Sega Multigame

Hi all,

I decided to make a major push on the Sega Multigame this last weekend and
pretty much re-did the CPU daughtercard. I went for minimal size and parts
count instead of flexibility and "clever" factor. ;-)

The final board does the following:
-----------------------------------
Multigame-- Zektor, Tac Scan, Star Trek, Eliminator, and Space Fury.

There's room for three more games in the single 27C040 EPROM.

There's a menu-system triggered by NMI. (More on that below)

Menu system lives at 0xF000-0xF7FF. If anyone knows of a good reason NOT
to use this space, speak now! ;-) (If you know why I shouldn't use
0xF800-0xFFFF either I'd be curious to hear that too...)

My plan is to make a "kit" which includes the following:
--------------------------------------------------------

CPU daughtercard, fully assembled. You add Z-80 from your CPU board (it
plugs into the Z-80 slot).

New memory-decode PROM (replaces socketed one on the CPU board).

Security Chip "replacement". Just a "jumper board" that plugs into the
Security Chip socket.

The final cost of all of the above should be under $75 (depends on size of
PCB order). (There's a payment to Dave Fish in there as a pat-on-the-back
for cracking the security chip, and some $$$ to me for the menu-system and
project design/production.)

What about controllers:
-----------------------

The control-mapper is a separate board. For cash reasons I'll probably
need to wait until after the multi-game boards are done to run these. I
need to look at it again anyway to decide how to best hook it up. A Star
Trek control panel with a couple extra buttons is the preferred control
panel, but you can use anything you wish...

What about sound:
-----------------

Unifying the sound stuff is over my head for now. I'll leave that up to
anyone else. The CPU-daughtercard has five bits of "ID" that describes
what control mapping and Sound mapping should be used with a particular
game. Anyone that comes up with a good way of switching sound stuff (or
emulating it or whatever) can use the ID from the daughtercard to
automatically switch to the proper arrangement.

You can always physically swap sound boards too... The EPROM board isn't
necessary once the daughtercard is installed, so that frees up a slot.

---
So...  Anyone want one?  :-)  I'll do a run of PCB's as long as I get a few
people interested (like at least 10 including myself and a few others), the
more interest the lower the price might drop though.
I usually order a few extras, but I'll probably raise the price on them and
sell 'em to the "general population" in the newsgroup, so if you want one
cheaper speak now.
-Clay
Clayton N. Cowgill                                  Engineering Manager
_______________________________________________________________________
/\ Diamond Multimedia Systems, Inc.                      clay@supra.com
\/ Communications Division                        http://www.supra.com/