Hello,

Thanks to a NetBSD supporter who wishes to remain anonymous i got ahold
of SWCTX-BX Vaxstation Turbochannel adapter and certain other
Vaxengoodies.

My initial tinkering shows that Turbochannel adapter ROM (SWCTX-BX's
ROM) is mapped to 0x36000000 and the option board (whatever one plugs
into Turbochannel slot) is mapped to 0x30000000. Option board is mapped
1:1, meaning that offsets of various bits and pieces of option board are
located in same manner as they are on Decstations. Memory accesses to
this region (0x30000000 and onwards) access the option board directly,
with lowest byte of each longword accessing the hardware, 2nd byte of
each longword being address counter within given "subsystem" (in DEC's
nomenclature "subsystem" is one integral component of each option board,
say firmware ROM or NCR53C94 or RAMDAC, etc.) address range. Top two
bytes contain 0xffff and are irrelevant. 

I've been thinking about TC bus implementation for NetBSD/Vax. My idea
was to add a dummy Turbochannel bus (similar to vsbus) which would probe
for DWCTX-BX and print out the name of attached device from option ROM
(if any were found). Then the hardware specific driver (stolen from
NetBSD/Pmax/Alpha port) would grab the device and do whatever it
normally does, simply accessing the card through the address window. My
guess is that whatever DWCTX-BX ROM does it is limited only to POST and
MIPS emulation and that thing bears no influence on operation of TC
option once OS takes over (conversion to VS system bus is transparent).

Thoughts, suggestions, clues are welcome :-)

Thanks to the anonymous donor, Isildur and eBay i now have PMAZ, PMAD,
PMAG-B and DEFTA-UA to test the TC slot with.

BTW, if anybody happens to have a DWCTX-BX adapter technical docs i'd
really appreciate them. I will dump its ROM and check it out either way
but it'd be far easier to start with technical description so i know
what that thing does and what it doesn't do.

Blaz Antonic
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