'new rom' refers to Basic 2. When Basic 2 was released there was no version number displayed, so it was just referred to as 'new rom', with Basic 1 referred to as 'old rom'. Only when Basic 4 came out did people start calling them Basic 1 and Basic 2.

Fortunately for you there is little difference between Space Invaders for Basic 2 and 4. I wrote a little diff program to see what the changes were. Only ROM interrupt entry location needs to change.

So load your Basic 2 version, and using the Machine Language Monitor change:

0511 a9 2e becomes a9 55
0516 a9 e6 becomes a9 e4
0a51 4c 31 e6 becomes 4c 58 e4
19a5 4c 31 e6 becomes 4c 58 e4

Dave

Can you read the disk status from the command channel to see if the device is present? The equivalent of the Basic program


10 dv = 8 : rem device to test
20 open 1,dv,15
30 get#1,A$
40 if st = 0 then print "present"
50 close1


So in machine language


lda #$00
sta $96 ;status
lda #$08 ;device #
sta $d4 ;device
jsr TALK ; $f0d2 in basic 4
lda #$6f ;secondary address
sta $d3
jsr SECND ; $f143 in basic 4
jsr INPUT ; $f1C0 in basic 4
jsr UNTLK ; $f1ae in basic 4

lda $96 ;get status
beq present

Hi


The LED will only light when running Commodore's diagnostic software. It is turned on by a normally unused keyboard scan-line value. Official Commodore dealers had a small box that was clipped onto the CPU which contained the diagnostic software in ROM.


Schematic (LED is near bottom right corner, driven from E9 NAND gate): http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/2001/320130-1.gif


Dave

Scott Adams has a web site with links to downloadable and web playable versions of his adventure games.


http://www.msadams.com/downloads.htm

I've uploaded DDGames1 disk image to the "PET Games" section. It should appear there when approved by Admin.

I've uploaded DDGames2 disk image to the "PET Games" section. It should appear there when approved by Admin.