These programmers also tried to preserve the original Boris timer interrupt value,
if pin 5 of F8 3850 chip (IO-03) would be HIGH instead of GND.
Code:
Interrupt Routine
5924: 5E LR (IS--),A
5925: 20 98 LI $98 ;<- faster timer interrupt value ( F8 table: 91)
5927: BF OUTS $0F
5928: 4B LR A,HL
5929: 5E LR (IS--),A
592A: 4A LR A,HU
592B: 5E LR (IS--),A
592C: 49 LR A,J
592D: 5C LR (IS),A
592E: 1E LR J,W
592F: 0A LR A,IS
5930: 13 SL 1
5931: 13 SL 1
5932: E9 XS J
5933: 59 LR J,A
5934: 62 LISU $02
5935: A0 INS $00 ;<- get in/out port 0 (port is inverted)
5936: 21 08 NI $08 ;<- AND 8 (bit 3)
5938: 94 04 BNZ $593D ;Branch if not ZERO
593A: 20 4F LI $4F ;<- original Boris rev1 timer value (F8 table: 183)
593C: BF OUTS $0F ;<- to 3853 chip
593D: A0 INS $00
593E: 1F INC
593F: 21 07 NI $07
5941: 5B LR HL,A
5942: 2C XDC
5943: 29 5D E6 JMP $5DE6
.
.
I tried it with a modified Delta-1 ROM in MAME, but it only blinks slower, still same weak game.