In this topic about the exciting new RGB mod for the 2600, collinp reported that the XRGB-mini had problems syncing with Warlords.
I took a quick look and noticed that VSYNC was set before the WSYNC, instead of after, which resulted in the sync signal starting late in the scanline.
I did a quick hack via Stella to swap the order. The hack resulted in the kings getting shifted to the right, but was enough for collinp to confirm that moving the VSYNC after the WSYNC did indeed fix the problem.
Today I fixed the sync and king positions by modifying the source I documented back in 2006. The source can be used to compile the original ROM or an XRGB-mini compatible build by use of the constant XRGBMINI:
; set to 1 for VSYNC fix for XRGBMINI, set to 0 for original XRGBMINI = 1 ... StartOfFrame: LDA #$82 ; P-----V- P-paddles are dumped to ground, V-vertical Blank is started if XRGBMINI = 1 ldx #$50 ; move left 5 STA VBLANK STA WSYNC ; Wait until end of 1st V-Sync scan Line STA VSYNC ; Start Vertical Sync STX HMM0 STX HMM1 else STA VBLANK STA VSYNC ; Start Vertical Sync STA WSYNC ; Wait until end of 1st V-Sync scan Line LDA #$20 ; Move Left 2 STA HMM0 ; 3 5 STA HMM1 ; 3 8 endif