I've been chatting to the original author of the NetBSD/dreamcast patches for the DCEXT and he has been generous enough to search for and share his memo on the hardware changes he made to the DCEXT to get it working:
- it's better to have external 5V power source
(rather than using Vcc from DC)
- Vcc and ground lines might be weak and needs more capacitors
- DC connector P9 should be NC and P12 should be GND
- IDE P1 (reset) needs some power on reset signal
- CPLD P50 (interrupt) should be connected to DC P13, not P8
- ISA IRQ lines should have pulldown
- It's better to ISA IRQ 5,9,10,11 rather than 3,4,6 etc
- ISA A14 and A15 in the patern might be swapped? (not sure)
(12.08.2012 23:28)OzOnE писал(а): The netBSD code is interesting too. If most of the routines are in place for PIO, I might try to add the G1 DMA routines to it.
@abs - I could send you some code too? The routines for DMA are probably much simpler than for the G2 bus.
I'm happy to look at any code, though I never managed to get or make a DCEXT board... :/