Here's some more info on Harry Dodgson's monitor cart....
Vectors:
FF00 NMI
FBD0 Reset
FF03 IRQ
; Reset
FBD0: sei
FBD1: cld
FBD2: bit $28
FBD4: bpl $FBD2
FBD6: clc
FBD7: lda $DFF8
FBDA: adc $DFF9
FBDD: bne $FBE2
FBDF: jmp ($DFFC)
; NMI
FF00: jmp ($0140)
; IRQ
FF03: jmp ($0142)
To write your own 7800 cart:
1) use the upper 4K from the monitor cart
2) use the following data
$DFF8 = 0
$DFF9 = 0
$DFFC = startLo
$DFFD = startHi
3) and at some point set $140 & $142
That's it....
You'll notice that 16K would be the minimum size you can make.
$8000-$DFF7
$DFF8-$DFFD data
$DFFE-$EFFF
$F000-$FFFF 4K image
Now the question is regarding legality of using that image.
It's pretty obvious he left this "backdoor" in on purpose.
FWIW, here are Harry Dodgson's most recent email addresses
from a Dejanews search:
hdodgson@xxxxxxxx
hdodgson@xxxxxxxxxxx
These are fairly old though.
----
Since we're talking about the 7800....
A quick rundown of General Computing's work:
1) Super Missile Attack (arcade)
upgrade/mod for Missile Command
2) Quantum (arcade)
part of settlement with Atari over SMA
3) Food Fight (arcade)
part of settlement with Atari over SMA
4) MsPacMan (arcade)
modified Namco Pacman
sold to Midway
5) 7800 & some 7800 games
6) Laser printers
Hmmm, I used to have their website address.
They were still in Massachusetts.
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