dirty-harry

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 !

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

Has anyone ever made an 'Accelerator board' for a TI-99 ?? Something that probably plugs into the CPU socket. A small PCB with a TMS9900 CPU + 32K SRAM + EPROM switchable between 12/16MHz with an RTC ?? & 100% backward compatible.

Are there other people interested in Z80 DIY hardware design..perhaps we could get enough interest to make a user group or Forum ? Getting people into designing & making hardware must be a good thing !

Spotted this on ebay.com http://www.ebay.com/itm/Zilog-Z80-Colecovision-Kit-8MHz-Z80-MSX-Homebrew-/151686369904?pt=LH_DefaultDomain_0&hash=item2351365270 Bought stuff from them before and they are OK to deal with, though stuff from China takes forever to arrive !

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 !

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.

Hi. Is there a Colecovision II Console in development or is it just a Myth ?? And when is it due out !

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.

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 !

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.

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 !

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 !