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Hello from Saffron Walden

R

retrohimpi

Member
Joined
Jun 11, 2010
Messages
36
Location
Saffron Walden, UK
Hi everyone,

I'm a recently retired software engineer, living in the ancient market town of Saffron Walden, Essex in the UK and currently emulating my first single-board computer (Ohio Scientific Challenger 1P) in Java. I've managed to more or less recreate the 1Mhz, 8Kb RAM, cassette-based system I owned from 1979-82, and am now trying to upgrade it to the 48Kb, dual-floppy version. It's at the stage where it can apparently boot from an OS65 v3 disk image but, although it clears its screen, no banner message or prompt appears and, if I break in via my front panel controls, it appears to be stuck in the serial printer driver, a port which I'm not currently emulating. I'm still trying to track down where it's going astray (I've already had to emulate a 60Hz video refresh strobe, which the DOS needs to calibrate its timing loops whilst booting). I do my software development in NetBeans on a white MacBook or a big, fast Linux box, also using cc65 and P65 (a Perl-based 6502 assembler).

I don't deliberately collect vintage hardware, though I still have my TI58 programmable calculator and print cradle from 1978, an Pentium 5 PC purchased in 1996 and assorted modems and inkjet printers. As well as Java, I can program in various flavours of BASIC, 6502 assembly language, Perl, C and awk. In 1982, I traded in my trusty C1P for a 48Kb Apple II Europlus, for which there's now several orders of magnitude more available software and docs, and sometimes play with the MESS emulation of that system. Before I moved on to an IBM PC clone, I added a Z80 card to my ][+and taught myself to use CP/M, so I'm hoping to eventually add at least an 8080 to my own emulator.

My principal interests at the moment are tracking down documentation, disk images, etc for Ohio Scientific hardware/software, and 6502 test programs (my emulated CPU still has the occasional bug and doesn't fully reproduce the undocumented behaviour of the original). However, I have fond memories of my home computing adventures in the seventies and eighties and enjoy hearing about others' experience on other hardware of the day. Hopefully my years of programming experience will also enable me to respond to software questions on the forum.

Back to debugging my struggling emulator...
 
Welcome,

I have one of those OSI Challenger 1Ps in my collection. It's the most vintage in my collection I think!

Tez
 
tezza said:
Welcome,

I have one of those OSI Challenger 1Ps in my collection. It's the most vintage in my collection I think!

Tez
Click to expand...

Amazing - I didn't think there were many of them left. Sadly, I had to trade mine in to pay the deposit on the Apple ][+ that replaced it and have no idea what happened to it after that. Does yours still work? Do you have any software for it?

I've only recently discovered that, completely unbeknownst to me, there is a computer history museum (http://www.computinghistory.org.uk/index.htm) just a few miles north of here. They have a C1P too, and I'm hoping to arrange a visit soon to see the real thing again after all these years. They also have books like 'The First/Second Book of Ohio Scientific' in their library, which I've never found on-line.

I've just started a blog here, and hope to post some screenshots of my emulator there soon.
 
Oh, right. I remember finding this site back when I first started Googling for Challenger info, but I didn't realise until just now that it was yours. I remember deciding to grit my teeth and get the 4Kb RAM expansion along with the rest of the hardware, convincing myself that I'd never be able to justify/afford it afterwards. It took me years to pay off my credit card (the whole lot cost me more than 3 months take-home pay in those days, and I still had to swap out the mains transformer for a 240V one myself before I could use it), but the extra RAM made all the difference. I wrote my own text adventure, a video game that had the Enterprise zooming back and forth at the top of the screen, demolishing tower blocks below with its phasers, and started developing a very [over]ambitious multipass BASIC compiler.

I bet it felt great when you finally got yours to work. I had to write and debug thousands of lines of code before my emulator would do anything useful at all but I can still remember that yell of triumph when I first saw the familiar D/C/W/M? monitor prompt appear. It would take another week to suss out and emulate the keyboard matrix before I could respond to the prompt and get BASIC to fire up, but that was the first point at which it began to look as if I hadn't bitten off more than I could chew. I'm hoping for a similar adrenalin rush when I get my disk emulation to boot properly.
 
Tardy as usual but welcome to the forums :) I had waited to reply until I had some time to read about your city. Maybe the greener grass syndrome but it seems so much neater history over there. Maybe it's just the history one connects to personally that makes it seem interesting in some areas and not others. Regardless very neat endeavor you're on. In the off chance that some folks skip over the intro pages you might want to post some information on your emulation project in a separate post. I'm fairly confident a few members here have Challenger's but how many of them know the technology or have used them is another story.. plus my memory could just be making it up ;-) I won't name names but I think you'll get a few more folks who may have some info if you need it.

Do you have a site hosting any of your progress? Not sure if you've seen Mark Csele's site but he seems to have some schematics as well as feature comparisons which may help understand what might work on certain systems but not others.

- John
 
Hello there, from not so far away if I may be of use, however I'm very much more of a hardware person, I do a lot of assembler & quite a bit of basic. but I'm afraid that I never got round to mastering "real programmers" languages (I started learning C at night school, but felt like the chap teaching knew little more than me) & my atitude is that I don't tend to do something unless I have a use for it, so I've never carried on.
I'm actually a fairly depressive sort of programmer. Usually by the time something works absolutely correctly, all elation has gone & I'm just glad to see the back of it!
Your post just reminded me, I must have another chat with Jason from your local museum, He very kindly sorted me an old cd-rom drive with a panasonic interface out & a family crisis got in the way of me actually getting hold of it.
 
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barythrin said:
Tardy as usual but welcome to the forums :) I had waited to reply until I had some time to read about your city. Maybe the greener grass syndrome but it seems so much neater history over there. Maybe it's just the history one connects to personally that makes it seem interesting in some areas and not others. Regardless very neat endeavor you're on. In the off chance that some folks skip over the intro pages you might want to post some information on your emulation project in a separate post. I'm fairly confident a few members here have Challenger's but how many of them know the technology or have used them is another story.. plus my memory could just be making it up ;-) I won't name names but I think you'll get a few more folks who may have some info if you need it.

Do you have a site hosting any of your progress? Not sure if you've seen Mark Csele's site but he seems to have some schematics as well as feature comparisons which may help understand what might work on certain systems but not others.

- John
Click to expand...

Thanks for the info and advice.

Yes, it's very historical around here - lots of thatched cottages and timberframed buildings, but the narrow streets are often choked with cars. Yesterday, on a 15 mile trip to Cambridge we were stuck behind a cement lorry for 5 minutes whilst it unloaded and later behind an ambulance picking up someone who needed to be hospitalised in a hurry for another 10 minutes. In both cases it was the cars parked opposite and on either side of the obstruction that made it impossible to get past.

I've started a blog here about my adventures in booting my C1P emulation from a disk image. I'm not sure how to reference it, but you can access it from my personal settings page or, at the moment, from the Blogs section of this site's home page (look for the retrohimpi labyrinth avatar). I've made some more discoveries since then, and now have a somewhat better idea of what's going on, but am still no nearer a solution - there'll be a blog update coming soon, and I'll post about it in the Other Systems section where, hopefully, other Challenger enthusiasts will see it.

Yes, I do know about Mark Csele's site, which has been very helpful, thanks, and also http://oldcomputers.net/osi-600.html, which helped me to sort out exactly which boards were in which models. I have downloaded scans of most of the user manuals, schematics and service manuals for the various boards, but they don't go into enough detail of exactly what has to be emulated (eg, it's pretty hard to work out the address of a chip from the decoding logic on the schematic and next to impossible to determine the clock rate of a serial I/O chip). I've either been lucky and found a description somewhere, or else had to reverse engineer the source code to work out what's where and how it works. Not that I'm complaining, though - it goes with the territory and, the longer it takes to understand and work round the problems, the greater the high will be when I eventually get there.
 
nige the hippy said:
Hello there, from not so far away if I may be of use, however I'm very much more of a hardware person, I do a lot of assembler & quite a bit of basic. but I'm afraid that I never got round to mastering "real programmers" languages (I started learning C at night school, but felt like the chap teaching knew little more than me) & my atitude is that I don't tend to do something unless I have a use for it, so I've never carried on.
I'm actually a fairly depressive sort of programmer. Usually by the time something works absolutely correctly, all elation has gone & I'm just glad to see the back of it!
Click to expand...

I agree entirely and have only ever taught myself languages that I'm going to use, whether for work or play. Over the years I've found that by setting myself a succession of small, attainable goals I can keep myself motivated and rewarded, and afterwards I deliberately forget all the pain and hassle along the way and just enjoy the quiet satisfaction of "I wrote that!".
 
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