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From: fargo@iear.arts.rpi.edu (Irwin M. Fargo)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Two of everything (summary of replies)
Message-ID: <7'7^9J=@rpi.edu>
Date: 23 Jan 91 09:39:19 GMT
Organization: Fargo HQ, Inc.
Lines: 70
Nntp-Posting-Host: iear.arts.rpi.edu

I'd like to thank all those who replied to my original post.  The information
cleared up a number of things.

Before I start the summary, I'd like to ask where I can find some good
references on maps of the PC (preferrably 286 and 386 AT machines) I/O
address space, interrupt table, and memory address space.  I have a few
books here and there that give tidbits of info about this stuff, but they
don't go into a lot of depth and even present some contradictory info.

I remember that when comp.sys.ibm.pc was around, someone used to post a
list of all interrupts for the PC.  If someone could point me in that di-
rection, I'd really appreciate it.

Onto the summary!

Having multiple serial/parallel I/O cards depends on the cards you buy.  Some
cards have jumper settings for many different IRQ's and base I/O addresses
while some don't.  Basically, you have to be careful about what cards to in-
vest in.  Ironically, most cards that can be set up for anything other than
COM1 and COM2 with any ease are the cheap $50 cards you can get at a local
computer convention.  Intelligent cards are best if you're running software
like UNIX which allow for multiple user to be attached on multiple serial
lines (a Xenix MICNET for example).

Video adaptors:

This subject turned out to be simpler than I expected (which disappointed me
a little).

The only combinations allowable using standard video adaptors is 1 monochrome
display and 1 color display.

This doesn't mean a MDA-CGA combo only.  It means that any two display 
adaptors will work with each other as long as one is configured for monochrome 
modes only (modes which use memory from B000:0000 to B7FF:000F) and the other 
is configured for color modes only (modes which use anything other than
B0000:0000 to B7FF:000F).  But, don't expect two EGA or two VGA adaptors
configured as above to work because both use special video BIOS routines that
may reside at the same memory locations (usually C000 to C7FF).

Also, Hercules cards will work in conjunction with a color card as long as
the Hercules card is configured to use the first 32 KB of memory; restricting
it to monochrome text mode since Hercules graphics requires both 32 KB pages
of memory.

Special video adaptors do exist that support multiple displays.  All I can
say is that you'd have to shop around.

Disk controllers:

The word is no.  Standard disk controllers, which includes most MFM (ST-506),
RLL, ESDI, and some SCSI, will not operate in multiples unless they're de-
signed to.

Western Digital's 7000FASST2 SCSI host adaptor can be configured as a second-
ary controller.  I also believe that Western Digital's WD1003A MFM controller
can be configured as a secondary controller as well.

Well, I hope all this info is helpful.  I also hope I didn't goof up any of
the information I got.

Any corrections, comments, additional info, or comments are greatly appre-
ciated.

Thanks.

Thank you and happy hunting!		Actually: Ethan M. Young
"If Linus looked like Worf, would you	Internet: fargo@iear.arts.rpi.edu
 try to take his blanket away?"		Bitnet (??): usergac0@rpitsmts.bitnet
	- dorsai@pawl.rpi.edu		Disclaimer: Who said what?