i also seem to remember is that the A4000 is based on the A3000 design which in turn is based on supporting 030 chips and bus bursts etc. to from zorro space.
the reason you get good bench results with an 030, is that the bus interface was designed for an 030.
the commodore 040 card didn't support bursting modes, or various other things, so the worst CPU card to bench with is the A3640. the main changes in the rev11 buster over the rev9 were to support the crappy bus signal from the A3640 card.
phase 5 built their cards based on this design and had some interface logic between the 040/060/PPC chip and 030 bus to properly support the various burst modes etc.
from what i remember, this was the major update between the cyberstorm1 and cyberstorm2 series logic, and continued into the cyberstorm3/PPC range.
not sure about any other accelerator manufacturers, but this can easily be found in the speed the CPU can access chip ram.
with my EC030, cybII040, and cybIII060/PPC it was around 7Mb/s, but with my Warpengine040 (28Mhz overclocked to 40Mhz! yehaa! big fat heatsink & fan, attached with heat xfer compound and superglue - FPU thought it didn't exist tho it still worked(?)
i was looking at about 2.5Mb/s
(buster rev9 and rev11)
so from my expirience, the best cards to bench with are either 030's or phase5 designed cards on A4000's
