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Old 16th Nov 2019, 4:16 pm   #21
Radio Wrangler
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Default 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)
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Old 16th Nov 2019, 4:28 pm   #22
Karen O
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Default 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!
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Old 16th Nov 2019, 6:32 pm   #23
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Default 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.

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Old 16th Nov 2019, 6:40 pm   #24
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Default 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.
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Old 18th Nov 2019, 12:32 pm   #25
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Default 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.
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Old 18th Nov 2019, 2:16 pm   #26
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Default Re: Computer retro homebrew: Orton ZX79

Quote:
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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.
It more or less still exists under the XMOS/xCore name:
https://www.xmos.com/

Chris
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Old 18th Nov 2019, 9:41 pm   #27
Karen O
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Default 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.
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Old 19th Nov 2019, 5:48 am   #28
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Default 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.
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Old 19th Nov 2019, 11:56 am   #29
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Default 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
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Old 19th Nov 2019, 12:32 pm   #30
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Default 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
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Old 19th Nov 2019, 3:00 pm   #31
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Default Re: Computer retro homebrew: Orton ZX79

Quote:
Originally Posted by Karen O View Post
I used enamelled copper wire. Modern enamel burns off after application of the iron for a few seconds.
Recently I did a S-100 computer light pen project. It is in the vintage computer section.

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.
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Old 4th Dec 2019, 1:17 am   #32
Karen O
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Default Re: Computer retro homebrew: Orton ZX79

Here's my write-up for those who are interested.
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File Type: pdf Orton ZX79 computer manual.pdf (350.3 KB, 159 views)
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Old 4th Dec 2019, 5:38 am   #33
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Default Re: Computer retro homebrew: Orton ZX79

Excellent write up Karen. I wish I was smart enough to understand it!
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Old 4th Dec 2019, 8:05 pm   #34
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Default 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.
 
Old 4th Dec 2019, 9:24 pm   #35
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Default Re: Computer retro homebrew: Orton ZX79

Hear hear!

D
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