Slow mode for the Cybervision64 (NOT the CV64/3D) is Jumper 1 (JP1)
set to CLOSED. This only works (from the manual) on cards with serial
numbers of 81xxxxx. The manual states "the CV64 to operate in an old
Buster compatible mode...even with Buster chip 11...because on the
A4000 motherboard are some components that may also influence Zorro-3
bus timng beyond acceptable tolerance."
I hope that helps.
