Adventures in old 80s computers.

[S. Heslop]

This might be a bit bizarre for this forum, but hopefully people will find interest in it. Also, as a disclaimer I'm not really very knowledgeable about these old computers, or computers in general. I only know as much as I can Google!

Currently i've been messing with an Atari 520ST-FM I found at a boot sale for a bargain.

First thing I had to make for it was a video cable to hook it up to an old LCD TV. This model of Atari ST has an RF out for use with TVs, but it gives pretty rubbish quality video. I'm using this diagram that I found with a quick Google search.


I shoved the 13 pin din connector into an eraser to prevent the pins from wandering when the plastic got soft from the heat. The pins didn't have solder cups and it was pretty tight getting everything soldered.


There was more space on the scart side, but it was even more of a fiddle making sure every cable went where it was supposed to.


See if you can spot the typical mistake.


The cable works!


For a while I was thinking that the floppy disk drive wasn't working since it was giving errors when I tried open an unformatted disk. I had the drive partially disassembled, cleaned, and put back together twice before I found the menu item (under the file tab) to format it. Doy! Glad I didn't go as far as replacing all the electrolytic capacitors before finding that.

After that I had to hook up the old Windows XP computer (it's funny to think it's more than 10 years old now) since it's the only one I've got that can still support a floppy drive.

At first I was trying to use the floppy image program to write disks but it was giving me no results. Disks were ending up corrupt at best, and crashing the Atari whenever I tried open them. Which after some reading might be due to the image files I was trying to write having more cylinders or sectors than a PC floppy drive can write reliably.



Then I tried using the Windows command prompt to format the drive (typing "format a: /t:80 /n:9", for 80 cylinders and 9 sectors) with tape over the right hand hole in the disk to fool the drive into thinking it's an older 720kb double density disk, rather than 1.44mb high density.



Then after simply copying files over in Windows explorer, like you would any other files...



It worked! I'm running a music demo that includes this tune. It's the first demo tune I ever heard. Honestly I'm a little bit embarrassed posting it, since it's fairly corny and limited music. But it's probably worth showing what kind of sound this system is famous for. There's music programs that can support low-fi samples but they take up too much CPU power to be too useful.

Unfortunately this only works for things released as regular folders. Alot of Atari ST programs seem to be distributed as .st and .msa image files that require that floppy image program to write them, so i'll need to figure out that whole thing at some point.






But with the Atari ST working it's now time to bring out the big guns. I've had these stored under the bed for a while now, the older 'breadbin' style Commodore 64 up top used to belong to my uncle, but it unfortunately doesn't work (but still has useable components). The C64C below was bought on ebay, along with a few accessories like a mouse adapter and a midi cartridge for controlling the audio from a newer computer.

What makes the C64 an interesting computer is it's famous 'SID' sound chip. It's more or less a little analogue synthesizer on a chip, complete with a filter. It was very advanced (and weird) for it's time, and is still well renowned for producing a great sound. On its own it's fairly limited, with just 3 oscillators and the single filter to share between them (that's not to say that it can't produce decent music on its own though!). But it has alot of potential as a musical instrument to accompany other stuff.

The only problem is that with 5 1/4" floppy disk drives, cables galore, a monitor, switches, and power adapters it's awkward to use and takes up way too much desk space. So the plan is to try make a single compact self-contained case for everything, with just a single power cable to worry about. First i'll have to measure and draw up the various boards.


As a side, check out these fantastic game covers.

[Pete49]

How to restore memories.  I still have a TRS 80 with tape drive and the ubiquitous C64 and don't have the heart to toss them out. I'll be watching this thread 
Pete

[rockknocker]

Great work! These old computers have a lot of character, and its nice to see them working again! I'll be following this project closely.

[DavidA]

I also have a few old computers. Still use them occasionally.

As for the mistake.  I've done it with thirteen Amp plugs before today.

An interesting post that I will certainly follow.

Dave.

[AdeV]

Don't start me on old computers...... I have a room full of Sharp MZ80K, A and Bs, with disks & printers, a handful of Sinclair QLs, an old Amiga kicking around somewhere, an Osborne OCC-1, a MicroVAX-3100, plus a load more...

I plan to hook some of the Sharps up to Arduinos & use them for data capture - just for a laugh really, and because they look cool compared to the <s>beige</s> black box/laptop.

[S. Heslop]

Don't start me on old computers...... I have a room full of Sharp MZ80K, A and Bs, with disks & printers, a handful of Sinclair QLs, an old Amiga kicking around somewhere, an Osborne OCC-1, a MicroVAX-3100, plus a load more...

I plan to hook some of the Sharps up to Arduinos & use them for data capture - just for a laugh really, and because they look cool compared to the <s>beige</s> black box/laptop.

That's an impressive collection. Especially the Osborne!

[Brass_Machine]

ahh... the memories. I had an Atari 1040st. Those were the days... Loading a game via tape (on an atari 800xl)! beeeeeeeep. Braaaaaaaap.

[S. Heslop]

In my lifetime i've only ever loaded one game off of a tape. It took so long I didn't want to do it again!

[vtsteam]

I have an Amiga 2000, I think a 500, once built an LNW-80 from bare boards (a hopped up color high speed (4mhz!) TRS-80 that I overclocked to 5.33 Mhz.), and I even have an original stock IBM PC stored away.

The last 16 bit computer I used was an old AT 486 DX66 clone, that served up until 5 years ago as a router under Coyote Linux, loaded off a floppy.

I'm thinking of resurrecting it yet again to run TurboCNC under DOS. The thing is a tank -- all metal case.

Anyway, following your progress Simon with great interest. As I mentioned FORTH works great with these old machines if you get into programming -- makes them lightning fast with tiny memory usage, and 16 x 64 screens are perfect for it. Easy to embed assembly language in it to do miraculous stuff, considering the age of these things.

[DavidA]

One of the big advantages with the old 8 bit machines,  particularly the BBc series,  was the number of pors available.

My Dell Inspiron lap top, three year old, only has three USB ports, one LAN port and it's dvd drive. Oh yes,  and the smart card dock. A bit limiting for experimental work.

The 486 below it has numerous serial ports + the LAN and a collection of jack sockets. As well as the 3.5" floppy and the DVD/CD drive.

And, of course,  that super useful printer port.

Dave.

[dawesy]

I have my C64 but the tape player doesn't work. Tried cleaning the heads and adjusting the azimuth but no joy have some classic games for it too.

[vtsteam]

I think any old casette player will work, you just have to add a connector to suit.

Most old tape players suffer from hardening/deterioration of the rubber pinch wheel. Sometimes a cleaning or even a light sanding with very fine paper will give the rubber enough grip. Speed variation can sometimes prevent the proper data playback. Often players used a rubber ring drive belt that goes bad and can be replaced.

I wouldn't be surprised if someone hasn't worked out a way to do a fake playback sound from a modern computer's headphone jack to load programs into an old 8 bit machine that had no other means of transfer. Though a homemade serial null modem might be another way of loading files if the comp was capable of using a modem.

Maybe you could also make a cart. I used to program eproms through a homemade parallel port eprom programmer, and erased them with a sunlamp.

[DavidA]

 These two links may come in useful for anyone who finds their Dallas Clock battery is dead.  It could keep a few old machines running,  and it is madmodding at it's finest.

http://www.mcamafia.de/mcapage0/dsrework.htm

http://classic-computers.org.nz/blog/2009-10-10-renovating-a-dallas-battery-chip.htm

Dave.

[awemawson]

Now these 'old' computers you are talking about are really quite modern !

When I first started using computers in the late 1960's they were pretty enormous, big cabinets with separate bays for the CPU and memory etc. We has serial CPU's and parallel ones, the former being the economy version as it cut down of the number of circuits required. Main memory was 'Core Store' - tiny ferrite rings threaded onto an X, a Y a 'Sense wire' and an 'Inhibit wire'. Backing storage was Drum memory and later rigid 'head per track' disc memory.

I well remember one night having to replace the 'disk enclosure' at a Mobil oil refinery - 2 megabytes of memory, but the system only took in high level language and compiled it at load time (Fortran in this case). I worked out that that night we had loaded 14.1 MILES of paper tape to reconstruct the 2 Mbyte disk image 

[S. Heslop]

I saw a thing a while ago where someone was programming for one of those gigantic 60s computers on punch tape. The punching machine was extremely noisy, sounded like a vacuum cleaner, and there was no facility to erase mistakes of course. Really makes me appreciate this modern era! When I was programming in Microsoft's visual studio it even had something like a spell check that told me if i'd made any typos, and an auto-complete to help me remember variable names. Although I've heard some more serious programmers complain that that kind of stuff stops you from actually 'thinking' about the code and how it works.

[AdeV]

When I was programming in Microsoft's visual studio it even had something like a spell check that told me if i'd made any typos, and an auto-complete to help me remember variable names. Although I've heard some more serious programmers complain that that kind of stuff stops you from actually 'thinking' about the code and how it works.

I still program in VS (2010 now, but I still prefer 2008); and yes, the autocomplete can be quite invasive (a bit like the so-called auto-complete on my phone, which makes more mistakes than I do). It doesn't, to my mind, stop you thinking about the code & how it works - if anything, freeing one from the drudge of having to remember exact variable names (and how they're cased if you're working in C#), frees one up to think more about the code, its structure & what its doing...

What it DOES hide from you, completely and utterly, is how inefficient the end result is. I was a lucky lad, having a Sinclair QL to play with - a cavernous 128K of ram, and a "blisteringly fast" MC68008 CPU (which was severely hobbled by it's 8-bit data bus - if only Sir Clive had stumped a few extra pounds up and used the MC68000 and got that 16 bit data bus that the Atari ST & Amiga made such good use of). Even so, one had to write tight efficient code to have it run at any kind of sensible speed. Not these days, most CPUs are idling most of the time, there's so much power in your average computer that utter garbage code still runs like a greased rat up a drainpipe.

[AdeV]

Don't start me on old computers...... I have a room full of Sharp MZ80K, A and Bs, with disks & printers, a handful of Sinclair QLs, an old Amiga kicking around somewhere, an Osborne OCC-1, a MicroVAX-3100, plus a load more...

I plan to hook some of the Sharps up to Arduinos & use them for data capture - just for a laugh really, and because they look cool compared to the <s>beige</s> black box/laptop.

That's an impressive collection. Especially the Osborne!

I dug the Osborne out last night... it "almost" works (the screen is exhibiting some kind of horizontal hold/echo/blurring problem), and neither of the disks in the case would boot, although I have a feeling that's because neither of them are boot disks. I think the problem is a dry solder joint, or possibly some dead caps, so I need to get inside it & have a furkle... Time will tell.

I missed a couple of machines out... I have a CBM 8032 with disk drives & printer (the 8032 being one of the last PET style computers). I used to have the holy grail - a fully working CBM PET 2001 with chiclet keyboard & "built in" tape deck (Actually a bog standard CBM cassette unit, held in a bracket & sticking out of a hole in the PET casing), but it is no longer with me unfortunately. Also I have, of course, a BBC B, a Tatung Einstein, a couple of Commodore SX-64's (the "portable" CBM64, with built-in screen & disk drive), a ZX81, no Spectrum oddly enough. Oh, I think there's a Commodore C128 lurking in a box somewhere...

Of course, I never USE any of the damn things, I probably ought to move most of them on... the QLs and Sharps I'll keep for sure, and the Ozzy... and the CBM, er, bugger.

[dawesy]

I think any old casette player will work, you just have to add a connector to suit.

Most old tape players suffer from hardening/deterioration of the rubber pinch wheel. Sometimes a cleaning or even a light sanding with very fine paper will give the rubber enough grip. Speed variation can sometimes prevent the proper data playback. Often players used a rubber ring drive belt that goes bad and can be replaced.

I wouldn't be surprised if someone hasn't worked out a way to do a fake playback sound from a modern computer's headphone jack to load programs into an old 8 bit machine that had no other means of transfer. Though a homemade serial null modem might be another way of loading files if the comp was capable of using a modem.

Maybe you could also make a cart. I used to program eproms through a homemade parallel port eprom programmer, and erased them with a sunlamp.

Cheers for that I'll have a look into it. Be good to get it up and running again

[John Swift]

I remember building a Sinclair ZX81 from a kit  - it worked first time !

there is still a number of ZX fans building their own ZX 80 and ZX 81 from scratch
http://searle.hostei.com/grant/zx80/zx80.html#ROM

last night I wished my PC had the same linear power supply
I switched on and bang  , the lights went out 

a capacitor in the mains filter had failed - the power supply works OK without it 

       John

PS
any one want to build a NASA guidance computer ?
http://www.galaxiki.org/web/main/_blog/all/build-your-own-nasa-apollo-landing-computer-no-kidding.shtml

[S. Heslop]

Don't start me on old computers...... I have a room full of Sharp MZ80K, A and Bs, with disks & printers, a handful of Sinclair QLs, an old Amiga kicking around somewhere, an Osborne OCC-1, a MicroVAX-3100, plus a load more...

I plan to hook some of the Sharps up to Arduinos & use them for data capture - just for a laugh really, and because they look cool compared to the <s>beige</s> black box/laptop.

That's an impressive collection. Especially the Osborne!

I dug the Osborne out last night... it "almost" works (the screen is exhibiting some kind of horizontal hold/echo/blurring problem), and neither of the disks in the case would boot, although I have a feeling that's because neither of them are boot disks. I think the problem is a dry solder joint, or possibly some dead caps, so I need to get inside it & have a furkle... Time will tell.

I missed a couple of machines out... I have a CBM 8032 with disk drives & printer (the 8032 being one of the last PET style computers). I used to have the holy grail - a fully working CBM PET 2001 with chiclet keyboard & "built in" tape deck (Actually a bog standard CBM cassette unit, held in a bracket & sticking out of a hole in the PET casing), but it is no longer with me unfortunately. Also I have, of course, a BBC B, a Tatung Einstein, a couple of Commodore SX-64's (the "portable" CBM64, with built-in screen & disk drive), a ZX81, no Spectrum oddly enough. Oh, I think there's a Commodore C128 lurking in a box somewhere...

Of course, I never USE any of the damn things, I probably ought to move most of them on... the QLs and Sharps I'll keep for sure, and the Ozzy... and the CBM, er, bugger.

How did you come into possession of such a collection? Two SX-64s is insane!

[S. Heslop]

I've been taking taking a look at the MaxYMiser music tracker for the Atari. I know a little bit about trackers but the instrument editor in this one is taking a bit of getting used to. But at least it has a relatively nice GUI compared to the nightmares that await me with the C64.



I took apart the C64C to measure the bits I want to keep.


Kinda interesting that the thing is held together with tabs. Even the keyboard is held in with tabs. Only the motherboard is held down with screws.


The whole thing is shielded.


No surface mount in sight.


And here's the famous SID chip. The lower number gives you the date, the chip was made in 1992, which is fairly late (they stopped making them in 93). Later is better with SID chips since the earlier revisions were fairly buggy, and some didn't have things like fully working filters or waveform combining.


Drawn up the keyboard and the motherboard.

I'm planning to make this thing reasonably compact, but i'm still not sure what i'm exactly going for. I could make something like this but imagining it with half an inch of dust settled on top and between the keys, it might be better to make something that folds or has a lid.

[AdeV]

Of course, I never USE any of the damn things, I probably ought to move most of them on... the QLs and Sharps I'll keep for sure, and the Ozzy... and the CBM, er, bugger.

How did you come into possession of such a collection? Two SX-64s is insane!

Ah, well, too much time & money on eBay mostly.... It's the usual thing, my old QL had died & I was feeling a bit nostalgic one night, some beer had been consumed, and I ended up purchasing another one. One thing led to another & before you know it I'm buying "any computer I ever used in the 1980s", then "any computer from the 1970s/1980s"... I must have had 30-40 machines at one point. That got whittled down quite a bit when the ex persuaded me to sell a bunch of them off (I think she wanted access to the garage), and has slowly grown again since she became an ex...

The ZX81 was kindly donated to me by the late AndyF of this parish; like everything of Andy's it was a study in neatness, being attached to a small baseboard with all of the leads & power pack attached "just so" with it; even the wobbly RAM pack is firmly affixed to the board to prevent the dreaded wobble... Sadly, the tape deck has died, but the ZX81 soldiers on...

Edit to add: The height of the madness was owning 2 HP1000 mini computers, each with separate tape & IO units, and each with 2 disk drives, and an HP A700. Each HP1000 had its own 6ft tall rack unit, the tape decks were a 2nd 6ft rack unit, the disk drives were about the size of a washing machine each, and the A700 came in its own 6ft cab which, I'm sure, was milled out of cast iron, it was massively heavy. I eventually sold them off as I couldn't do a damn thing with them, one went to a mainframe museum, the other spent some time in someone's kitchen before being moved on again to unknown pastures. I can't remember who got the A700. Crazy days...

[awemawson]

I really hanker after an Ampex TM7 or TM9 reel to reel tape backing store. I used to work on them in my callow youth.

They had three servo systems, one for each reel, and one for the capstan. Between the capstan and each reel was a vacuum column with a U shaped loop of tape that acted as a buffer to give the reel servos a bit of lee way, so for short back and forth reads or writes just the loops moved and the reels stayed still. Each loop had a photo sensor at each end, and when triggered the appropriate reel would kick in and wind a bit of tape. Lovely to see working when properly set up, and remarkably trouble free.

Biggest problem was carbon dust from the vacuum motors (that looked like a domestic cleaner motor) getting onto the electronics. There was a filter on it but they used to fall off! Followed by failure of the 'pea' bulbs in the photo sensors. If well used the heads would wear, increasing the head gap and reducing the output signal. (Complex heads - head per track (7 or 9), with a read after write head and an all track erase head)

[vtsteam]

 

[S. Heslop]

Here's one idea i'm looking at. It's a breadbin! Geddit?!

Looks kind of ridiculous, but i'm tempted to roll with it for the pun. It'd also keep the dust off the keys, but i'd prefer to go for a flat top for when this thing inevitably ends up in storage, or to rest stuff on top of in general.