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Powertran Cortex

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    Powertran Cortex

    Anyone else on the forum have a Cortex? I just got one and I don't have a lot of information on it yet.

    For those wondering why it is in the TI section, it uses a TMS9995 microprocessor and all of the ancillary support chips are TI as well, even the disk controller (which I am still trying to acquire, as the disk subsystem components were not installed on the machine I got).
    Enter My Mind At Your Own Risk!

    I do, mine's missing the memory map chip, but I'm still trying to find out if that was an option, and also hoping to need some other silicon to put together a worthwhile order for spares. It has however got the disk drive bits in place.
    I lusted after one of these after seeing the articles published in ETI (Electronics Today (International!)) all the schematics (and construction details - it was a kit) are available as PDFs online (I can email you them if you send me a PM). from rusty memory I'm not sure that it wasn't a "Transam" design, so it may share some design heritage with the equally obscure "Wren Executive" also Alasdair McRae-Birch (who still exists) may have had someting to do with it. but I don't know for sure.
    "Don't it always seem to go
    That you don't know what you’ve got ‘til it’s gone" (BANG )


      I have all of the documentation that was on Oldcomputers--along with a couple of additional pages that came with mine that weren't in the Oldcomputers archive. As of this morning, I also have the 220 page manual for CORTEX BASIC. A friend of mine in Germany sent it to me when I asked about the machines yesterday on one of the Yahoo groups. He also has one, though his needs a new power supply. Like mine, it does not have the disk subsystem installed. Reading the manuals, I didn't see a way to actually FORMAT or SAVE to the disks listed. Everything was based on booting a program from the disk (which should be in IBM3270 Format?) .

      I understand your long-term lusting after one of these--I've been trying to get my hands on one since around 1988, though the hunt only became continuous in the last ten years or so. . .do you need the BASIC manual?
      Enter My Mind At Your Own Risk!


        I have a frontal cortex, does that count?


          Originally posted by Ksarul View Post
          I understand your long-term lusting after one of these--I've been trying to get my hands on one since around 1988, though the hunt only became continuous in the last ten years or so. . .do you need the BASIC manual?
          I'd love the basic manual. pdf, I presume (!) if it isn't, it's probably as cheap to get it scanned, as it is to get it photocopied (and a lot cheaper to post) it's probably worth sending a copy to "old" .| "bitsavers" for archiving too. I was going to peek the rom for keywords had it not existed.

          Funny about the disk system possibly not being fully supported, looking at the original article it's "glossed over" a bit I wonder if the code was never properly written - or if they ran out of rom! In 1982 disks were still a minority interest.

          The chap in Germany should be able to rebuild the power supply fairly easily. Even if the transformer's gone away he could replace it with a standard 12-0-12 toroidal one, and wind on the winding for the 5V. It'll probably only be about 20 turns of thickish (about 1mm^2) wire
          I suppose if the supply is missing completely, a little pc one would do the job with the power control wire shorted to ground to turn it on.

          It was way in advance of anything available to the mere mortal at the time!
          "Don't it always seem to go
          That you don't know what you’ve got ‘til it’s gone" (BANG )


            The manual version I have is in the form of 220 pages of GIF images. I've been converting them to an editable text document, but the going is slow because the copy I have is relatively bad, so the OCR software needs a lot of help to turn it into something useful. I've finished the first 10% or so of the manual in the last week or so. It is still a lot faster than typing it in manually. I will send you a soft copy as soon as I'm finished with the conversion. If you need it sooner, I can send you the raw GIF images.

            I'll let my friend in on your idea with the power supply. Many thanks!
            Enter My Mind At Your Own Risk!


              sounds like a labour of love!
              Have you considered running a spell checker through it first? (Or is that the way you're doing it anyway) Usually quicker than manually reading & correcting.
              I wonder how many Cortices there are still out there? you've probably got half a week's work per existent machine.
              We owe you!
              "Don't it always seem to go
              That you don't know what you’ve got ‘til it’s gone" (BANG )


                Well, I know of three confirmed machines: mine, in the USA, my friend's in Germany, and yours. I also know of one more that was sold on eBay a few months ago. That is more than enough for me to ensure manual preservation. . .and a spell checker doesn't help rebuild mangled tables, unfortunately. I actually just did the pages as raw text dumps and then rebuilt the formatting on my own as a project to keep me busy during random moments of downtime. That way, I finish 2-5 pages at a whack and don't spend enough time on it at any one time to get bored with the task.

                I've also been looking at the memory map chip issue--it should only need the memory mapper if you are trying to build the 256K memory option. The 74LS610 is getting really difficult to find anymore (there is a seller on eBay wanting $30 each for them), but there is also a guy on one of the 6502 forums who designed a plug-in board with relatively common LSI chips to substitute for one (probably would cost more than the $30 chip, but it would be fun). It should be relatively easy to write a VHDL program that works like one as well--then it could be done with a single-chip replacement. I'm just starting to learn VHDL though, so it may be quite a while before I can look at something like that. It would give me VHDL practice since I eventually plan to reverse-engineer the gate arrays for a 99/8 though.

                I am still scouring my parts sources for better prices on them though, since that is the primary option. Most of them only had the 74LS612 though, which is similar but with fewer registers.
                Enter My Mind At Your Own Risk!


                  The schematics show the '612 - ebay (uk) item shown below

                  Item number: 180273705894

                  but I'll check

                  Reason I'm doubting it's need, is 4 jumpers (4 address lines?????) near the chip, which I couldn't find on the diagrams, and that mine's missing. I could do with knowing the truth before powering on. I suppose I could lift the board & start "knife & forking" * it through, but I have other priorities at the moment.

                  * meter & patience (rather like removing fish-bones)
                  "Don't it always seem to go
                  That you don't know what you’ve got ‘til it’s gone" (BANG )


                    I went back to the schematics again--the block diagram lists a 74LS610, but the parts list and the rest of the schematics list a 74LS612. I ordered a bunch of the 612s from a supply house I regularly deal with (Unicorn) just in case. I'll look at the board on mine to see if either chip is installed later today.

                    Not sure why they would have been using four jumpers for address lines there, unless they were using 16K memory blocks in a 256K range. That does plot out at least, if two of those jumpers also feed back into the original memory chip array address lines. The other possibility would be that each line activates a single, 64K block--again, the other end of the line will give clues to see if that is the case. If I fish-bone mine to see where they go, I'll post the results here. . .
                    Enter My Mind At Your Own Risk!


                      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,



                        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.
                        "Don't it always seem to go
                        That you don't know what you’ve got ‘til it’s gone" (BANG )


                          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.


                            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!
                            Last edited by nige the hippy; June 13, 2009, 09:04 AM.
                            "Don't it always seem to go
                            That you don't know what you’ve got ‘til it’s gone" (BANG )


                              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

                              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.