Slice of Pi?

Yes, my Commodore PET printer (Epson TX-80 with IEEE interface) cost around £400 - very slow, printed a blank line by eighty spaces. My Star NB24-10 cost £394+VAT in October 1998 and was still printing labels fifteen years later.

Being a tightarse, I procured an old IBM Golfball from British Gas, used vero to wire solenoid drivers and wrote a simple driver. And i'm STILL a tightarse :D

(Interesting site BTW; it even listed a couple of machines that I designed! The electronics anyway; I wasn't responsible for the style..)

No, as far as I recall all of the standard PC chips were present (the

PC at one point, housed in a large white metal desktop case (heavy-duty steel, but not very good construction; sharp edges, weird internal angles, brackets to hold things together etc.). Looking at the Advance

Now it's got me wondering if what I had was essentially a prototype A-86... or perhaps Ferranti made an attempt to market a machine themselves based around the same internals.

Sadly the system went off to landfill years ago; I never could get it to boot any of the media that I had, and I had little reason to keep a non- functional machine which looked as though it might be vaguely IBM- compatible at best. If I'd known at the time that the internals were A-86 then perhaps that would have given me a way of getting it running.

cheers

Jules

they could have been custom gate arrays. I designed some into one of the SystemX boards i designed.

They were arrays of 2 input NOR gates which you designed the metal layer to interconnect them into flip flops, etc. It was all very manual, first you designed the logic and then you taped the metal layout to make the mask.

I think they came later, but very likely the same PCBs. The Ferranti ones I remember (probably the ones you're thinking of) had a front grille with diagonal slots. I think the original guy sold them the rights, hence the PCBs. The major change they made was the metal case (the original plastic required a craft knife to open up the back of an expansion slot).

(incidentally, the person behind the A-86 was previously into digital watches, which we all thought was a joke because of the black plastic case!. It was also referred to as 'a black machine with black controls' - some will get that joke too).

See above.

I did say earlier that they were ULAs.

I think mine had horizontal slots on the front grille. The disk drives were in the same position as on the A-86; the 'Ferranti' logo was black, but I can't remember the exact position now. There was no built-in compartment for a keyboard.

Another bodge-like quirk I just remembered (in common with the A-86 it seems) is that the machine had two power supplies. I don't recall if one just handled +5V and the other did all the other rails, or if the split was between the two PCBs which occupied the upper and lower half of the system.

The machine bristled with ULAs; I suppose it did have quite a bit of on- board functionality (e.g. video) when compared to a 5150 or 5160 from IBM. I remember those horrible aluminium heatsinks on many of the ICs; they were just glued on and would fall off very easily.

cheers

Jules

There was a *lot* of onboard functionality compared to the IBM 51{5,6}0. It had a serial port, parallel port and video, and also a game port.

My machine didn't have heat sinks (it was one of the first three that WHSmith in Croydon got into stock). I heard about the heat problem on the grapevine and reported an intermittent fault so I'd get an engineer visit! It was SOP to fit heatsinks on such visits.

I also got an updated BIOS, when they produced their own. That was after IBM had threatened to sue (I remember this was covered on a BBC radio programme 'about computers'). The original one even replicated the long standing bug in the IBM BIOS where the serial port could not be set up correctly due to the omission of an H in the source code.

IIRC it was the Advance 86 that got Ferranti into trouble from IBM - they had outsourced the program development of the BIOS but the fellow who did it just copied the BIOS in an IBM PC and flogged them that! No wonder the bug was still present. It was certainly either the Advance 86 or the later PPC (in a brown / tan coloured case.

AWEM (ex Ferranti)

It was definitely the Advance 86 (as I said above). Yes, it was the guy they outsourced it to who was the problem. Given the speed with which Advance rushed out the replacement BIOS, they must have bought one in and patched it where necessary.

(the IBM BIOS would not have worked 'as is' due to a subtle difference in the way the 8259 interrupt controller was addressed)

I didn't realise this was an IBM PC-compatible.

I also had a go at a PC-compatible board, around the same time. But my design was based around the 80188 (8088 with integrated peripherals). It would have taken a lot more than a tweak to use IBM's BIOS!

Shame actually, as it made a nice compact motherboard (we were hoping to create a laptop computer - in 1984!), and the on-chip peripherals were more advanced that the discrete versions.

It was - at the BIOS level. It ran MS-DOS 2.0, and I had a copy of PC-DOS

At the hardware level, the interrupt controller was problematical. I remember fixing several programs that worked at the hardware level (e.g. Kermit) because of that.

As I recall, the 188 (and 186) didn't have integrated peripherals, but it did include the DMA controller, interrupt controller, reset chip and maybe the 82155 peripheral controller. But there were some hardware differences that meant a 188/186 could never make a true IBM compatible.

By peripherals I meant these built-in controllers (and there were 3 timers too). The Intel datasheet also calls them peripherals.

It was soon apparent that it wouldn't be fully compatible, but the main problem was software: we wanted to write our own version of DOS, and there were some difficulties with that (possibly to do with reverse-engineering MS-DOS, but that was someone else's job).

Interesting. My Ferranti-branded one certainly didn't. That could have been a hardware fault, or possibly Ferranti had mucked around with mine such that it was subtly different to an A-86.

Mind you, I can't remember for sure how the floppy drives connected - was there an on-board FDC? I notice that the A-86 on old-computers.com has a separate FDC card fitted. If I had to fit a FDC card then most likely I would have borrowed one from my 5150 or 5160, and perhaps the Ferranti machine didn't like those for some reason...

cheers

Jules

Also had the 8254 interval timer functionality, some programmable chip select generation logic and a few other bits.

(you can get 186s these days with UARTs and communications elements as well).

It was not so much the hardware, but the Peripheral Control Block - which was a bank of control registers mapped into address space. That had to sit somewhere (you could move it from its default location), and would thence be sat there waiting to be accidentally poked by some wayward bit of software, at which point anything could happen.

Research Machines did some Nimbus PC "Almost" compatible with a '186

As I said, I had a very early one. The FDC was onboard (an actual 8272, or uPD765). The only reason for a separate card would be aftermarket, to support 3.5 inch drives.

That's what I was referring to. It was a different way of doing things from the 8086/8088, so it wasn't compatible at the hardware level. The control registers were not the same to operate.

It did have a few new instructions though!