Soldiers of Fortune (USA) main menu glitch

[shadowlmd]

Main menu is glitched until a d-pad key is pressed. This doesn't happen with BlastEm core, so maybe it's a bug.

I compiled genesis_plus_gx_libretro.so myself from the source code in this repository. All settings are defaults.

Steps to reproduce:

1. Load Soldiers of Fortune (USA).gen (md5: b90ff517cba6492377e02d23fcda4b80)
2. When music starts, press Start to go to main menu

Video: https://youtu.be/_CCaV85M29g

[ekeeke]

This seems to be caused by my (quite approximate) emulation of 68k cpu delay when z80 cpu accesses 68k bus, removing this line fixes this issue.
What happens is that some VRAM writes sequence to initalize sprite becomes interrupted by vblank interrupt and does not finish properly, leaving the displayed screen half finished. When above delays are not emulated, the VRAM writes sequence starts earlier and does not get interrupted.

I will need to find another way to emulate this which is more accurate or at least less prone to introduce timings errors.