From: drew@caesar.cs.colorado.edu (Drew Eckhardt)
Subject: Re: Advice sought on installing 386 motherboards into ATs
Organization: University of Colorado at Boulder
Date: Tue, 7 Apr 1992 06:26:02 GMT

In article <1992Apr7.050951.2490@reed.edu> nelson@reed.edu (Nelson Minar) writes:
>My poor little AT clone is near useless now. I really need the memory
>management features of the 386 chip to get anything useful done (read:
>run Linux).
>
>How much do 386 motherboards cost? Obviously I want to get a fast one,
>but I'm not wealthy.

sx boards can be found for under $200 with CPU, 33Mhz DX boards for under
$300 with CPU.  Of course, you can buy more expensive boards, but 
chip prices keep them from being much cheaper.  

Right now, I'm not looking to buy any hardware beyond a couple of 8088's and 
support chips for some custom hardware, and consequently haven't looked for 
anything lately, so don't bother asking where.  

The only thing I will say about "where" is that sometimes you can 
get local shops to deal very competitively with mail order if 
you apply the right amount of arm twisting while still being 
pleasant....

>Are there major differences between the various cheap 386 boards?
>

Yes.  The way shadow RAM is handled differs.  Some chipsets say,
"Hey, the 384K of RAM from 640K to 1M is mine weather I use it or not", 
others will use what they need for shadowing ROM, and map the rest up 
to the end of memory where it can be used as extended memory. 
This can make a difference of 300K in available memory.

Cache size, and weather certain regions can be marked non-cacheable,
available memory slots (number, location (will
they interfere with expansion cards?, wether they take 4M simms 
or not,etc), BIOS setup (some BIOS's have a setup
disk rather than a setup program in ROM), etc are all important.

>Can I just drop the 386 board into my AT case and still use the same
>power supply, disk controller, keyboard, and EGA card?

In most cases, yes.  Some very old hardware doesn't like 
running at faster bus speeds - but most recent stuff is OK.
Also, if you have a non-standard case, this won't work.  Finally,
keep in mind that there are two sizes of motherboards : 
"baby", or 
	
XT formfactor (fits just about anything with a standard 8 slot
case), and fullsize.
>Will I need to buy new ram or can I use my 80ns drams?

Maybe.  Most modern motherboards take SIMMs, whereas 
older hardware took DIPs.  If you have DIPs, you are probably 
out of luck.  Aside from that, speed is an issue.  Some fast
(33,40 Mhz) 386/486 boards will not run reliably with 1 
wait state on a cache miss using only 80ns RAMs.  Others will. Again, 
this will depend on the RAMs in question as well as the motherboard.

Also, remember that no matter what happens you must have memory 
in word width units - IE in an SX box, memory must be added 
in chunks of 16 bits or 16 bits + parity (as with your AT.)
In a 32 bit system (full dx or any 486), you add memory
in chunks of 32 bits plus parity.  You may need 
more memory to satisfy this requirement.

>Is the installation easy or should I pay someone?

If you know how to use a screwdriver, don't shuffle your feet and 
then touch the pretty little traces, and can match the connectors  on the 
wires to the ones on the board according to the pinouts in the 
motherboard manual, you're fine.