29 Dec
2012
29 Dec
'12
10:18 a.m.
On 12/28/2012 10:55 PM, John Wilson wrote:
Sure, if it's that simple. I wrote a driver for
the ISA and the PCI
version too (the first one -- doesn't the later PCI board need to have FPGA
code fed to it at runtime?) and *never* got them working reliably, because
junk bytes appeared in the buffer often enough to make reading impossible.
That may be true for the CW MK4, but that was not the case for MK3 PCI.
I suspect that if you try to implement this with a PCI-ISA bridge chip,
you'll be in for agony supporting legacy DMA correctly. I've got a
couple of P3 mobos with Intel 810 and 815 chipsets that use the National
bridge chip to support ISA slots. Legacy 8-bit DMA absolutely fails on
both of them from the ISA slots. Oddly, the built-in floppy support
(Super I/O chip) works just fine, but ISA DMA doesn't work at all.
I haven't the faintest idea why--the chip datasheet says that it
shouldn't be a problem. Earlier Intel chips (e.g., 440) don't have this
issue, as ISA support is part of the deal.
--Chuck