At 11:00 pm 26/08/2001 +0100, Tony Duell wrote:
>>
>> Incidentally, if I ever get good at this stuff, I'll probably take a ROM
>> dump of my TRS-80 Model 102, and figure out how to update it into the 21st
>> century (i.e. replace a 19 with a 20), and give it a 100-year new lease of
>> life :)
>
>I must do that for the M100 sometime. It shouldn't be too hard to do.
Apparently, there is an all-software patch; although I've not investigated
it very far. It is, however, susceptible to corruption from BASIC, the
memory it resides in being non-protectable.
>Fortunately neither machine does an automatic day-of-week calculation
>(you have to set DAY$ by hand), so the issue is just changing the 19 to
>20 on the main menu, etc. Not hard to do
Yup. In fact, the main issue would be finding the right "19" to change...
>> More or less what's happening with me now.... Except i don't have a
>> mainframe to play with, or indeed the space to keep a mainframe in....
>
>The P850 is a mini, not a mainframe. It's just 1 10.5" high rackmount
>chassis. Not that large (I find rackmount machines take up less space
>than home micros, if only because you can stack them. The 'silly' cases
>many micros are in with absolutely no right angles, and a top that slopes
>in all direactions are impossible to stack things on top of...
Very true... I think I could squeeze one rackmount in here, although access
to it would be very difficult.
>
>I have a lot of the older HP calculator manals and program libraries,
>too. Some of those programs are works of art. And FWIW, I have no
>intention of using VB for anything...
Well, it's useful for some things. Like earning me a stack of cash for the
last 8 years :)
>As I said the other day, I don't see the point of a calculator emulator
>(if I have a powerful enough computer to run the emulator, why not just
>solve the problem using it, without slowing it down by making it emulate
>some other machine). But I most certainly do see the point in preserving
>old calculators (particularly programmable ones) and using them to run
>such programs.
There is that. Also, no emulator could emulate those horrible clicky keys
Sinclair used...
OTOH, it would be an interesting thing to do (if not use), just to try to
figure out how it all hung together.
[Hysteresis]
>>
>> I had to go look "hysteresis" up... Still not 100% sure where/why that
>> would be useful...
>
>OK, you want to make a striking clock. At the hour, you have to release
>the stricking mechanism, which then operates the bell hammer the
>appropriate number of times, and then shuts down.
<snip explanation>
Thanks!
>This idea works (and is used) in electronic circuits which need to be
>triggered on edges of pulses rather than levels, too. I've used it myself
>(an electronic state machine built from a D-type and a couple of gates)
>several times.
Ah - In fact, reading up on the replacement 6502, it mentions
edge-triggered functions.
>> [GPIB]
>>
>> >I'm pretty sure some HP 9000-series Unix boxes have HPIB disks, BTW...
>>
>> Blimey. I wonder if they'd work on a PET...?
>
>They'll plug in OK (and the magic smoke won't come out) but the command
>sets are totally different. So LOAD and SAVE won't do the right thing. If
>you want to write your own drivers it should be possible...
:) A project for another day, perhaps...
>> It could be the cost thing - AFAIR RS were always more expensive than
>> Maplin, so (naturally) the school had Maplin catalogues and not RS (or
>
>As I keep on saying, my time (and insanity) is worth a lot more than the
>minor diffeenve in price between RS and Maplin (in any case, Maplin are
>not cheap any more...)
Agreed - but it would be of more consequence to a schoolkid having to buy
stuff. I'd also prefer well stocked to "cheapest"; it sounds like RS fit
that bill.
>[Maplin]
>> Pretty much the same here, although I have to go all the way out to Marble
>> Arch... I could go to Stratford, which is probably nearer, but invloves a
>
>I've only ever been to the Marble Arch shop once, and it seemed to be
>very small and badly stocked. If I am in that area, I normally try
>Henry's Radio (as was, now Henry's Audio Electronics), 404 Edgeware Road.
Cheers, I'll give them a look in next time I'm over there.
>
>> drive; not something I like to do when the shops are open (too damn busy).
>
>How near is it to the Tube station? Isn't the Holborn shop nearer than
>Marble Arch?
Probably, but it's always shut when I find I need something...
>> >A lathe becomes useful when you have other, related, hobbies like model
>> >engineering.
>>
>> :) I'm deliberately trying to keep my number of hobbies (especially
>> expensive ones) down; motor racing takes up a *lot* of space, time & money;
>
>You know, I'd have thought a lathe was essential for hackish motor
>racing. To make things like bushes, spacers, special tools, and so on...
Not really - my car uses mostly stock components, so no special machining
is required. For things like cam grinds, etc., it goes back to the engine
man - who does have all that sort of stuff.
I just drive it (rather badly, at that).
>[Connectors]
>> True... I've used plug-block extensively in the past, largely because it
>
>To me a 'plug block' is one of those infernal solderless breadboards that
>you stick ICs and other components into.
Ah - I must mean "chocolate block", as described below. I've *never* used
that sort of plug-block, veroboard was the closest thing to it I ever used.
>Do you perhaps mean 'chocolate block' -- those screw terminal strips. I
>don't like those much for in-line connectors that I am going to want to
>disconnect and reconnect because you need to use a screwdriver to remove
>and reconnect the wires. And the wires are not kept in sequence when removed.
I had one block (about 20 wide) which *could* be plugged/unplugged
properly, as it consisted of two parts. I've used it all, however, and not
bought/found any more since.
>> [PIC]
>> >
>> >If you want to make a processor from TTL chips, or from discrete
>> >transistors, or even from valves, well, that's a reasonable thing to want
>> >to do. It's going to be slower than many microprocessors you can buy now
>> >[1], but that's probably not the point. You can't fail to learn a lot
>> >about procesor design by making one.
>>
>> :) Can you *really* see me soldering hundreds of transistors onto a PCB? I
>
>Yes!
Hmm. Maybe I ought to post up a picture of my workspace.... "Big" is not
the first word that would spring to mind.... Mind you, I'm probably going
to be moving come next year, hopefully to somewhere significantly bigger,
which will leave room for this sort of thing. Incidentally, by lack of
room, I mean I have free work surface of about 8"x14"; unless I go to the
kitchen...
[Bistables/Flipflops]
>
>A bistable (as in an Eccles-Jordan circuit [1]) can be built from just about
>any 2 active devices (triodes, transistors, FETs, even relays).
>
>But to make a useful flip-flop you need 4 transistors (2 for the
>bistable, 2 for input switching). HP used 4-transistor JK flip-flops in
>the HP9100, for example (and if there'd been a simpler way they would
>have used it)
>
>[1] Another old idea. The Eccles Jordan paper was published in 1919 IIRC.
Hmm. I *have* got some learning to do...
My electronics books should be here by Tuesday though :)
>> >> Eek - self modifying code? Dangerous....
>> >
>> >You mean you _don't_ write self-modifying code? Odd....
>>
>> It was drilled into me from a very early age that self-modifying code was A
>> Bad Thing.
>
>As I said, I am not a programmer, so I don't worry about such things.
:) It plays havoc with your designs.... Imagine a circuit that could
reconfigure itself at will...
[DM displays]
>Probably. New dot-matrix displays are not cheap, and surplus ones, while
>they normally work fine are not the sort of thing you can depend on still
>being available in a few months time...
Maybe I'll just build a teletype... It should be possible to convert a
typewriter ;)
>Since you're getting a 'scope, you could try making a vector display (a
>couple of DACs driving the 'scope in X-Y mode). Or you can make a 40*25
>text display in about 3 chips (all of them easy to obtain) that will
>drive the RGB inputs on a normal TV set.
Actually, that sounds much more promising...
Cheers!
Ade.
--
B-Racing: B where it's at :-)
http://www.b-racing.co.uk
Received on Sun Aug 26 2001 - 19:10:34 BST