7400 series logic availability

[rob77]

Building an 8 bit computer using 74xxx chips is a walk in the park compared to the MegaProcessor:
 
  http://megaprocessor.com/index.html

In either case these projects are a personal journey and who are we to say they shouldn't be attempting it.

that's ultra cool actually one of my childhood dreams was to build a processor from discrete transistors.. but when i was young i had no money for such a project, later i had no time for that and now, when i could spare the money and also the time.... i'm not interested in the idea anymore (shame on me for that !)  

[tszaboo]

Building an 8 bit computer using 74xxx chips is a walk in the park compared to the MegaProcessor:
 
  http://megaprocessor.com/index.html

In either case these projects are a personal journey and who are we to say they shouldn't be attempting it.

Someone should make a processor like that from IGBTs operating at 1000V.

[tggzzz]

Building an 8 bit computer using 74xxx chips is a walk in the park compared to the MegaProcessor:
 
  http://megaprocessor.com/index.html

In either case these projects are a personal journey and who are we to say they shouldn't be attempting it.

Someone should make a processor like that from IGBTs operating at 1000V.

Personally I'd start with dekatrons; it is well worth going to see the world's oldest operating computer: https://en.wikipedia.org/wiki/Harwell_computer

It also saves wiring up front panel LEDs

[rob77]

Someone should make a processor like that from IGBTs operating at 1000V.

1kV logic would be quite immune to noise... even during heavy lightning hitting the computer itself unfortunately it would be immune to high clock frequencies as well  and the performace would be measured in FLOPMs - floating point operations per month

[tggzzz]

Someone should make a processor like that from IGBTs operating at 1000V.

1kV logic would be quite immune to noise... even during heavy lightning hitting the computer itself unfortunately it would be immune to high clock frequencies as well  and the performace would be measured in FLOPMs - floating point operations per month

The first commercial computer I used, an Elliott 803, had a very well regarded Algol-60 compiler, 39bit words and a fastest cycle time of 575us. Yup, 2kIPS.

It played music, but the higher notes were distinctly flat You can see/hear one operating here: http://www.tnmoc.org/

If you ask nicely, they will get out the circuit diagrams and discuss them with you. Yes, I have considered recasting the primitive blocks into an FPGA

[Tom45]

Someone should make a processor like that from IGBTs operating at 1000V.

The first step in the project would be to make sure your life insurance was paid up. 

[Tom45]

The first commercial computer I used, an Elliott 803, had a very well regarded Algol-60 compiler, 39bit words and a fastest cycle time of 575us. Yup, 2kIPS.

It played music, but the higher notes were distinctly flat You can see/hear one operating here: http://www.tnmoc.org/

If you ask nicely, they will get out the circuit diagrams and discuss them with you. Yes, I have considered recasting the primitive blocks into an FPGA

I learned programming on an Alwac 3e, a tube and drum computer with a 5ms cycle time, an order of magnitude slower than your Elliot 803. 200 ips!

I've always wanted to visit Bletchley Park, but hadn't heard of the National Museum of Computing until seeing your link to it. Now I have one more reason to visit. Thanks.

[tggzzz]

I've always wanted to visit Bletchley Park, but hadn't heard of the National Museum of Computing until seeing your link to it. Now I have one more reason to visit. Thanks.

There was an acrimonious split between the Bletchley Park Museum and TNMoC a few years ago.

I haven't been to Bletchley Park Museum, and only been to TNMoC once. However, I intend to return to TNMoC since the museum staff are the best I have seen in any museum: they have personal experience of the exhibits and will discuss them in detail. Highly recommended.

The only bad thing is that I remember using many of the exhibits

[james_s]

The only bad thing is that I remember using many of the exhibits

That's fascinating though, I mean getting old sucks, but for those of us who were not around when some of the really influential old stuff was in active use it's interesting to hear from those who were.

[tggzzz]

The only bad thing is that I remember using many of the exhibits

That's fascinating though, I mean getting old sucks,

It is usually better than the alternative

but for those of us who were not around when some of the really influential old stuff was in active use it's interesting to hear from those who were.

I used the Elliott 803 while I was at school; it was more or less a museum piece then! I did meet the author of the Algol-60 compiler, CAR Hoare, in the 90s, though.

Quite a few of the TNMoC exhibits are from the 70s/80s. The oldest computer I own is a "Fat Mac" - which I used to learn OOP with Smalltalk.

[james_s]

I was fascinated to discover that one of the older guys I work with wrote part of the operating system for the Atari ST back in the 80s. That was an exciting time to work with computers, technological development improving by leaps and bounds, amazing new features and capabilities coming out all the time, hardware and software becoming more powerful at a crazy pace. Better graphics, better sound, faster, smoother, higher resolution, more memory, it just kept getting better and better. Then at some point it plateaued, computers got boring, new versions of software started to occasionally be worse than the version they were meant to replace, then that became increasingly common. Now I can't think of anything I do with my computer that I couldn't do nearly as well a decade ago. The array of different platforms is gone, no more Amiga, ST, drooling over Sun and SGI workstations, these days you can get a PC or a Mac, which is essentially the same, it's just not exciting anymore.

[tggzzz]

I was fascinated to discover that one of the older guys I work with wrote part of the operating system for the Atari ST back in the 80s. That was an exciting time to work with computers, technological development improving by leaps and bounds, amazing new features and capabilities coming out all the time, hardware and software becoming more powerful at a crazy pace. Better graphics, better sound, faster, smoother, higher resolution, more memory, it just kept getting better and better. Then at some point it plateaued, computers got boring, new versions of software started to occasionally be worse than the version they were meant to replace, then that became increasingly common. Now I can't think of anything I do with my computer that I couldn't do nearly as well a decade ago. The array of different platforms is gone, no more Amiga, ST, drooling over Sun and SGI workstations, these days you can get a PC or a Mac, which is essentially the same, it's just not exciting anymore.

Agreed. Back then there was  a "pre-cambrian explosion" centered on micros. Nowadays the nearest equivalent centre on additive printing, manpower electronics, and applications enabled by very high speed ADCs/DACs. If I was starting again , I would go into genetic engineering.

[Tom45]

I used the Elliott 803 while I was at school; it was more or less a museum piece then! I did meet the author of the Algol-60 compiler, CAR Hoare, in the 90s, though.

That's cool that you got to meet Sir Tony Hoare. His early claim to fame was developing QuickSort in 1959.

[ebastler]

Nothing wrong with building a retro design (in my book, at least).  If you have a retro circuit diagram which calls for 74189s, I would definitely try and use these. Simulating in FPGA is just wrong! 

I'm wondering whether there has ever been a 74HC189; probably this small RAM capacity was obsolete by the time the HC series became popular. But you can easily obtain old 74LS189 chips, through ebay etc..

The output of an LS TTL IC does not reliably drive a HC input (which has a switching threshold of 2.5V). So you can't simply mix and match LS and HC series in one circuit. But if you use HCT chips as the interface between them, you'll be alright: These have an input threshold matching the old LS series outputs, and provide full 5V output to match the HC series.

So you could either move your complete circuit to HCT (and some LS where needed) -- not necessarily recommended, since the noise immunity will not be as good as with HC signal levels. Or you can connect HCT chips to all the 74LS189's outputs, and use HC series chips everywhere else.

[tggzzz]

Nothing wrong with building a retro design (in my book, at least).  ..... Simulating in FPGA is just wrong! 

Well,... yes but.

I'd half-tempted to recreate an Elliott 803 in an FPGA, just as someone has recreated a Cray-1 in one.

But I'm certainly not tempted to find all the ferrite cores used in the logic gates, nor to fill up two rooms of my house. Plus I've only got one small plane of ferrite core memory, not the double shoebox of 8192*39 (no misprint) necessary for a fully-loaded machine.

[Moshly]

Building an 8 bit computer using 74xxx chips is a walk in the park compared to the MegaProcessor:
 
  http://megaprocessor.com/index.html

In either case these projects are a personal journey and who are we to say they shouldn't be attempting it.

Someone should make a processor like that from IGBTs operating at 1000V.

Personally I'd start with dekatrons; it is well worth going to see the world's oldest operating computer: https://en.wikipedia.org/wiki/Harwell_computer

It also saves wiring up front panel LEDs

Not retro enough, how about going EM with ->
http://web.cecs.pdx.edu/~harry/Relay/

Or, how about just M ->

[tggzzz]

Building an 8 bit computer using 74xxx chips is a walk in the park compared to the MegaProcessor:
 
  http://megaprocessor.com/index.html

In either case these projects are a personal journey and who are we to say they shouldn't be attempting it.

Someone should make a processor like that from IGBTs operating at 1000V.

Personally I'd start with dekatrons; it is well worth going to see the world's oldest operating computer: https://en.wikipedia.org/wiki/Harwell_computer

It also saves wiring up front panel LEDs

Not retro enough, how about going EM with ->
http://web.cecs.pdx.edu/~harry/Relay/

Or, how about just M ->

I think I'll stick with my earlier (almost) infinitely parallel computer.

[Nusa]

This is a pet project to build an 8 bit computer from 7400 series logic. 

That's something I actually did once, as part of a Computer Science lab. Of course, it was the 1970's and 7400 series logic was fully available. Wirewrap sockets, spool of wire, hand wirewrap tool, net lists, logic probes to verify. Ended up with a single-board PDP-8 with idiot lights and toggle switches plus a UART for connecting to one of the TTY's in the room. The professor who taught that version of the class, Dave Winkel, passed away last year. One of my Dad's friends.

[james_s]

I've always wanted to build a computer proper 70s style on a big FR4 prototype board using wire wrap, maybe a 6502 or Z80. Wire wrap sockets and pins are quite expensive though.

[brucehoult]

I've always wanted to build a computer proper 70s style on a big FR4 prototype board using wire wrap, maybe a 6502 or Z80. Wire wrap sockets and pins are quite expensive though.

Some friends and I built a wire-wrapped 6809 computer in 1983. I think the 6809 was a bit more of a single-chip solution than many previous chips. I recall 8 x 64 kbit DRAM, a ROM, a UART, and some kind of interface to a couple of 8" floppy drives salvaged from somewhere. I was quite proud of my clock circuit which ran the CPU at different speeds depending on what it was talking to ... the RAM was happy at 2 MHz. The ROM claimed to be a 1 MHz part but close examination of the timing diagram showed that actually it should be happy with an asymmetric clock with 0.5 us high and 0.25 us low (or vice versa) for effectively 1.33 MHz, so I implemented that. It worked :-) I think some other parts wanted a real 1 MHz. The state diagram was not that tricky.

We debugged the thing and got it going in about two hours using nothing more than a dual trace CRT oscilloscope. There were two bugs: 1) the reset switch was wired NC instead of NO; 2) the UART clock divider got wired as divide-by-12 when it needed to be divide-by-13 to get a 9600 bps x16 clock to it from the 2 MHz system clock (or maybe it was 19200 x8 or 38400 x4 .. I don't remember now).

Fun times.