Floppy controller + MAP 256KRAM) was only ever used for "self-education" purposes.
Neal
|
Apologies for the delay in replying, but I've got three ongoing restoration projects and I thought it would be nice to get something finished and show you some operational pictures. Like other contributors, I'm very keen to preserve these machines for posterity, and I'm also interested in historical authenticity, not only in the functional aspects but in every other respect as well, so I want to keep these machines looking as they were designed, running their original software on the jobs they were intended to do. In each case, therefore, I'm aiming for as complete a state of expansion as possible, with the equipment in its original enclosures, with original matching peripherals, software and documentation, and with a clean separation between the different manufacturers. I'm trying to keep written records along the way.
MACHINE 1 began with a Nascom 2, 48K RAM-B and I/O board, with the Nascom keyboard and Phoenix monitor (the round-looking one often seen in Nascom sales literature). These were housed in a desktop case made by one of the aftermarket suppliers, but as this didn't come with a card frame the two upper boards had to be balanced on cardboard spacers, which wasn't great, although it ran NAS-SYS 1 quite successfully. I moved it all into a 19" rack, and expanded with a Gemini floppy drive, Gemini Winchester, FDC and IVC (later SVC), MAP 256K RAM, Microcode 14-slot backplane, and Gemini keyboard. This ran CP/M 2.2 with the MAP BIOS and Gemini-format disks.
As an aside, I made a useful expansion board for this. Nascoms operate at 4 MHz. Analysis of the memory timing and worst case speed paths showed that, on my system at least, things would work correctly at 8 MHz except in M1 and I/O cycles. So I fitted the 8 MHz CMOS chipset and designed a clock board that generates an 8 MHz signal except in the two cases mentioned, when the speed is dynamically reduced to 4 MHz. The peripheral boards continue to operate at 4 MHz by means of the AUXCLK bus signal driven by the original Nascom clock, and a setting in the BIOS allows for the correct operation of timing loops. The improvement here was quite dramatic, even in applications I wouldn't have thought were particularly CPU-bound.
When this entered service everyone else was using Windows, but I like the austere engineering beauty of a system in which I know exactly what is happening, with no processes I didn't explicitly start, and with fully documented hardware. I used this machine for my Ph.D., which caused comment, and extensively afterwards.
This machine came to an end when the drives and monitor were accidentally thrown out at work. However, for the reasons stated above, I took the opportunity to separate the parts from the different manufacturers and revert to a rack-based Nascom-only. Nascoms were intended for use in both desktop and embedded control applications, and the rack-mounted configuration is more suited to the latter, not least because it obviates the need to find a keyboard enclosure that matches the system cabinet. My remaining system now comprises a Nascom 2 at the original 4 MHz clock speed, RAM B and I/O. These are mounted on the Microcode backplane (now cut down to 10 slots) and are shown in picture 1. The 1U front panel is a remnant of the previous hybrid machine and still has all its connectors; it will be replaced with a simpler one that just has the PIO and UART interfaces. I can't show it in operation because it isn't used for anything yet, but 'when I've more time' is going to be used to control the model railway.
MACHINE 2 is a second-hand Nascom 3, the fully-fitted desktop system with Nascom 2, FDC, AVC and 'Nascom' 256K RAM (actually made by MAP-80). After ten years of disuse in the attic it came to light when we moved house recently, and didn't work. After programming a new boot EPROM, the next problem was the drives, which look to have been very early ones. Refurbished Cumana ones were obtained from the suppliers on ebay. I know Nascom did use Cumana drives, latterly the slimline versions, and although the bezels would have been black, I think these are reasonably authentic. Finally the RAM board was unreliable, the M drive frequently losing data. This too was an early version, with DRAMs of the slowest speed grade, and was conveniently replaced with the faster one left over from machine 1. This machine runs CP/M and is shown in pic. 2, together with the matching Lucas dot matrix printer.
A Nascom 3 has two display controllers, the standard Nascom 2 48x16 monochrome text display, and the AVC; these can be used simultaneously. The AVC operates in two modes: high resolution monochrome and medium resolution colour. Pic. 3 shows the hi-res mode, compiling my LISP interpreter that I wrote using HiSoft Pascal, and I'm now using the machine to continue this work (the photo had to be taken at maximum pixels, and had to be compressed). Pic. 4 (likewise) shows the colour mode: the AVC output is sent to a separate colour monitor, while the monochrome monitor is switched to the Nascom 2 display and used for menus and commands, shown here running Nascom's LOTTI 2D drawing package.
MACHINE 3 is an Gemini Galaxy that I'm now restoring. Again, for historical authenticity, I want to get it exactly as Gemini's designers envisaged it. I'll use this to run all the software that I lost the use of after the demise of machine 1. A Galaxy I came up on ebay recently, without drives, but including the GM813 CPU/RAM, SVC, FDC, RAM-disk and Climax colour board. At the moment it's having to borrow the Phoenix monitor and Cumana drives from the Nascom (pic. 5).
At present it doesn't work; the CPU seems to be producing sensible signals at its bus interface but the SVC isn't communicating with it. I'll hopefully sort this out soon. It will be running CP/M 2.2 with the standard Gemini BIOS 3.2, and I'll let you know of any significant progress. Meanwhile, if anyone has a Gemini drive enclosure (with or without a drive) or a Phoenix monitor that they would be willing to part with, I'll be pleased to offer a good price for it.