Al Unser Jr. Turbo Racing

This page details bugs of Al Unser Jr. Turbo Racing.

Timer Bug#

In time delayed scenes, a timer is used stored at location 6460 in the game's SRAM. Due to a branch instruction oversight, it mistakenly cuts off 256 frames too soon, thus cutting off the full music track for said scenes.

8997    dec $6460  ;decrement timer (lower byte)
899A    bne $8972   ;if it's !=0, branch to beginning of subroutine
899C    lda $6461   ;if not, load higher byte
899F    beq $89A6   ;if that equals 0, branch to 89A6
89A1    dec $6461   ;decrement timer (higher byte)
89A4    bne $8972   ;then branch to beginning of subroutine, which will fail if the higher byte is decremented from 1 to 0, which will skip 256 frames. Replacing the instruction with a BPL will fix this.
89A6    lda #$00    ;load 0
89A8    sta $6462   ;store in $6462
;end
89AB    rts     ;and return

Original	Fixed
Turbo_Racing_original.mp4	Turbo_Racing_fixed.mp4

The following Game Genie codes will fix the bug and revert the timer to its intended behavior.

Japan: AOXAOLEI
US/Europe: AOXAKPEI

Music Bug#

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In the second unused theme of the PAL version, the square channels go out of sync with the triangle and noise channels with every loop. This does not occur in the NTSC version, and may have been a botched PAL conversion. It is most likely it went unnoticed during development since the songs are not used.