Reading Sinclair Interface 2 Roms
Philip Mulrane 25/6/2000
This document details my efforts to read Sinclair Interface 2 Roms,
in order to run them under some of the Spectrum emulators.
Contents:
History
Sinclair's interface 2 for the ZX Spectrum is a bit
of an odd wee puppy, comprising, as it does of a twin joystick interface,
using its own standard instead of the then dominant Kempston standard,
a pass-through of the expansion bus which is pruned, allowing only a ZX
Printer to be attached, and most importantly (for the purposes of this
document), a rom slot for cartridges.
There were ten such cartridges released by Sinclair:
They were intended to compete with the games
consoles of the day, but were not very successful.
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The slot
I used a multimeter to find out which connecting
pin of the slot corresponded to which bus signal. Here are the results:
The only point of interest here is that all 16
address lines are present, and the address decoding seems to be performed
by additional logic contained within the cartridges themselves. Maybe it
was planned to construct cartridges which would be able to map out the
upper 32K of ram in order to allow cartridges larger than 16K? My electronic
knowledge fails me at this point, maybe someone else out there could enlighten
us on this one.
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Reading the roms
In order to read the cartridge roms, I constructed
an adapter allowing me to plug the cartridges into my BBC micro eprom programmer:
I then copied the rom images to my PC via an Archimedes.
Hex dumping through the roms reveals that most of them are only half full!
And the ones that are full are padded out by a 'loading screen' 6912 bytes
long. I have images for nine of the roms:
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Use with emulators
To use a given rom with a given emulator, you need
to replace the 48K basic rom with the rom of your choice. Some emulators
have an option for this, for other's you need to rename the existing 48K
basic rom so that the emulator can't find it, and then copy the cartridge
rom to a file with the same name as the original 48K rom.
I've tried the rom images with several emulators:
-
Gerton's Z80 3.05, no problems.
-
X128 OS/2 0.5, no problems.
-
!Spectrum on the Archimedes, no problems.
-
X128 0.93 (DOS), strange crashes, maybe he patches
the rom in some way?
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Help!
As you can see from the above list, I'm missing one
of the original cartridges: Pssst. It would be great if someone out there
would be prepared to swap/loan the missing cartridge, so that I can read
it's contents, and make them available to the great Specyfying public.
I have about 7 of the carts as doubles, so I
might
be prepared to do a two for one swap.
If you are interested please email me at:
info@mulrane.com
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