@iMacMiga:
Not to be an arse, but the HC+8 will actually even perform a bit worse than the onboard IDE-controller in an A4000.
The A4000 IDE-controller can reach above 3MB/Sec with a modern harddrive and a processor-card with good access to the motherboard bus and that is more than the HC+8 which manages a maximum of 2.2 - 2.4MB/Sec with a modern drive.
Then ofcourse the HC+8 is a dma controller which the IDE-controller in the A4000 aint and should thus lessen the cpuload. But as it is a Zorro2 dma controller, it wont in a Zorro3-machine be able to do dma transfers to/from the fastest memory, but only to slow chip-ram or Zorro2-fastram. This will force the cpu to work on the data in very very slow memory which removes all the advantage of a dma controller.
So my advice would be to skip the HC+8 and the SCSI-drives if they are causing trouble and just use an IDE-drive in your A4000 instead.
/Patrik