On Wed, 24 Nov 2004, Tony Duell wrote: Really? My neighbors often discard computers, although admittedly rarely laptops. They HARDLY EVER discard a handful of buffer chips (or discretes). Therefore, the computer is cheaper and easier to obtain than components. 'Course I could get components by taking apart the discarded computers, but I seem to recall that you didn't approve of rendering working machines inoperable to get parts. Couldn't you flash the lights using a discarded computer? Remember that 25 DEC == 31 OCT, which is the day of an American rowdy holiday just before your Guy Fawke's day. -- Grumpy Ol' Fred cisin(a)xenosoft.com

In message <20041124154031.Q41898(a)shell.lmi.net> Fred Cisin <cisin(a)xenosoft.com> wrote: I've had the same experience - Them> "Would you like this computer?" Me> "What is it?" Them> "Um.. 386-25 with 1MB of RAM" Me> "To tell the truth, I don't collect PCs, they're not that rare, or even particularly useful." Them> "Oh, OK. I've got a ZX81 you can have for fifty quid. Or a C64 for ?95" Them> "They're going in the bin tomorrow, so let me know before then, ok?" See my point? Agreed. I've got, what, three PC laptops and two Acorn A4s. The lowest-spec PC laptop has been earmarked for testing various bits of hardware, the A4s are used roughly once in a blue moon (one needs a new floppy drive, though). So far the most I've hooked up to the high-spec (relatively speaking) PC laptop is an Ethernet card and the EPROM programmer. I wouldn't object to ripping PCs apart - again, common as dirt. I would cringe at the sight of someone ripping apart a perfectly good ZX81, and if someone dared destroy an Acorn System-1 (or anything of a similar rarity or vintage), I'd probably offer the owner a few quid and buy the machine before they nuked it. They get beer money, I get some more historical computer gear to preserve. Current rarest machine: a Jupiter Ace that needs major motherboard repairs. Assuming I can get the m/b back that is :) If anyone's got a Jupiter Ace that they want rid of, I'm listening :). Same applies to MOS KIMs, Synertek SYMs/SY-VIMs, Rockwell AIM65s, that sort of thing. Speaking of which, iirc someone offered me a SYM-1 a while back.. they wanted somewhere in the region of $900 for it. Last I heard, it hit the dumpster. Real shame - then again, their property, their choice :-/ Later. -- Phil. | Acorn Risc PC600 Mk3, SA202, 64MB, 6GB, philpem(a)philpem.me.uk | ViewFinder, 10BaseT Ethernet, 2-slice, http://www.philpem.me.uk/ | 48xCD, ARCINv6c IDE, SCSI ... Smash forehead against keyboard to continue...

I don;'t have a single PC-compatible laptop. I've got a Tandy M100, a handful of Epson HX20s and a PX4, an HP110 and a couple of Portable Pluses..... I do use them, but I don't think any are particularly suitable for making a KM11 clone. Incidentally, if you use a laptop to make a KM11 clone, presumably you need some hardware to link it to the KM11 slot on the DEC backplane. I can't believe that's the sort of thing that's thrown out by your neighbour (or, indeed, is as easy and cheap to obtain as a few buffer chips). What's this love of the ZX81, which I regard as a postively horrible machine. I'd not rip one apart, though, mainly because there's little of use to raid from it... I've only got one, and I'm hanging on to it. I happen to like Forth (and RPN in general). -tony

On Thu, 25 Nov 2004, Tony Duell wrote: I used a Sinclair for years as a doorstop. I much prefer wedge type doorstops over boat anchor style (such as monitors, printers, or XTs). But one day, somebody WANTED it. So, I traded the Sinclair to him for a rubber wedge doorstop. THe rubber wedge doesn't work anywhere near as well as the Sinclair, but the trade made somebody very happy.

Hi, Tony Duell said: I can combine both of those :-) I have a ZX81 that runs Forth[1] from an EPROM. Unfortunately I have no way of reading the eprom to make a copy, and it's a commercial copyrighted product anyway. Perhaps if I could locate the author he'd make it freely available, after all there can't be many Forth fans with ZX81s these days! My ZX81 is in a big box with plug-in cards and a keyswitch keyboard... [1] Skywave multi-tasking windowing Forth. -- Cheers, Stan Barr stanb(a)dial.pipex.com The future was never like this!

Hi, Tony Duell said: That's the one... All the normal Forth words including C! and C@ etc are there... It's a fairly full featured Forth, it just runs out of the eprom which replaces the ZX81 one, rather than a program that loads on top of the ZX81 system. Blocks on cassette are a difficult thing to cope with though! It would be nice to make a copy eprom though, just in case. Writing it out to cassette would be possible, but a bit tedious, an eprom burner is the answer I think... At the time it was very impressive to see multiple applications running simlutaneously in (tiled) windows on a ZX81, come the think of it it's still quite a feat. (I have Forth on just about every machine here, from Mac to PDP-11...) -- Cheers, Stan Barr stanb(a)dial.pipex.com The future was never like this!

Hi, Glen Goodwin said: A bus extender with two in/out cards (8255 based, three 8-bit ports each) and a 16K RAMpack. 2 of the i/o ports were used with a 2-port 8-bit analogue to digital input board. I'll try. My old Apple Quicktake 100 (on-topic now?) won't focus close enough but I plan to get a new camera for Xmas... (Most of my photography is black'n'white using older cmaeras!) -- Cheers, Stan Barr stanb(a)dial.pipex.com The future was never like this!

----- Original Message ----- From: Tony Duell <ard(a)p850ug1.demon.co.uk> You regard it as horrible because . . . ? (Please don't mention the keyboard. Lots of machines of that era had crap keyboards. It's easy to attach a better keyboard to a ZX81.) Glen 0/0

On Sat, 27 Nov 2004, Cameron Kaiser wrote: Oh it's a totally horrible machine -- that's why it's so great! It's pretty damn minimal, I recall my brother's '81 (kit) did some bad display glitch when it had to think really hard. It did a lot with little hardware. Not my cup of tea, but I can see how it's someone elses. Hell I drive Ramblers and AMC cars, no one likes them either. People in glass houses, something about stones. (BTW, I'm allegedly going to be on the History Channel's FULL THROTTLE TV show... 19 Dec... I'm the AMC/Rambler expert for one of those monster-garage type shows. I have NO IDEA what it's gonna look like...)

Ron Hudson wrote: RND should return a number between 0 and 0.999<whatever> Gordon

On Sat, 2004-11-27 at 18:27 -0800, Ron Hudson wrote: Just rnd I think, no parameters, brackets etc. - 'let x=rnd' should work. That 'for' syntax looks right too. Hmm, the BASIC *might* be picky about spaces btw. cheers Jules

OK, in no particular order : The keyboard (and see below for my comment on your comment). It's almost unusuable The video system. It's a total kludge, about the worst I've seen The cassette storage (I am used to _reliable_ data storage systems) The BASIC. BASIC is not my favourite language at the best of times, this versions is one of the worst, though The expansion connector (the physical form of it, the fact that if the RAMpack wobbles, the machine crashes). The ULA. I dislike hardware I can't hack, modify or repair. OK, most of those can be got round by adding/replacing hardware. But by the time you've finished, about all that's left of the ZX81 is the Z80 CPU, and there are plenty of easier ways of getting and useing that chip. For the time, it was cheap, and therefore sold well. Nowadays there are many, many, nicer machines available for less money than a second-hand ZX81... -tony

Multiple replies below. ----- Original Message ----- From: Witchy &lt;witchy(a)binarydinosaurs.co.uk&gt; Thanks, Adrian -- that's exactly the case for me as well. Every penny of my income since 1986 is directly attributable to the fact that I learned to program on a TS/1000. ----- Original Message ----- From: Cameron Kaiser &lt;spectre(a)floodgap.com&gt; me a a My thanks to you, too, Cameron. It *is* hackable, it *is* facinating, and -- how many years has it been since I sent you that thing? ;-) ----- Original Message ----- From: Dave Dunfield &lt;dave04a(a)dunfield.com&gt; Well, yeah, but when you consider that there isn't any video circuitry . . . Can't deny that. display. One transistor + one resistor + one monitor = rock solid display. problems/flakiness to Scraps from the junk box and 30 minutes time will yield a cable which provides enough distance from the ZX81 to eliminate the "wobble" problem. Odd but highly functional. essential a Personal preference. But, traditional SUPPOSED to be It is minimalism in the extreme. bought it Whereas I got much more than my money's worth out of it, since the learning experience which began with my ZX81 continues to this day. ----- Original Message ----- From: Tony Duell &lt;ard(a)p850ug1.demon.co.uk&gt; An extremely clever design, wouldn't you say? Many inexpensive machines of the day used cassette storage. Several software solutions were developed which increased both the reliability and speed of ZX81 cassette i/o (from 300 to 4800 baud). Lots of great Z80 assemblers out there. See reference to junk box above. Granted. The ULA is truly a black box. Umm, considering that you can easily buy a ZX81 for US$10 (if you can't find one for free) . . . Lots of people today use them for robotics controllers and other "down and dirty" applications where no frills are required. With the onboard BASIC and easy access to the Z80 bus, it makes sense. Thanks to all for a pleasant discussion. Glen 0/0

Jim Brain wrote: From memory, desolder the resistor inside the UHF modulator that goes to the middle pin of the phono. Poke one lead of a 75 ohm (or thereabouts, 68 is common and close enough) through the polythene through the polythene bush, and solder it to the socket instead. Solder the emitter of a small NPN tranny to the other end. Solder the base of the tranny to the video lead, the other one that goes through the bush, and solder the collector to the +5 supply where it goes into the feedthrough cap. Finally solder another 75 ohm resistor between the junction of the first one and the emitter, and ground. You may need to adjust those values, I may be wrong. Get a 2x23 edge connector, a bit of circuit board etched and shaped to match the edge connector on the ZX81, and a bit of ribbon cable. Wire them together. Gordon.

Not over here they don't... I've just looked at my KM11 clone. It's got 6 chips in it. 4 ULN2003's (pr 2803s, not using one secion of each), a 7400 and a 7406. It would be easier for me to find those than to find any computer... It wouls also probably be cheaper for me to buy those chips than to get the necessary software for the computer. Even if it's all open-source, including the OS, I'd still have to download it. Then there's the issue of where the heck do I put another computer, how do I set it up near the DEC machine I'm tryign to repair (my KM11 clone is in a small plastic box, much smaller than a laptop), the fact that the physical toggle swithces are a lot easier tha using a mouse (and finding somewhere to use it near the PDP...) and so on. And FWIW I have been given several large bags/boxes of new ICs, transistors, etc that were going to be thrown out... PCs don't count ;-). I did. I've got a set of Newtonsday lights controlled by a PERQ 2 T4.... Now that _is_ overkill.... Indeed. Newtonseday is much the same as Halloween.... -tony