A Homebrew Z80 system with V9958 Video..

Par Dirty Harry

Resident (45)

Portrait de Dirty Harry

13-01-2015, 20:06

Hi.

Just spotted this website demostrating a Working Z80 (MSX like) system. May be worth a look if you're making a homebrew MSX machine ?

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

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Par megatron

Resident (41)

Portrait de megatron

18-12-2015, 16:13

I was thinking of building my own Homebrew Z80 (MSX type) machine, just for the hell of it on breadboard.

Spec:
Z80 CPU (obviously)
512K SRAM
256K EPROM
CPLD as Memory mapper switching in 16K Pages
V9958 Video
AY-3-8910 sound Chip
GAL22V10 as I/O decoder
A micro-controller would do quite a bit of the house keeping / Keyboard/ joysticks etc

I'd Copy (plagiarise) as much stuff/schematics from Old Datasheet and MSX data-books/Manuals. Keeping everything as simple as possible producing a sort of MSX 2 console/games machine or that's the idea !!

Par hit9918

Prophet (2921)

Portrait de hit9918

18-12-2015, 23:10

you mention mappers but no slots.
an MSX can work without mappers, but not without slots.
the intel 8255 for port A8 slotflip.
8bit in two-bit pairs select 4 16k pages from 4 slots.
together with the AY who too got ports, you got all the "keyboard joystick etc" done.
look at MSX1 boards with discrete chips.

it is all a little chip list except the slots.
unused things shall not mirror with other pages or other slots. because software searches all slots.

the minimum MSX2 would be like
slot 0 0x0000 - 0x7fff bios + BASIC ROMs
slot 1 slot connector
slot 2 0x0000 - 0x3fff subrom
slot 3 64k RAM

and 128k vram. it is not in the slots, only the VDP touches it.

Par RetroTechie

Paragon (1563)

Portrait de RetroTechie

19-12-2015, 02:43

Building it may be half the fun, using it is the other half. But if you build a one-off system, you'll have virtually no software to run on it.

If you make it (somewhat) compatible to an existing system, you can run that system's software on it. Or easily port software. Not just for fun, but also for testing purposes.

There's several systems based on Z80 + TMS9918, so with Z80 + V9958 you'd have some choice there. MSX is not the simplest system due to its slot mechanism, otoh it's very expandable and there's lots of nice software for it. I wouldn't be surprised if it's possible to make Z80 + ROM + RAM + V9958 (+VRAM) boot an MSX1 bios ROM (no slot mechanism, 8255 or PSG). From there on it's just a matter of adding chips / tweaking the config.

Par Louthrax

Prophet (2413)

Portrait de Louthrax

19-12-2015, 03:04

Would a simple 64KB/linear/non-slotted RAM chip with
* BIOS at 00000h - 03FFFh
* Konami ROM at 04000h-0BFFFh
* RAM at 0C000h-0FFFFh
work or even boot ? (without BASIC).

Par sd_snatcher

Prophet (3503)

Portrait de sd_snatcher

19-12-2015, 03:26

For MSX1? Yes, it works.

Par syn

Prophet (2096)

Portrait de syn

19-12-2015, 14:42

After all this talk about diy msx, I am curious: are there schematics or instructions available somewhere on how to build a complete MSX from scratch?

I mean, I am a total hardware beginner. If I buy the hardware components like megatron, dirty harry and some others have mentioned in the many topics regarding this, where do I go from there? How do I proceed?

Par st1mpy

Paladin (849)

Portrait de st1mpy

19-12-2015, 14:49

... this type of thread just goes around in circles, there was a similar one around a year ago with the same people here.
You will not manage to make the whole computer on a bread board with jumper wires, so just buy this GR8Bit