Powertran Cortex

[tms9995]

Hi Guys,

Well, I have to say this is the first time I've ever joined/replied to any online forum, but I felt the need to contribute. Every once in a while I type "Powertran Cortex" into Google to see what shows up and this time I found this thread!

I own two of these great machines, both fitted with the disk interface hardware. I have one here in the States, and one at my parent's house back in the UK. I also built a third one from a kit (the Cortex II - same internals but different case to look like a BBC Micro) for my best friend but that one is no more (but he's still my best friend!).

I know a lot about their workings etc. Your interest seems mostly in the disk interface and its use. It uses the TMS9909 Disk Controller and the TMS9911 DMA. The ROM (Cortex Basic) had a command called BOOT. This reads the first sector on the disk and executes it, which subsequently loads the remainder of the Disk Operating System from the disk.

There was a company called Marinchip Systems based out in California. They had various TMS9900 systems and a couple of Operating Systems. One was called MDEX (Marinchip Disk EXecutive) and NOS (Network Operating System). One of the key people there was John Walker and he initially created the foundation of AutoCAD on this platform! Micro Processor Engineering (MPE (or uPE)) migrated MDEX to the Cortex platform and that was its first 'DOS'.

The big problem was that MDEX was a completely different OS/environment to Cortex Basic. It was really a text-based/VT100 based OS, so none of the graphics were available. You couldn't run anything you had developed under Cortex Basic and the commands were very simple - kinda CPM ish. It pretty much made the Cortex HW emulate a single VT100 and that was it. It had a bunch of apps you could buy (I'm talking loads of money and I was 14!) such as QBASIC (compiler) and SPL (Systems Programming Language kinda like C) and some others.

A couple of years later, a guy called Neil Quarmby, who worked for TI in the UK (and I believe created the Cortex Basic release of TI Power Basic) released CDOS (Cortex Disk Operating System) and this was the cats ass! It was the disk extension to Cortex Basic. Turn the machine on, type BOOT and you were away! Everything as it was + a disk filing system - awesome! You chucked out the cassette player that night!

I have MDEX and CDOS on disks and they work. I have also written a Cortex emulator under Borland C++ Builder 5 (yeah I know that's old too) and have some disk images converted to PC files so that you can BOOT them. I also have just about every MDEX + APP manual. My biggest problem is that I'm extremely busy in my day to day stuff and I was somewhat reluctant to write this but since you have a shared passion, I couldn't resist. I would like to help revive this machine but need patience.

Hope this is useful,

Dave.

[nige the hippy]

Holy cow, I didn't know about Autocad! That makes it a historically important machine (well a bit!) instead of just the object of my droolings in ETI (Electronics Today International) magazine. Now that would be a nice bit of software to own.

And HELLO! and thanks for posting.

My day job is 2 toddlers and a half-finished house, so I'm a bit slow. I just can't help but say "yes" if something good comes my way. And my excuse for owning the number of machines I do, and not having enough time to work on them is that in a couple of years I will have enough time, but probably won't be able to afford the raw materials.

[tms9995]

Thanks for the welcome.

Reading back on my first post (ever!) I guess that sounded a bit rude about 'needing patience'. I didn't mean it to come off like that - I was just indicating it might take a little time for me to reply to any requests, so appologies if I got off to a bad start!

With regards to the memory-mapper. The correct part is 74LS612, but the 74LS610 can be used with pull-up resistors. It is not needed for normal use. The idea was using the '*' command (eg *PACMAN), Cortex Basic would page in 'external memory' (I guess it was conceived to be a ROM pack) and search for a header called PACMAN, load and run the chosen program. What most of us did was add 256K of RAM instead and write progs that we loaded into it upon booting CDOS. Although I never quite finished it, I created HDOS (Hard Disk OS) based on a SCSI interface that was loaded into the expanded memory. All good fun!

I got and idea this machine was released to ETI after TI abandoned the TI99/8. I know there are some differences but this machine is all TI so why they would design a complete computer for a hobby magazine is a little strange. Anyone have any info on this?

Not sure on the legalities of posting copies of CDOS, MDEX, ROMS etc. Obviously TI, John Walker and Mike Riddle (he wrote SPL for MDEX and was involved with the AutoCAD development) are still around. My emulator more or less works (no graphics modes yet but they never really interested me).

Anyway, here to help.

[nige the hippy]

I thought my machine a little strange in that it seemed complete except for the '612, but there were 4 jumpers on the pcb next to the '612 that seemed like options. It made sense if they were the 4 upper address lines hard-mapped straight through. I haven't had chance to meter them out, and I'm trying to resist doing projects 'till the loft space is usable. (Then.......)

Software wise...
If you actually know the people involved in the software, it would only be polite to ask, and I'm not sure how long copyright lasts, but I'd be inclined to at least send the binaries/images of the software you have to Al Kossow at Bitsavers for archiving, It's pretty secure as it's mirrored on quite a few servers. You may go under a bus next week( ), and maybe you have the only copies left.

Strange you weren't into the graphics, I was under the impression that it was one of the highlights of the machine.

Post didn't sound the slightest bit rude, there are some who post here fairly regularly who are on the autistic-spectrum and they usually get excused!

[tms9995]

I'm pretty sure the jumpers, as you say, just pass through the upper 4 bits of the address bus in the absence of the mapper chip. The CPU has a couple of its External Intructions (CKON and CKOF) decoded to turn the mapper on/off respectively. When the chip is fitted and in the un-mapped mode (normal), it simply passes through these bits. When on, it adds an additional 4 bits to provide a possible 256 4K pages (only 16 can be paged in at any one time) thus providing for up to 1MB of extended memory.

As for the graphics, well I guess you have to be somewhat 'artsy'! The TMS9928/29 VDP was pretty cool, but to do any fast hi-res stuff was quite difficult as the video ram was not accessible directly so you had to transfer it to CPU ram, manipulate it and then send it back via a couple of registers.

The 40x24 text mode was a little limiting, so a bunch of us upgraded to the backwards-compatible MSX Video Chip (the V993. This was available on a PCB from Maplin for some kit they had at the time. Someone came up with a package that patched Cortex Basic so that you had 80x26 text and some additional high res graphics modes (it had 128K of video ram instead of the original 16K).

I was attracted to this machine for a number of reasons. Firstly, when you powered it up it copies the ROM image into RAM. This makes it so easy to patch/enhance the operating system without having to burn some more Eproms! Secondly, because it was such low volume, there was a small community that, between us, pretty much had to come up with our own hardware and software which forced a learning curve that was really absent on any other platform at the time (and even now). It had a built-in assembler/disassembler and debug monitor where you could set breakpoints, inspect registers and so on. Not to mention it was 16 bits with hardware multiply & divide!

Basically, this machine allowed me to develop skills in assembly language programming and digital design that I have used in my professional life since. I work in flight simulation and, like the aircraft, these machines are around for a long time (a new one today would cost about $12,000,000). Hence it's not unusual to be doing a modification in 32 bit assembler on a super-mini that's circa 1978!

I don't actually know the people involved, I just know their names from looking at the MDEX software sources and documentation. From Googling, John Walker is the co-founder of Autodesk (!!!) and Mike Riddle is also still in the CAD business in Pheonix (bitter split between him and John in the mid-80's). You can hear him talking about the early days using the TMS9900 based system and his SPL language at
http://www.digibarn.com/stories/mike...ke-riddle1.mp3

There is no way of knowing that Neil Quarmby wrote CDOS. I just happen to remember sending him the cheque for it and getting his TI business card back with the order. He can be found with a quick Google too!

I suppose in light of the fact that I very well could have the only remaining copies of this stuff it would be prudent to back it up to a website/repository somewhere and just make it clear that is why it's there! As long as it's clear that for someone else to use it they should seek the permission of the respective copyright owners, it should be OK? It has no commercial value whatsoever and would be very educational for people to be able to experience what was available back then.

[tms9995]

How did that smily get in my post? It was supposed to be V9938. Like I said, I'm new...

[Ole Juul]

@tms9995: I was just looking around the net to see what one of those looked like. The Old-computers.com site has a little information but state that "We need more info about this computer ! If you designed, used, or have more info about this system, please send us pictures or anything you might find useful." It sounds like you have something to add.

[tms9995]

Thanks. I went over there and posted something in the 'comments' section. Hopefully that could stir something up? Hard to know what to send them - maybe the emulator...

[Ksarul]

Wow! Lots of nice additional bits of information there TMS9995! I just got a few of the TMS9909 and TMS9911 chips in from about the only place on Earth that seems to have stocks of them--Hong Kong/China. I got half a dozen of each of them just in case. . .but in all your posts I see two very important things (three, counting the fact that you have TWO Cortices): you have a lot of documentation that likely exists nowhere else, and you have a lot of the software to go with it. Please put those things up online somewhere.

I can also answer your TI-99/8 question. I am probably the only person in the world who has both a Cortex and a 99/8. I spent a several of years (and about 2K) tracking down all of the documentation for the 99/8 and then promptly photocopied it and put it up on the WHTech FTP site. I was told for years that most of the documentation I found no longer existed. I talked to the original engineers and dug up all but one item--the internal logic diagrams for the AMIGO chip. I have the complete operational description for it though, along with the pin-out, so I may just try and reconstruct it in VHDL one of these days. The Cortex and the 99/8 are VERY different. To see just how much so, you can look at all of the data I posted on WHTech:

ftp://whtech.com/datasheets%20&%20ma...-8%20Computer/

As a side note, work on the 99/8 began at about the same time ETI would have been preparing their first article for inclusion in the magazine. They were still testing two different versions of their motherboards in August/September 1983 to see which one was operationally better (two different expansion bus connectors/pinouts and some other component differences, most minor). The complete source code for the 99/8 system is on WHTech as well. I helped a friend (Dee Turner) rescue that from a dead hard disk about 20 years ago. It started my quest for 99/8 information.

Thank you for posting--I now know of a total of six Cortices that survive, though I have no contact with the owner of one of them. I also have some other questions: do you know which issues of ETI had Cortex articles in them after the Nov/Dec 1982 and Jan 1983 issues? I saw evidence that there were occasional additional articles in ETI up through at least 1987. I have the issues from Nov 1982 through Sep 1984 on their way to me via slow boat as of yesterday, so I will be able to make scans of some of that documentation from an original shortly. Do you have any means (and/or time) to bulk scan the documentation you have to easily put it up online?

Nige, I'm almost finished converting the Cortex BASIC manual JPGs I received from Germany to a fully-editable file (I'm starting the 22 pages of the appendices now, and then it will be done). I'll create a directory on WHTech for the Cortex and put it up there as both a PDF and a Word document, probably in about a week. Your wait is almost over, and much shorter than originally expected A work trip helped a lot, as I got to work in my hotel room uninterrupted during the evenings. . .

[tms9995]

Congrats on obtaining the FDC & DMA chips. They were both expensive and hard to come by in the 80's! The disk interface was designed to accommodate just about every drive and density combination available at the time and could be a little bothersome to get 'just right'. Although it catered for 8" drives, we all had some combination of 5.25 in 40T/80T Single/Double Sided/Density. When you finally achieved ownership of a pair of 80T/DS/DD drives (640K formatted capacity each) you felt like you'd won the lottery! Single Density was pretty reliable but the PLL for DD was a little sensitive to temperature etc. and could use a little tweaking from time to time. However, mine still works the last time I tried it!

We have a scanner with a sheet-feeder on it and I quickly tried a 36 page manual this morning and it scanned to a pdf in about 5 mins so looks like the A4/letter sized stuff should be easy.

I don't like reinventing the wheel, so is there a free site I can put this stuff on? I had a look at the whtech ftp site and there is loads of stuff on there but not sure how to add to it. If someone can point me to an account that's secure/safe/free, I'll upload some stuff.

As for the ETI articles, I think some of that stuff in still in the UK. I have a copy of something called Electronics Digest and it was basically an ETI Special that has the original 3 part series for the Cortex and some other select projects. I also have most of the User Group News Letters that contain loads of mods, tips, tricks etc. I'll scan the lot given enough time. The big one will be the firmware. I was lucky enough to be given the entire source code for the Eproms in a TI ring binder! It must be 4" thick of individual pages...