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dirty-harry

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Posts posted by dirty-harry

  1. Posted

    Combining them all into one chip might give you some serious available pin issues and force you to one of the larger CPLDs, negating much of the advantage you gain price-wise. The 74LS612 and the TMS9901 are 40 pin packages--and they use them. There are only a few that can be cross-utilized. The same goes for the TMS9902, although that is a much smaller package.

     

    Most of the chips show up pretty regularly in any event. When I need larger quantities, there are a lot of wholesale parts vendors with access to some serious quantities out there--though pricing can be a bit bad unless you order a lot of them. . .

     

    The idea to make modern equivalents isn't a bad one though--but I haven't seen files for any of the chips you've identified here out in the wild. You'd probably have to start from the beginning and develop your own--though you might be able to use the MAME emulator to validate exactly what each of them is supposed to be doing.

    There's quite a few low cost CPLDs out-there nowadays so that's no big problems and they are all faster than the old 74 TTL/CMOS chips . The 74LS612 has a 40ns propagation delay.. so a faster version of that (10ns) would be good. though I'm not sure how much I could squeeze into say a EPM7160SLC84 ?? Plus having ALL peripheral ICs on one chip would seriously cut down on board complexity and cost !

  2. Posted

    Hi.

     

    As some TMS99xx chips are getting harder to source, I was thinking of popping some of them (their functionality at least) onto GALs/CPLDs. I was thinking of putting :

     

    TIM9904 (aka 74LS362) Clock Generator

    74LS612/610 MMU

    TMS9901

    TMS9902

     

    Possibly TMS9901+TMS9902 + MMU all onto one chip ?

     

     

    Has anyone done this before or got HDL code / boolean equation for their functionality ??

     

    Thanks

     

  6. Posted

     

    You need to understand the mindset of government contractors and the MOD work .. it can often take 15 years... yes 15 yrs for a government/MOD project to be completed. The specification for Eurofighter was laid down in 1986 .. the project wasn't fully completed until after 2000 ! The Eurofighter is reputed to use a Motorola 68020 CPU .. high-tech in 1986 ! Also government & Ministry work is very bureaucratic leading to huge delays..

    So when a missile project is started in say 1977, the TMS9900 would be State of the Art , however it may not be completed until 1990!! And have a life expectancy of 15 yrs.. So they could be still using that missile in 2005 !

  7. Posted

    When buying ICs from China it's best to check them as soon as they arrivem then you can correct any problems straight away. I've found most suppliers tend to be good at sorting things out. Plus ebay will give you your money back if things go wrong.. ! I've got Duff stuff from Chinese suppliers but they either sent replacements

    or give a full refund.

  9. Posted

    Initial design would be based on costing and component availability

     

    Draft Specification would be :

     

    TMS9900 CPU PDIP64

    TIM9904A PDIP

    TMS9901 PDIP Parallel I/O

    TMS9902 PDIP SIO Serail I/O

    62256 SRAMs ( x 2) 16K bytes SRAM

    M27C128 UV EPROM (x 2) 32K bytes ROM

    Paged/banked ROM or NVRAM yet to be decided (512k Bytes?)

    TTL glue logic OR a CPLD to reduce cost

    V9958 Video VDP with 192K DRAM

    SN76489 Sound Chip

    AY-3-8910 or YM2149 Sound Chip with parallel ports

    8255 PIO for IDE / CF Card

    PS/2 Keyboard interface

    Atari Joystick interface x 2

    Real Time Clock RTC

    Maths Co-processor ?? Yet to be decidied

    Expansion connector for Daughter board to be fitted

     

    TIM9904 clock with 16MHz Crystal (overclocked) giving 4MHz Bus !

     

    Spec for Daughter Board (optional):

     

    FDC Floppy Disk Controller

    Speech Chip

    Second IDE interface for IDE Hard-Drive

    Ethernet

     

     

    Note it's not intended to be a direct replacement for the original Ti-99/4A as the original computer had some weird idiosyncrasies. Only partial backward compatability would be achievable. Memory mapped I/O etc (were possible) would match tto he Ti-99/4A.

     

    IC costing :

    ( Main / Motherboard )

    TMS9900 CPU PDIP64 $2 each

    TIM9904A PDIP $2.0 each

    TMS9901 PDIP Parallel I/O $2.0 each

    TMS9902 PDIP SIO Serail I/O $2.0 each

    62256 SRAMs ( x 2) 16K bytes SRAM <$1.0 each

    M27C128 UV EPROM (x 2) 32K bytes ROM <$1.0 each

    Paged/banked ROM or NVRAM yet to be decided (512k Bytes?)

    TTL glue logic OR a CPLD to reduce cost CPLD (EPM7128) $2.0 each

    V9958 Video VDP with 192K DRAM $8.0 (for V9958+DRAMs)

    SN76489 Sound Chip <$0.75 each

    AY-3-8910 or YM2149 Sound Chip with parallel ports <$2.50 each

    8255 PIO for IDE / CF Card <$2.0 each

    PS/2 Keyboard interface (small cheap MCU <$1.0 each)

    Real Time Clock RTC $2.5 each

    Maths Co-processor ?? Yet to be decidied $2.50 each

     

    I'd could get all the ICs for about $32

     

    With a PCB , connectors, resistors etc I'd try to make it for $60.

     

    Some parts of the circuit have already been designed.. there's a working V9958 board on the web as a template for the video circuit as well as lots of other bits and pieces which could be modified as desired (with owner's permission).

     

    Costing Daughter Board (optional):

     

    FDC Floppy Disk Controller $2.50 each

    Speech Chip $3.50 each

    Second IDE interface for IDE Hard-Drive $2.50 each

    Ethernet $2.50 each

    PCB $25

     

    Total cost approx $38

     

     

     

    Timescale would be about six month to get a working prototype up and running.

  10. Posted

    The idea is more to make a 'Kit' something like the original Powertran Cortex.. The Design would be open-source .. you'd buy say the PCB and source the ICs , resistors etc yourself or even buy a kit of parts ? Then You'd build and test it yourself. In the Same way the GR8BIT is to MSX (but simpler and much cheaper). It's not about building a computer.. you can get a second hand PC from ebay for peanuts ! It's about building and learning about microcomputers . Most Modern stuff is either surface mount or Microcontrollers ! And lots of modern stuff is way to FAST to breadboard as the wires act like radio-transmitters..making it more of an RF project !

  11. Posted

    Has anyone done or thought of doing a Kickstart project to raise Money (seriously) to make a NEW TI-99/4A .. possibly out of sourced working TMS99xx ICs. Just updating the original design to take advanced of more modern SRAMs and V9938/58 VDP etc, yet still being software compatible. Ideally making it for less than $100 ! The design would be made Open-Source.

  12. Posted

    A uncommon British machine from the early eighties (1983): The best way to describe it : It was a cross between an MSX and Colecovision, using a Z80 CPU, SN76489 Sound Chip and TMS9918/29 VDP, 32K or 64K RAM , 24K ROM, running at 4MHz.

     

     

    http://en.wikipedia.org/wiki/Memotech_MTX

     

     

    A team of Brainiacs (two mainly: Dave and Martin) have brought it back to life as a fully working , enhanced prototype: It's even been clocked as high as 40MHz, using a Z84C0020VEC (PLCC44) Z80 CPU. It's hoped in the not to distant future that a series of professional Single board Computers (SBCs) will be made from these prototypes ?? These may even be morphed into full MSX machines (perhaps that's just wishful thinking )??

     

     

    http://www.primrosebank.net/computers/mtx/projects/mtxplus/mtxplus.htm

    http://www.primrosebank.net/computers/mtx/projects/mtxplus/mtxplus_arch.htm

     

    Games are still being written and ported to the MTX, so there's still life in the old machine yet !! A 'New' enhanced version would have a Big speed increase and much improved graphics and sound..

     

    Spec for new machine ( DRAFT)

    Memotech MTX S3

    Z80 CPU running at up to 16MHz ( been clocked at 40MHz in lab)

    640K RAM (128K SRAM, 512K NVSRAM, 70ns)

    64K or 128K EEPROM 45ns

    Z80 CTC

    Z80 DART (SIO)

    Floppy Disc Controller ??

    8255 PIO to read CF cards

    EPM7128 as glue logic

    V9958 VDP with 192K VRAM

    SN76489 PSG

    YM2149/AY-3-8910 PSG (to give MSX Compatability)

    RTC Real Time Clock

    PS/2 keyboard

    etc etc ..

     

    Will (hopefully) have some MSX compatability

     

    Lets wait and see what materializes !

     

     

  13. Posted

    Hi.

     

    If anyone is into designing and building homebrew electronics / computers than this site may be of interest:

     

    http://stores.ebay.com/paelectrocomponents?_trksid=p2047675.l2563

     

    I know it's a bit of a plug but I was so tired of seeing ICs for stupid prices on ebay that I talked this seller into selling kits at near wholesale/trade prices. Buying ICs separate for a project can get ridiculously expensive, so they'll also make bespoke kits up to order , prices are negoatiable..

     

    ** note

     

    Always ask for NOS (New Old Stock ) rather than pulls...

    Check that they've tested the ICs are working

    Use Anti-static handling

    Ship with Anti-static foam.

     

     

    Hope this is of use !

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