Since this was bumped, I might as well post it now. Looks like mame now has a way for the diehard driver to set the us bios. Hasn't been done yet (0.129), but I'll bet before 0.130 comes out it will have it, which will mean no diehard.ini with just the one bios line in the near future.
Is there any way to speed up this game? it plays a little bit off the pace for my liking
What mame number, CPU, and OS (32 vs 64 bit) are you using? Looks like
0.128u4 had a major slow down for stv.c games (diehard). (I'm going by vfkids, another stv game.) 64 bit OS and mame helps a lot over 32 bit, but if your OS isn't 64 bit, no help there without installing new OS. Also, check the benchmarks and if your computer is less than the ones that run vfkids at 100%, very little to do.
