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Xenophon

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Posts posted by Xenophon

  1. Posted

    I suppose the easiest design would be



    A Z80 CPU (Z84C00xx) CMOS Z80


    74LS138 or 74HC138 Memory decoder


    6264 (8K SRAM) x 3


    AY3812 Sound Chip (I/O decoded using a GAL)



    al this would plug into the Z80 socket, though the original Z80 CPU would need to be replaced first. The beauty of this design is that it fits inside the CV's Case and doesn't need to be connected via the expansion socket. Though some soldering work would need to be done.










    Any ideas or suggestions are welcome !

  3. Posted

    Hi.

     

    I was toying with the idea of design/building an Accelerator board to fit inside the CV . something quite simple but powerful enough to be useful. It would plug directly into the existing Z80 footprint.

     

    Plugs into Z80 socket on CV board.

    has Z84C0008PEC 8MHz (switchable between 3.58 and 716MHz)

    24K SRAM 3 pieces 6264 SRAMs

    8K EPROM ( uses original CV ROM)

    Memory decoding done using 74HC138

    GAL used to switch between Standard 3.58MHz and Turbo 7.16MHz mode when hFF I/O is written to ?

     

     

    The PCB would be quite small and inexpensive...

     

     

     

    Any ideas or suggestions are welcome !

  4. Posted

     

    Thanks Nanochess,

     

    This is exactly what I wanted to know. It looks like if I were to make some hardware I would need to keep the mirroring just in case some software used a mirrored address. So does the software do a write to port 7Fh just to make sure if it's plugged in an Adam that it puts it into CV memory mode? Sorry if these seem like simple questions. I have never programmed for these platforms and want to be sure exactly how the hardware operates. Also do you know if I were to have the 24K ram enabled all the time in a colecovision if it would still run all the software correctly? I realize that some of the new software will think it is an Adam. What I am trying to accomplish is putting some of the address decoding into programmable logic. I want to make sure it is software compatible.

    What type of hardware are you thinking of building ?

  9. Posted

    The Obvious PROJECT is build a completely NEW TI-99/4A .. the way it should of been built .. with more RAM , better graphics etc , yet still 100% backwards compatible.

     

    TMS9900 CPU (as in original)

    TIM9904A

    TMS9901s

    TMS9902s to give serial I/O

    MORE RAM

    MORE ROM

    possibly even using a 74LS612 Memory Mapper?

    Cartridge Slot as in original

    V9958 video with 192K VRAM

    SN76489 PSG

    YMZ284 (AY-3-8910) Sound Chip

    Real Time Clock

    Maths FPU (AM9511 or similar) to speed up maths functions

    8255 PIO for internal PATA IDE (CF card or Hard-Drive)

    etc etc

     

    Have a Turbo Mode where the TMS9900 is clocked at 16MHz(4MHz internall) , done by software.

    • Like 3

  10. Posted

    Perhaps just start with a simple homebrew design as a starting point, something like:

     

    Z80 CPU

    Cartridge Slot (32K Cart as original)

    8K SRAM

    8K SRAM

    8K SRAM

    8K EPROM

    74HC138 + 74HC139 Memory decoders,

    (24K SRAM + 8K OS ROM)

     

    V9958 Video board with sound

    Possibly Four expansion slots for add-ons and prototyping new hardware.

     

    The controller circuitry and stuff for 'Joypads' etc could be copied from the original CV ?

     

    I've already seen several working V9958 schematics and at least one V9958 VDP board so quite a bit of the work has already been done.

     

    This type of thing could be done as a hobby with little to no funding.

  13. Posted · Edited by Xenophon

    My draft design (to breadboard) would be :

     

    Z80 CPU

    (possibly Z84C0006PEC or Z84C0008PEC) as these are very cheap:

    http://www.ebay.com/itm/10PCS-Z84C0006PEC-Z80-CPU-Encapsulation-DIP-/371218968377?pt=LH_DefaultDomain_0&hash=item566e5fef39

    http://www.ebay.com/itm/10pcs-Z84C0008PEC-Z84C0008-DIP-40-/171399504172?hash=item27e834e12c

     

    SRAM (static RAM) as opposed to the original DRAMs .. probably use 64K to allow CP/M option ??

     

    EPROM 27C64 for O/S etc ?

     

    V99x8 Video (seen several schematics of boards already done) making this somewhat easier

    SN76489 Sound Chip

    YMZ284 / AY-3-8910 Sound chip for MSX sound

     

    Glue logic / could be TTL /PLD/GAL or a CPLD yet to decide

     

    Shall start breadboarding as soon as stuff arrives, all going well !

  14. Posted

    I've been pondering for some time about building my own Super Colecovision console/computer and now I feel iit's the time to strike ! So I've bought some breadboard, wire, already had tools soldering iron etc and am now doing a draft design and looking at what components ICs I'll need. OK my knowledge of microcomputers and electronics isn't great, but that's the whole point I'll be on a steep learning curve and even if I don't make a working Colecovision (which is most likely) at least I tried and learnt stuff on the way !

     

    Is anyone else doing a similar sort of thing >?

     

     

  17. Posted

    The Sega Master System uses a Large DIP 64 IC as it's VDP some modes are compatible with the TMS9918A, but it uses a TILE mode and multicolor SPRITES. It's also very hard to get exact technical data for the Sega Master video Chip. Anyone that's looked inside a Sega Master system will of spotted the unusual DIP64 IC that's the VDP.

     

    It could be implemented on an FPGA, but then you could argue why not just do the whole thing on an FPGA !

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