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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 18th Jun 2024, 12:10 pm   #1
TonyDuell
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Default Intellec 8 Mod 80

The attached photos show my Intellec 8 Mod 80 computer that I actually need to use on my bench (it's the only machine I have that will read and program 1702A EPROMs). It's based on the 8080 processor, has a lights-and-switches front panel and a machine code monitor in ROM.

Originally it would have been used with a Teletype Model 33ASR terminal, but I'm using an HP95LX palmtop with a home-made current loop interface as it's rather easier to get on the bench.

I've had to replace 3 TTL so far which is not too bad for an almost 50 year old machine.
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Old 18th Jun 2024, 1:43 pm   #2
SiriusHardware
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Default Re: Intellec 8 Mod 80

I imagine the EPROM programmer was just something that it was equipped with to make it possible to create custom firmware which would run straight from switch-on. How were these originally used, or envisaged to be used?
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Old 18th Jun 2024, 5:04 pm   #3
TonyDuell
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Default Re: Intellec 8 Mod 80

It was designed as a development system for 8080 programs.

The normal configuration (which is what I have) was 8K RAM from 0 to 1FFF and a 4K EPROM board from 3000 to 3FFF. The EPROM board is half-filled by the system monitor program which lets you edit memory, read and punch memory to IntelHex or BPNF format paper tapes, display registers, program/read EPROMs in the front panel ZIF socket etc.

You can use the other half of the EPROM board to hold you own programmed EPROMs. You can,of course, run programs directly from the EPROM board whereas you would have to copy the data from an EPROM in the front panel socket to RAM to run it.

You can have an EPROM board and RAM board at the same address. There are DIP switches on the former to enable/disable each of the 16 EPROMs on the board. If have EPROM and RAM boards at the same address then if you disable an EPROM, the corresponding 256 bytes of RAM are enabled. A sort-of EPROM emulator.

Note that the memory map starts with RAM. At power on, you load a JMP instruction into the first 3 bytes of RAM using the frontpanel then reset the processor. That's how you start the monitor program running.

The monitor supports console, punch, reader and list devices. Just like CP/M some years later. There's even the same IOBYTE at location 3 to determine the device mapping.

According to the user manual there was a text editor (line based, of course) and 8080 assembler available on paper tape that you could load into the machine's RAM. I don't have those, alas.
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Old 18th Jun 2024, 7:20 pm   #4
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Default Re: Intellec 8 Mod 80

Quote:
Originally Posted by TonyDuell View Post
According to the user manual there was a text editor (line based, of course) and 8080 assembler available on paper tape that you could load into the machine's RAM. I don't have those, alas.
Like these? I wonder if Museums Victoria have the ability to dump the tape contents? They were very helpful when I requested some information on their LCDS.

https://collections.museumsvictoria....query=Intellec
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Old 18th Jun 2024, 10:12 pm   #5
SiriusHardware
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Default Re: Intellec 8 Mod 80

Oh, dear, that looks exactly like what Tony is after. If they could be persuaded to lay it out flat and take a video panning from one end to the other* , would that be enough to be able to reconstruct the code from?

I'm not at all familiar with punched tape but I assume those holes in the first part are sync or index markers, so there will be one byte running side to side across the tape per index hole? Should be possible to read that by eye, provided you have a video of the whole thing? We could have a lot of fun if we all looked at it individually and all attempted to come up with the same result.

Or, maybe they have something on site which can read it for you? It all depends on whether they are prepared to put it through the stress of being dragged through a machine / a reader one more time.

* Thinking about it, it would be better to mount the video camera at a fixed distance and fixed focus above the desk looking straight down on it, and then drag the whole tape smoothly past underneath it.

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Old 19th Jun 2024, 5:41 am   #6
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Default Re: Intellec 8 Mod 80

I seem to recall seeing an Intellec on display last year? at the Cambridge CfCH
- At the back of the main room, as part of a special display at RCF2023?

Not sure if this was in their collection, or whether someone brought it to the event - Will have to try and find my photos, unless anyone else recalls it / what model it was.
If the CfCH does have one, then maybe they have some software for it ?
I wonder if it could also take input from other (magnetic etc) media?
Or at least download more-constant speed Async-serial data into RAM etc.


I recall CP/M also needing RAM starting at 0000h and being a reason why you couldn't get a ZX Spectrum to run it as ROM was in first 16K of Memory-map.
But if that's the case / some CP/M machines had full 64KB of RAM, then I presume they must have had some way of automatically jumping from Z80's 0000h reset-vector at power-up (Possibly by paging lower-16K etc memory-map between ROM and RAM?)
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Old 19th Jun 2024, 11:31 am   #7
TonyDuell
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Default Re: Intellec 8 Mod 80

As standard the Intellec 8 Mod 80 has one I/O board. This has 4 output port and 4 input ports, some of which are used by a UART on the board for the teletype interface. It also controls the EPROM programmer and provided parallel interfaces for a high speed paper tape punch (typically about 75 characters/second, something like a Facit 4070) and high speed paper tape reader (about 500 characters/second). Reading in a paper tape on the teletype, while possible, is very slow (10 characters per second) and hard on the tapes.

The interfaces for the tape punch and reader (essentially 8 data lines, strobe and ready) are documented and it is not hard to link other things to them. You could link a more modern machine to them

The built-in serial port will run at 2400 baud, 1200 baud, or 110 baud by setting a jumper on the I/O PCB. It's 8 bits no parity from what I remember. Again linking it to something more modern is easy.

As I mentioned, you could assign physical to logical devices, much like STAT in CP/M. There were used-defined devices, you wrote a driver for them and pointed some jump vectors to that. All this is documented in the manuals (the hardware manuals are on bitsavers, but there's also a software manual and a ROM source listing that came with my machine)

The machine could take another 3 I/O boards. According to the manual these could either be the same as the standard one (although normally the UART wasn't fitted or was disabled to provide lots of parallel ports) or a board with 8 output ports (and no inputs). I would therefore think that using the machine as an embedded controller was a possible application. You can configure it to have a ROM board at address 0 if you want to.

As for paper tape, the row of small holes is the 'sprocket track'. On slow readers it's literally that, a toothed sprocket wheel engages with the holes. On fast readers the holes are detected optically and used as a timing clock. There are then 5 data holes on the wider side of the tape, 3 on the narrower. These represent binary bits (hole=1, no hole = 0), the '5' side is the most significant.

While you can punch pure binary data, it is very likely that the Intellec tapes are ASCII characters using the normal Intel Hex format. The monitor ROM can read/punch Intel Hex tapes and the manual certainly implies the editor and assembler are loaded that way.

As regards stress on the tape from reading it, a good optical reader, like a Trend UDR700 is very 'kind' to the tape. It feeds the tape using a capstan and pinch roller mechanism and senses the holes optically. I've never damaged a tape when using one.

And as for CP/M, the normal version needs RAM at location 0, it was developed on an Intel MDS which is a later machine with a Multibus backplane and 8" disks (yes I have one...). That machine has RAM at location 0 for much the same reason that the Intellec 8 does. Most microcomputers that ran CP/M had a boot ROM that was switched into the memory map at location 0 on reset, the processor executed that. Often the ROM could be bank-switched with the top section of the RAM after the machine had booted.
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Old 20th Jun 2024, 3:24 pm   #8
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Default Re: Intellec 8 Mod 80

Quote:
Originally Posted by ortek_service View Post
I seem to recall seeing an Intellec on display last year? at the Cambridge CfCH
- At the back of the main room, as part of a special display at RCF2023
That might have been my Intel SIM-8. The museum does have at least one Intellec 8 but I don't think much has been done with it. I do know that one of the volunteers, Jon Hales was working on archiving a lot of information on it though.

Cheers,
Dave
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Old 21st Jun 2024, 2:40 am   #9
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Default Re: Intellec 8 Mod 80

Thanks Dave for the photo of your Intel SIM-8 - It wasn't actually that which I'd been thinking of, but a (Blue?) cased system, that I had a recollection may have actually been a 16bit / Nat Semi system.

However, co-incidentally, I've just picked up my CfCH RCF 2023 printout of the exhibitors, and have seen you also had an NS IMP-16 (as well as a Model 33 Teletype). So I do now remember it was actually that Dev. system for a rather uncommon early 16bit Nat Semi processor
(One of Nat Semi's many not-too-successful attempts over the years at getting into the processors market, with maybe only the COP(8) ones getting significant use).

And good to know they do have an Intellec 8.

I've just realised it seems the 8080 was launched in April 1974: https://en.wikipedia.org/wiki/Intel_8080
So now just over 50years old, and maybe due a special anniversary event at CfCH etc....
- Certainly there could be a v.large display of Z80 machines for their 50th in a couple of years
(Or for the 6502's 50th late next year, just before the RCF)
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Old 21st Jun 2024, 8:52 am   #10
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Default Re: Intellec 8 Mod 80

Quote:
Originally Posted by ortek_service View Post
I recall CP/M also needing RAM starting at 0000h and being a reason why you couldn't get a ZX Spectrum to run it as ROM was in first 16K of Memory-map.
Yes, that's why the Polish re-imagining of the ZX Spectrum, the Elwro 800 Junior, has a hardware modification such that, by poking a particular bit, the memory map gets rearranged to put RAM starting at 0000. It will then run CP/J, a modified version of CP/M which was intended for use over a network (Junet) in schools. A bit like the BBC Micro's Econet but, so I hear, without the benefit of actually working properly.

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Old 21st Jun 2024, 2:10 pm   #11
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Default Re: Intellec 8 Mod 80

Quote:
Originally Posted by ortek_service View Post
However, co-incidentally, I've just picked up my CfCH RCF 2023 printout of the exhibitors, and have seen you also had an NS IMP-16 (as well as a Model 33 Teletype). So I do now remember it was actually that Dev. system for a rather uncommon early 16bit Nat Semi processor
Yep, the IMP-16. A rather strange system. Need to get back to that and try and getting it doing something a bit more interesting

Quote:
Originally Posted by ortek_service View Post
I've just realised it seems the 8080 was launched in April 1974: https://en.wikipedia.org/wiki/Intel_8080
So now just over 50years old, and maybe due a special anniversary event at CfCH etc....
Yeah there are a few big anniversary's coming up. 50 years since the launch of the Altair 8800 next year too.

Cheers,
Dave
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Old 21st Jun 2024, 2:21 pm   #12
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Default Re: Intellec 8 Mod 80

Ah, its just clicked. Sorry, I'm a bit slow
You're devlish Dave?
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Old 21st Jun 2024, 2:31 pm   #13
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Default Re: Intellec 8 Mod 80

Yep, Devilish Design on the socials. Just Dave IRL
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Old 22nd Jun 2024, 10:49 am   #14
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Default Re: Intellec 8 Mod 80

Quote:
Originally Posted by cmjones01 View Post
Quote:
Originally Posted by ortek_service View Post
I recall CP/M also needing RAM starting at 0000h and being a reason why you couldn't get a ZX Spectrum to run it as ROM was in first 16K of Memory-map.
Yes, that's why the Polish re-imagining of the ZX Spectrum, the Elwro 800 Junior, has a hardware modification such that, by poking a particular bit, the memory map gets rearranged to put RAM starting at 0000. It will then run CP/J, a modified version of CP/M which was intended for use over a network (Junet) in schools. A bit like the BBC Micro's Econet but, so I hear, without the benefit of actually working properly.

Chris
Thanks for the info - I wonder how practical it would be to mod an original Spectrum to support CP/M ?
I recall the Plus 2/3 (and probably the 128) had various memory bank mapping configurations (Mostly implemented in the extra Logic Array) to set how the RAM (and ROM) banks were placed in the Memory-map (Inc. some having multiple locations / it started up with '128' ROM and then could reset with original 16K/48K ROM mapped in place.
And I presume it could then run CP/M (Like the Amstrad CPC).

I also recall Torch Z80 Co-Pro's for the Beeb running their own 'CP/N' version, but not sure what the difference was compared to original CP/M.

CP/M was always a bit of a multitude of (Disk format) standards unlike MS-DOS, so made program & data exchange rather awkward. And CP/M86 must have been even more non-standard with a different instruction set!
(Maybe like early attempts at Unix on a PC, wth Xenix, before Linux caught-on (although being free & open-source probably helped as well as starting out with integrated GUI so more Windows-like than different mainly command-line only OS's - like OS/2?)
And I seem to recall there was akso a multi-tasking 'Concurrent' version of CP/M

I'd not heard of Junet before, but not that many Schools used Spectrums which probably weren't too robust in classroom use compared to Beeb's (And even those had their issues - Mostly with added Solidisk Sideways AM expansions at my School, which I helped fix as they needed wires soldering-in to make them more reliable)
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Old 22nd Jun 2024, 10:50 am   #15
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Default Re: Intellec 8 Mod 80

Quote:
Originally Posted by Moonferret View Post

That might have been my Intel SIM-8. The museum does have at least one Intellec 8 but I don't think much has been done with it. I do know that one of the volunteers, Jon Hales was working on archiving a lot of information on it though.

Cheers,
Dave
If you don't already have it, you might want to get :

Intel_8008_8-Bit_Parallel_Central_Processing_Unit_Rev4_Nov73.pd f

from :

http://www.bitsavers.org/components/intel/MCS8/

which contains a bit of information on the SIM8 and related products including the circuit diagrams.
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Old 22nd Jun 2024, 12:12 pm   #16
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Default Re: Intellec 8 Mod 80

Thanks for that info - I'd presumed the SIM8 was (as well as the Intellec 8) also for the 8080.
And I imagine SIM8 is probably even rarer than the Intellec 8 - But not sure if the Intellec 8 was originally also for the 8008 (hence the name) and the Mod 80 version added support for the 8080?

The 8008 never really seem to have caught on (I've not seen anything commercially that used one), maybe as it originally cost rather more than even the 4004 - Although not quite a much as an 8080's (or 6800) original price when that was first launched!

I did recently discover that the later 4040 version of the 4004 was rather cheaper than the 4004's original price at $29? for the full 4040 chip-set that was needed to be able to use the 'CPU' IC.
And so led to the 6502 aim to be sold at $20, by using much-smaller die than the 6800 as it used later true NMOS technology and simpler instruction architecture to keep costs down.
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Old 22nd Jun 2024, 12:26 pm   #17
TonyDuell
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Default Re: Intellec 8 Mod 80

Yes, the original Intellec 8 (MCS8) was 8008-based, the 'Mod 80' (or MCS8i) was 8080 based. The 2 machines shared many PCBs, essentially the processor board was the main difference. I am pretty sure there's a manual for the 8008-based one on bitsavers, it may be under 'components' !

There were few 8008-based computers, although it did turn up in some video terminals. There's a Beehive B601 on my bench at the moment which uses one, this is what started the thread on 'dripping CRT' in the TV section of the forum and indeed why I need the Intellec 8 (to read some 1702A EPROMs)

Probably the most common place to find an 8008 though is on the frontpanel keypad/display controller board of the PDP11/34 computer.
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Old 22nd Jun 2024, 8:12 pm   #18
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Default Re: Intellec 8 Mod 80

Quote:
Originally Posted by ortek_service View Post
I'd not heard of Junet before, but not that many Schools used Spectrums which probably weren't too robust in classroom use compared to Beeb's
Without wishing to get too far off topic, Junet is unique to the Elwro 800 Junior and was only ever used in Poland. It's unrelated to the "network" port on the Sinclair Interface 1. The 800 Junior was intended to be the Polish equivalent of the BBC Micro and was indeed used in schools but was never really pervasive: only about 30,000 were ever made. And its plastic case was originally designed for a toy piano, complete with music stand!

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Old 27th Jun 2024, 8:45 am   #19
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Default Re: Intellec 8 Mod 80

Just found this fine web forum after a little light searching for 'Intellec 8 mod 80' microcomputers. I'm restoring an Intellec 4 mod 40 (from my college days) and I'm missing the native assembler tape. (WTH didn't I keep a copy from 50 years ago?) I'd spotted the museum copy of the 8080 assembler early last year and I've been asking them nicely if a copy (paper or electronic) could be made. The idea would be to reverse engineer the tape contents to see how the assembler worked and then roll my own 4040 flavour. Seeing that there are a number of enthusiasts with 8 mod 80 boxes in the UK, and elsewhere on the planet, having the actual assembler would complete their systems. A unified request to the museum might help. Any information gleaned from the tape would be shared as source code and a hex file.
Regarding hardware, I've built a 20mA current loop <> USB serial adapter to pretend to be a 33ASR, and a high-speed tape interface that uses an Arduino.
To aid writing the 4040 code I've coerced a Teensy 4.1 to emulate the intellec 4 mod 40 and execute 4040 code at the correct rate. A lightbulb moment arose when I realised that the Teensy could be made to emulate similar vintage intellecs, such as those withe 8008 and 8080 processors.
If anybody has any thoughts on where to look for original paper tapes for these wonderful beasts, please get in contact!
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Old 27th Jun 2024, 11:52 am   #20
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Default Re: Intellec 8 Mod 80

Hello, and thanks for posting details on this (I've not seen an Intellec 4 before) - Plus welcome to the forum
You'll probably find your first few posts may take a short while to appear, while they get checked by moderators (to prevent spammers joining).

Although unfortunately I don't have an Intellec, I did acquire a 4040 chip set, so have been considering building a PE Champ etc to use it on.
And an original 4040 assembler would be of interest to me too.
I'll check the MCS-40 databook I got with the 4040 chip set, to see if Intel happened to include any source / hex listings in that.

Owen
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