|
Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
|
Thread Tools |
16th Nov 2019, 4:16 pm | #21 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,876
|
Re: Computer retro homebrew: Orton ZX79
Expansion? How about a T414 as a co-processor if you're feeling adventurous and feel like a real bus incompatibility task?
David (the stress pill wore off)
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
16th Nov 2019, 4:28 pm | #22 |
Rest in Peace
Join Date: Jul 2011
Location: Bridgnorth, Shropshire, UK.
Posts: 787
|
Re: Computer retro homebrew: Orton ZX79
Well David,
You are putting yourself to the fullest possible use, which is all a sentient being can ask for T414? Was that around in the 70s...? I recall a fad at uni where people interfaced calculator chips as maths co-processors. Saves you kilobytes of maths routines but boy were they slow! |
16th Nov 2019, 6:32 pm | #23 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,876
|
Re: Computer retro homebrew: Orton ZX79
Mid eighties. It was the Transputer. Now that's bus incompatibility!
I might have some 2901 bit slices somewhere. David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
16th Nov 2019, 6:40 pm | #24 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,208
|
Re: Computer retro homebrew: Orton ZX79
Actually, if you can find a C011 or C012 chip (Transputer link interface) it is dead easy to hang a T414 or any other transputer off just about any microprocessor bus.
|
18th Nov 2019, 12:32 pm | #25 |
Octode
Join Date: Jun 2013
Location: Huddersfield, West Yorkshire, UK.
Posts: 1,795
|
Re: Computer retro homebrew: Orton ZX79
Transputer.. now thats a word I have not heard for a long time....whatever happened to it ?? I think Thorn got involved and the "bean counters" decided it was too expensive.
__________________
Should get out more. Regards Wendy G8BZY |
18th Nov 2019, 2:16 pm | #26 | |
Nonode
Join Date: Oct 2008
Location: Warsaw, Poland and Cambridge, UK
Posts: 2,677
|
Re: Computer retro homebrew: Orton ZX79
Quote:
https://www.xmos.com/ Chris
__________________
What's going on in the workshop? http://martin-jones.com/ |
|
18th Nov 2019, 9:41 pm | #27 |
Rest in Peace
Join Date: Jul 2011
Location: Bridgnorth, Shropshire, UK.
Posts: 787
|
Re: Computer retro homebrew: Orton ZX79
I've been giving thought to language extensions and come up with the function LINE() which accepts a line number and returns its address in memory. This is useful for the $ operator which references a string in memory.
LINE() would be great for selecting from an array of strings in the program text e.g.: PRINT $LINE(N+150) You could do dangerous stuff like self-modifying code too. Yikes! Another thing I'd like is a function VAL() which applies the BASIC expression evaluator to a string. |
19th Nov 2019, 5:48 am | #28 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,208
|
Re: Computer retro homebrew: Orton ZX79
One version (at least) of HPL (a Hewlett-Packard language similar in concept to BASIC) had a statement that stored a string as a program line. And yes you could use it in a program. One use was to store an asignment statement which could later be executed (thus a workaround for not having VAL() or EVAL() (as BBC BASIC called it I think)) but of course you could do any self-modifying code tricks you wanted.
|
19th Nov 2019, 11:56 am | #29 |
Octode
Join Date: Nov 2004
Location: Hebden Bridge, West Yorkshire, UK.
Posts: 1,885
|
Re: Computer retro homebrew: Orton ZX79
I'm not sure about self-modifying code or the need for reading data (beyond READ/DATA) but EVAL is invaluable for certain things - a nice counterpart might be EXEC to actually execute a statement. I investigated doing this in my port of BBC Basic but it was non-trivial without clearing all the variables and subroutine stacks - However, a thing I've often wanted is something akin to setjmp/longjmp in C to allow a drop back to a main menu or loop - i.e. clear any call stacks for GOSUBs/PROCs but retain the variables and execute say a GOTO?
D |
19th Nov 2019, 12:32 pm | #30 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,876
|
Re: Computer retro homebrew: Orton ZX79
A DIY programming language made from all the best bits of several others? A sort of polyglot. With my sense of humour, I'd name it GOLYPLOT
David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
19th Nov 2019, 3:00 pm | #31 | |
No Longer a Member
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
|
Re: Computer retro homebrew: Orton ZX79
Quote:
Quite a few TTL IC's required wiring up. I used multi-colour teflon hookup wire. The trick is though , to avoid the Bird's Nest effect is to route the wires to mostly avoid the IC socket pins, photo attached. Also the wires are restrained to the pcb with other wire loops. If these precautions are not taken, a complex prototype board can get out of control very quickly and become horribly messy, like many of the hand wired logic boards you see photos of on the net where no care was taken routing the wires. |
|
4th Dec 2019, 1:17 am | #32 |
Rest in Peace
Join Date: Jul 2011
Location: Bridgnorth, Shropshire, UK.
Posts: 787
|
Re: Computer retro homebrew: Orton ZX79
Here's my write-up for those who are interested.
|
4th Dec 2019, 5:38 am | #33 |
Tetrode
Join Date: Mar 2010
Location: Monroe, Georgia, USA. (from Coventry, UK).
Posts: 77
|
Re: Computer retro homebrew: Orton ZX79
Excellent write up Karen. I wish I was smart enough to understand it!
|
4th Dec 2019, 8:05 pm | #34 |
Guest
Posts: n/a
|
Re: Computer retro homebrew: Orton ZX79
Very interesting and exhaustive, a proper write up and a joy to read (I do enjoy a good datasheet). Brings back memories of the Acorn Atom et al, proper computers that one could understand! I still have the basic memory map of the Atom in my head and a copy of "Atomic Theory and Practice" somewhere.
|
4th Dec 2019, 9:24 pm | #35 |
Octode
Join Date: Nov 2004
Location: Hebden Bridge, West Yorkshire, UK.
Posts: 1,885
|
Re: Computer retro homebrew: Orton ZX79
Hear hear!
D |