Megatron1999 Posted January 25, 2015 Share Posted January 25, 2015 Hi. For anybody that's never heard of the Powertran Cortex, it was an advanced UK self build TMS9995 microcomputer..with some very impressive specification for 1983 ! See :http://www.powertrancortex.com/ I'm looking into reverse engineering and redesigning the old Powertran Cortex to make a modern up to date version. This obviously is quite a large project (to say the least!) and will take a considerable amount of time and effort. The New specification (DRAF) will hopefully be similar but better than the original TMS9995 Safely overclocked at 16/4MHz128K SRAM 100ns512K NVSRAM 100ns (2pcs ?)128K ROM 100nsMemory mapper IC (MMU)TMS9901 PIO ICTMS9902 SIO ICReal Time Clock RTCMath Co-ProcessorFDC Floppy Disk ICCF Card interface (8255)PATA IDE Interface (8255)V9958 Video PAL/NTSCSN76489 Sound Chip PSGSAA1099 or YM3812 PSGKeyboard Decoder IC (PS/2) ?Anybody interested please leave a message ** This will be a Big Project ... so i'll need all the help i can get !! 1 Quote Link to comment Share on other sites More sharing options...
HackMac Posted January 25, 2015 Share Posted January 25, 2015 (edited) If you start such a big project, you have to think about tools! Not only the parts you want to wire. When many people work together on the same things you have to choose the right tools such a source version control system, issue tracking, specification and documentation tools, hosting for the sources or an CAD program for the layout of PCBs, etc. I don't know any project in the TI scene witch is started in this way. It will be great if it happens, but I believe all hardware projects (and software projects too) are done by one person (perhaps one more, someone in the neighborhood). Everybody is puzzling for him/her self and sometimes when you can't go on, there comes out a request in a forum. Thats all. I think you should not wait for the others, just start for yourself. matthew180 wrote in an other thread: "More work, less talk." Edited January 25, 2015 by HackMac Quote Link to comment Share on other sites More sharing options...
+Ksarul Posted January 25, 2015 Share Posted January 25, 2015 Three of us worked on the UberGROM project--Tursi, Acadiel, and I spent quite a bit of time behind the scenes puzzling out the intricacies of getting that one to work properly. Gazoo then took the result and ran with it! That was refreshing. . . 1 Quote Link to comment Share on other sites More sharing options...
Megatron1999 Posted January 26, 2015 Author Share Posted January 26, 2015 (edited) Initial Notes : CPU As TMS99xx ICs are obsolete, all ICs will be Working Pulls from old kit TMS9995 CPU 16MHz Crystal DIP40 package : Price about $7.0 each Parallel Interface TMS9901 DIP40 A parallel interface will be supplied via CRU bus to a TMS9901 PIO Serial Interface TMS9902 A Serial interface will be providied via CRU bus to a TMS9902 SIO Memory Memory Management Unit 74LS672 128K SRAM 100ns (fast for a TMS9995 system) TC551001-10 or similar DIP32 1024K NVSRAM 2pcs DS1250 100ns DIP32 128K or 256K EEPROM W27C010 or similar Video circuit (V9958) The V9958 will be used for PAL/NTSC TV output as these are still available as NOS and are cheaper than both the TMS9929 and V9938. I also have full working schematics. The V9958 cost about $5.0 each Sound Two sound Chips will be used: SN76489 as used in the Ti-99/4A SAA1099 or YM3812 Storage PATA IDE interface provided by an 82C55 IC Compact Flash again by 82C55 IC Floppy disk Interface : TMS2797 IC A Cassette Interface will NOT be provided plenty of working schematics exist for these ICs. Real Time Clock (RTC) The DS12C887 will be used as this was used in IBM PCs. got working schematic, still can be sourced. It will provide Clock / Calendar Functions Math Co-Processor Probably use the Generic AM9511A 4MHz to give Trig, Log and other Math & scientific functions thus helping to speed up the processor. Keyboard (PS/2) Could use the original type designs ? But will probably use a small micro-controller to read a PS/2 keyboard. Reset / CPU Supervisor MAX705 The MAX 705 will act as a RESET / CPU supervisor IC Glue logic: In the original Powertran Glue logic was TTL ICs.. I will go for using a low cost CPLD as this will simplify the board design and give greater flexibility. Exapnsion connector: An expansion connecotr will be fitted with CPU signals etc to connect a daughter board for future epansion. Edited January 26, 2015 by Megatron1999 Quote Link to comment Share on other sites More sharing options...
Megatron1999 Posted January 26, 2015 Author Share Posted January 26, 2015 (edited) Costings and Timescales Costing of ICs Price Each in $ USD TMS9995 $7.0 KM681000-10 / HM628128 etc DIP32 128K SRAM 100ns $1.0512K NVSRAM 100ns DS1250 $2.0128K ROM 100ns W27C010 or W27C020 $1.0Memory mapper IC (MMU) $2.50TMS9901 PIO IC $2.50TMS9902 SIO IC $2.50Real Time Clock RTC $2.50Math Co-Processor $2.0FDC Floppy Disk IC $8.00CF Card interface (8255) $1.50PATA IDE Interface (8255) $1.50V9958 Video PAL/NTSC ( Video Circuit complete $10)SN76489 Sound Chip PSG $0.50SAA1099 or YM3812 PSG $1.50Keyboard Decoder IC (PS/2) ? $1.0 Approx $50 for all ICs by-passing ebay prices , though ebay is getting cheaper lately for these TMS chips. connectors / sockets /resisitors / diodes / caps etc $20 DIL Sockets $5.0 PCB ?? not know .. Guess $55 Total cost approximately (A guestimate !) <$150 ! Timescales ! An estimated 6-12 Months to design and build a prototype this will have a Simple Test ROM which will prove hardware functionality. Later a Modified Powertran Cortex OS will be used .. hopefully ?? Edited January 26, 2015 by Megatron1999 Quote Link to comment Share on other sites More sharing options...
+Ksarul Posted January 26, 2015 Share Posted January 26, 2015 TMS9901 and 9902 chips have been difficult to find at prices less than $5-$7 each in quantities below 100--even as used pulls, the moment you try to source them from anywhere but China. TMS9995s are generally in the $12-$25 range from US or European sources--with the low end for used pulls and the high end for NOS chips. Most of those suppliers won't talk to you for quantities below 100 or so chips of each type either (some will, but the minimum order size per line item will still range from $250-$500). I buy chips on the wholesale market when I have need for enough chips to get past their minimum order sizes. . .and if you decide to try to use the TMX9909 from the original Cortex, they are still out there, but the last quote I was able to get was for about $30 per chip with a minimum order of 25 chips. Quote Link to comment Share on other sites More sharing options...
Megatron1999 Posted January 26, 2015 Author Share Posted January 26, 2015 I know someone in the UK that has sourced these type of ICs and he's told me the prices . I then contacted the suppliers , he recommended myself and they quoted the same figures. The Chips are Pulls .. so there's some risk and I'd have to build small test boards to test them myself as trying to build a system with DUFF chips would be both infuriating and somewhat stupid. I have got these chips before from China and on the whole they're OK.. but as mentioned you need to test them as soon as they arrive. so all in all I think ( or know from experience) that my prices are in the 'Ball-Park' . I've seen people on ebay.com advertise TMS9995s at $130 each !! But the high price does not guarantee they'll work ! Quote Link to comment Share on other sites More sharing options...
Megatron1999 Posted January 26, 2015 Author Share Posted January 26, 2015 Using Powertran Cortex as Test Rig to Test ICs I was looking for a powertran Cortex PCB to build a working Powertran and use is as a Test-Rig to test ICs. This would (probably) be easier then designing my own homebrew test-rigs. And would let me detect any DUFF ICs that would cause a headache ! Quote Link to comment Share on other sites More sharing options...
bad robot Posted January 26, 2015 Share Posted January 26, 2015 Sounds like a great project... though too ambitious for my skill level... Good Luck ! Quote Link to comment Share on other sites More sharing options...
Megatron1999 Posted January 26, 2015 Author Share Posted January 26, 2015 Created a Google Sites Web Page/Site.... at the moment it is rather Naff ! But hopefully over time it will evolve into something better ! https://sites.google.com/site/homebrewpowertrancortexproject/home Quote Link to comment Share on other sites More sharing options...
bad robot Posted January 27, 2015 Share Posted January 27, 2015 Have you got many people interested ?? Quote Link to comment Share on other sites More sharing options...
mnbvcxz Posted January 27, 2015 Share Posted January 27, 2015 Since the Cortex is designed to be expandable to 1MB memory, you could use 2 x 512KB static ram chips, and have a "bootstrap loader" entering the OS/BASIC into ram at power up from CF card eliminating the need for a rom. Quote Link to comment Share on other sites More sharing options...
jens-eike Posted January 27, 2015 Share Posted January 27, 2015 That is just what the Cortex does: copying the content from the EPROMs to RAM, then running the OS from RAM. Great idea, you can modify any BASIC command :-) What is wrong with ROM, if you don't have to worry about slow access speed... Quote Link to comment Share on other sites More sharing options...
+mizapf Posted January 27, 2015 Share Posted January 27, 2015 @all potentially interested people: in case you don't already know, MESS contains an emulation for the Powertran Cortex. Not in the same quality as the TI emulation, but things can be fixed, I suppose. This could be interesting for people who don't yet know whether they should get involved. Quote Link to comment Share on other sites More sharing options...
jens-eike Posted January 27, 2015 Share Posted January 27, 2015 Another note: check your timing requirements. 100ns RAM could be too slow for worst-case operation. Consult the data book, from address stable to data in is much shorter than 330ns! According to my TMS9995 Data Manual (December 1984), page 56, the access time is 3/4*tc2-135 (3/4*333-135=114ns with a 12MHz clock, at 16MHz: 3/4*250-135=52ns). Subtract any delay from TTL buffers or decoders like 74LS244 (30ns) or 74LS138 (39ns) and a '245 (40ns) buffering the data bus (maximum values from The TTL Data Book 1987). As you can see, LS-TTL logic is not going to make it, that's why TI invented the automatic first wait-state. Using faster logic (ALS/F/ACT...) and really fast RAM (628512 is available in 55ns) can do the trick. 1 Quote Link to comment Share on other sites More sharing options...
Megatron1999 Posted January 27, 2015 Author Share Posted January 27, 2015 If 100ns memory is not fast enough then it can easily use 70ns NVSRAM / SRAM and 70ns EPROMs then that would be fast enough .. and 70ns are as easy, and cheap to obtain as 100ns ! 70ns 128kx8bit SRAM are $1.0 each and 512kx8bit 70ns NVSRAM are $2.0 each ... whereas 512K SRAMs are $3.50 each.. plus NVSRAM can clearly retain data there's no need for a boot loader as there'll be plenty of ROM & RAM .. This way it could have 640K RAM, 128K or 256K EPROM/EEPROM and space for memory Mapped I/O. Quote Link to comment Share on other sites More sharing options...
mnbvcxz Posted January 27, 2015 Share Posted January 27, 2015 What is wrong with ROM, if you don't have to worry about slow access speed... I was just saying you could eliminate the rom entirely, no need to have it on board, no need to program the rom and you can have any number of other OS's or languages which would not all fit in the rom, how about a CP/M like OS, nice and simple. Quote Link to comment Share on other sites More sharing options...
Megatron1999 Posted January 27, 2015 Author Share Posted January 27, 2015 The beauty of ROM is it's reliability .. they're bullet proof .. CF Cards, Floppy Disks can all be corrupted. To load an OS from disk could be an option but having ROM may still have advantages for reliability and instant loading ! Plus there'd be plenty of RAM ... 640K compared to the original 64K !!! Any OS could be loaded/stored in NVSRAM anyhow ! This way You have your Cake and Eat it .... SRAM , Non-Volatile RAM + ROM.. Plus let's face it....... it's a bit premature to worry about this ¬? Quote Link to comment Share on other sites More sharing options...
JamesD Posted January 28, 2015 Share Posted January 28, 2015 Did TI ever introduce an optimized version of the TMS9900 with a 16 bit bus or did they stop with the TMS9995? I wonder if several of the support chips could be duplicated in a CPLD. That could simplify the board. Quote Link to comment Share on other sites More sharing options...
+Ksarul Posted January 28, 2015 Share Posted January 28, 2015 The TMS99105 and TMS99110 chips carried the family on a bit further, as did the TMS99000 that I have. The military grade chips were optimized for somewhat higher clock speeds (up to 24MHz, IIRC), but were otherwise unchanged. 1 Quote Link to comment Share on other sites More sharing options...
bad robot Posted January 28, 2015 Share Posted January 28, 2015 Could the TMS9902 & TMS9901 work with the TMS991xx CPU at 24MHz ?? Quote Link to comment Share on other sites More sharing options...
jens-eike Posted January 28, 2015 Share Posted January 28, 2015 The TMS991xx can add wait states to any operation (memory, internal, cru), so it should be possible to use the 9902. The 9901 can be replaced by '251 (input), '259 (output) and '348 (interrupt priority) TTL chips without speed penalty. Bonus: the TMS991xx can do parallel I/O for CRU addresses above >8000 Quote Link to comment Share on other sites More sharing options...
Stuart Posted January 28, 2015 Share Posted January 28, 2015 Could the TMS9902 & TMS9901 work with the TMS991xx CPU at 24MHz ?? The timing crystal is 24 MHz, but again this is divided by 4 internally to give an effective clock speed of 6 MHz. Quote Link to comment Share on other sites More sharing options...
bad robot Posted January 28, 2015 Share Posted January 28, 2015 The problem with the TMS991xx CPUs , other than they’re hard to source, is that being DIP40 all the Data/Address lines are multiplexed on top of the other complexities & idiosyncrasies of the chip would make it a headache to interface ?? Quote Link to comment Share on other sites More sharing options...
simon ti99 Posted January 28, 2015 Share Posted January 28, 2015 Has anyone on the forum built / designed a TMS99105/TMS99110 system ? Quote Link to comment Share on other sites More sharing options...
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