EDUC-8 Australia's First TTL Computer

[Steven Pietrobon]

G'day Everyone,

Just saw Dave Jone's video on the Gigatron TTL computer, so I thought people might be interested in a TTL computer from 1974, Electronic Australia's EDUC-8. Its an 8-bit machine with 256 bytes of RAM, based on the 12-bit PDP-8. It uses 100 TTL chips, so quite a bit more complex than the Gigatron. Unlike the Gigatron, you can program it directly, so it is a lot more fun to play with. If you're interested, check out my blog of how I built it at the link below.

http://www.sworld.com.au/steven/educ-8/

There's also an excellent emulator at the link below.

http://www.teenix.org/educ8.html

[georges80]

Back in oz I have the original educ-8 'magazine' - the one that encompasses all the magazine articles into a single document.

I was quite a bit along with the educ-8 component collection (back in '74) and then I went to uni and the 8080A was released and I ditched my plans to build a 16 bit version of educ-8 and figured something with a parallel data path and very rich (in comparison) instruction set would be a better bet. But the educ-8 articles certainly opened my eyes to processor architecture, ram, paper tape, printers, keyboards etc.

Spent most of that first year building a home brew 8080A system with front panel switches and LEDs.

Got lots of ideas from the educ-8 in terms of parallel i/o ports etc.

The golden years of home brew computing.

cheers,
george.

[wilfred]

@Steven Pietrobon  Nice work that. Although to be honest I have read your blog several times before.

It seems so primitive now but I can imagine that in 1974 it was still primitive  but would have been quite an exciting platform to learn about computers.

Can you attach some of the photos here. The links now require some form of login and I remember that wasn't the case.

I used to think it a stroke of bad luck that the EDUC8 was pipped by a month by the Mark-8 in an American magazine but I have since found out there was a design published in the Dutch Elektor in 1974 called computer-74. So There may be even more around that time in other non English speaking countries.

One thing I find interesting is that the EDUC8 was a bit-serial design where the bytes were serially clocked around much like the very early vacuum tube designs like CSIRAC. And even though the MARK-8 used the 8008 microprocessor chip I have only in the past year learned that the 8008 also started out as a serial TTL design in the Datapoint 2002  terminal. Intel and Texas Instruments couldn't make this chip operate fast enough or cheap enough for the clients needs so they went with a TTL design initially.

I posted a scanned cover of the EDUC8 with Jim Rowe from 1974 yesterday. Maybe it isn't a complete coincidence you posted.
https://www.eevblog.com/forum/eevdiscover/suggestion-for-eevdiscover-videos/msg1711151/#msg1711151

If  it isn't possible possible to get Jim Rowe and his original prototype together for a video  then you and your EDUC-8 together with Jim Rowe would be pretty good. As I was doing a bit of housekeeping here I noticed I have been asking for that for 5 years. I initially thought the 40th anniversary would have been an opportune time.

I wonder if there are other EDUC8's out there.   

Anyway thanks for joining up and sharing.

PS. There is a vintage computing section on this forum you may like to use in future.

[Steven Pietrobon]

G'day Wilfred,

I fixed the links to all the photos. You might need to reload the page to get the new links to work.

Its a complete coincidence that you posted that cover yesterday!

I've been thinking about doing a video of the EDUC-8. I have a flashy digital camera that also does video, but I haven't yet installed the software for it!

At the end of my blog are pictures of other EDUC-8's.

[intabits]

I built one of these back in 1974-6. It was pretty flakey, I think mostly due to the lack of gold fingers on the PCBs.

Being serial, and slow, the demands on the RAM chip were quite gentle. Yet Jim Rowe (the designer) specified an expensive ($50 in 1974) high speed Fairchild bipolar RAM chip.
This was a massive overkill, to which I baulked, and fitted $3 mos rams, (I think I used 2x2102 chips). They had a different pinout, but worked fine once bodged onto the PCB.

[Steven Pietrobon]

I built one of these back in 1974-6. It was pretty flakey, I think mostly due to the lack of gold fingers on the PCBs.

Yes, you definitely need to gold plate the edge connector pads. I heard similar of stories of EDUC-8's where this hadn't been done, so I went to the extra trouble of having the edge connector pads of my boards gold plated. I've had no reliability issues, with the computer still working perfectly after 10 years.

Being serial, and slow, the demands on the RAM chip were quite gentle. Yet Jim Rowe (the designer) specified an expensive ($50 in 1974) high speed Fairchild bipolar RAM chip.
This was a massive overkill, to which I baulked, and fitted $3 mos rams, (I think I used 2x2102 chips). They had a different pinout, but worked fine once bodged onto the PCB.

Yes, Jim went to the trouble of avoiding an expensive microprocessor, only then to go ahead and use expensive RAM! MOS equivalents of the 93415 later became available (the Intel 2115), which is what I used in my EDUC-8.

[intabits]

If I was ever to do this again (definitely not!), I'd bodge the artworks to use maybe arduino style headers and sockets instead of edge connectors.

But I don't need to do that as I have 2 *real* PDP8 computers (the inspiration for EDUC-8), and 3 PDP11s.
The PDP8/f and the PDP11/05 have front panel toggle switches like EDUC-8,  while the other 3 have octal keypads.

But I think a much better retro project (been done i'm sure) would be a PDP clone with a front panel and blinkenlights, with an Arduino (or whatever) inside doing the emulation. There's a ton of software available to use on such a beast.

Or maybe even an IBM7094 "big iron" front panel with a port of my emulator running inside it. A useful amount of software available for that also.

[Steven Pietrobon]

But I think a much better retro project (been done i'm sure) would be a PDP clone with a front panel and blinkenlights, with an Arduino (or whatever) inside doing the emulation.

As you suspected, that has already been done, but using a Rasberry Pi. You can even buy a kit for this!

http://obsolescenceguaranteed.blogspot.com/2015/01/new-project-pdp-8i-replica.html

[Riccardo Macri]

Steven, in his latest video where he explores the stuff they need to get rid of at the Australian Computer Museum Warehouse, Dave explicitly mentions the possibility of an original EDUC-8 being there, here:

https://youtu.be/mK4M8dv4NNU?t=197

Would have made my day if he'd found it.

[wilfred]

Apparently the staff at EA annoyed Jim Rowe by calling it the E-duck-8. Even back in the day I saw it as educate. But then I saw a picture of a Lamborghini in an American motor magazine about the same time with IXLR8.

I'm also crossmatching my TTL collection with the parts list to see how far short I fall. I have some 161, 162, 163 and 165, guess which one I need. I have 2142L SRAM. Hmmm. I'd say I could go 90% of the way before shopping. But the ones I don't have might be harder to find.

I respect the reproduction of the original with sockets and multiple PCBs but I think I'd try for a double sided PCB and just feel a little dirty. I'll add this to my field-of-dreams.

[rrinker]

But I think a much better retro project (been done i'm sure) would be a PDP clone with a front panel and blinkenlights, with an Arduino (or whatever) inside doing the emulation.

As you suspected, that has already been done, but using a Rasberry Pi. You can even buy a kit for this!

http://obsolescenceguaranteed.blogspot.com/2015/01/new-project-pdp-8i-replica.html

 Why did I have to read this at work? I just wasted an hour reading through his various systems, and now I want the 11/70 kit - especially since it has RSX-11 in the software image. My first post-college job included working with a machine controlled by an 11/23 with RSX-11 as the OS, and a pair of RL02 drives. Programmed in FORTRAN. When received (second hand - the thing was already nearly 10 years old when we bought it), it was mostly a large and expensive hunk of scrap. But I was able to get the 11/23 up and running, and we scrounged a video terminal so I had 2 terminals the video display plus a DECWriter printer. That is one bit of nostalgia computing I would love to go back to, and despite plenty of other projects I really want that kit now to build one.

[iMo]

FYI: PDP-8 ported on a $15 FPGA board
http://retrobsd.org/viewtopic.php?t=37810
Fortran, Pascal, Basic, etc. inclusive.
Front panel and blinkenlights not wired for simplicity reasons
Here is the schematics, blinkenlight and switches not included, it fits into a DIL16 package (reprinted with kind permission):

[Steven Pietrobon]

Steven, in his latest video where he explores the stuff they need to get rid of at the Australian Computer Museum Warehouse, Dave explicitly mentions the possibility of an original EDUC-8 being there, here:

Their website only shows they have the booklet with all the articles and at least one of the PCB's (the connector board). Comments mention difficulty in finding 0.15" spacing edge connectors! I had the same problem, so I changed the spacing of the pins to 0.156" on my PCBs so that I could use available edge connectors, converting 36 way double sided connectors to 16 and 32 way single sided.

http://www.aceware.com.au/acms/ItemDetail.asp?lngItemId=68&

[EEVblog]

Steven, in his latest video where he explores the stuff they need to get rid of at the Australian Computer Museum Warehouse, Dave explicitly mentions the possibility of an original EDUC-8 being there, here:
https://youtu.be/mK4M8dv4NNU?t=197
Would have made my day if he'd found it.

I can only presume it was gone already, or it's in one of their other warehouses or in a prized possession collection somewhere.
But no one there seemed to have heard of it. I believe it's the original prototype.

[Steven Pietrobon]

Apparently the staff at EA annoyed Jim Rowe by calling it the E-duck-8. Even back in the day I saw it as educate.

I originally thought it was pronounced edook-ate! Didn't get the "educate" pronunciation until much later.

I'm also crossmatching my TTL collection with the parts list to see how far short I fall. I have some 161, 162, 163 and 165, guess which one I need. I have 2142L SRAM. Hmmm. I'd say I could go 90% of the way before shopping. But the ones I don't have might be harder to find.

You can get all of the required TTL chips from Unicorn Electronics http://www.unicornelectronics.com/ in the US. For the 9001 JK Flip Flop, I have some for sale, or you can use the equivalent 74105. The 2142L is a 1Kx4 RAM with common I/O. You would need to modify the design a bit to adapt it for the memory board. The design uses two 1Kx1 RAMs with separate I/O, and configures them as a 2Kx1 RAM, so you would need to use two 2142Ls to get the address space. Alternatively, you can use two 2115 1Kx1 RAMs, which is what I did. Checking Unicorn, they are out of 2115s, but they do have the 2125. Difference is that 2115 is open collector while 2125 is tristate. Checking the schematic, each RAM is only accessed one at a time, so should be safe to use. The 2115 or 93415 are also available on eBay.

I respect the reproduction of the original with sockets and multiple PCBs but I think I'd try for a double sided PCB and just feel a little dirty. I'll add this to my field-of-dreams.

An alternative solution is to use my single sided PCB layouts available from my website. You will need GSview http://pages.cs.wisc.edu/~ghost/gsview/ to view and print the files. The only difficulty there is making the connectors and gold plating the edge connector pads.

http://www.sworld.com.au/steven/educ-8/educ8_pcb.zip