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