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From: sl@van-bc.UUCP
Newsgroups: comp.unix.xenix
Subject: Re: Wanted: Suggestion for 286==>386
Message-ID: <1595@van-bc.UUCP>
Date: Fri, 4-Dec-87 04:58:27 EST
Article-I.D.: van-bc.1595
Posted: Fri Dec  4 04:58:27 1987
Date-Received: Thu, 10-Dec-87 01:01:09 EST
References: <7560@eddie.MIT.EDU>
Reply-To: sl@van-bc.UUCP (Stuart Lynne)
Organization: Public Access Network, Vancouver, BC.
Lines: 91
Keywords: 286 upgrade 386 inboard cheap-386 tofu

In article <7560@eddie.MIT.EDU> mdc@eddie.MIT.EDU (Marty Connor) writes:
>
>I am seeking advice from folks in the community about how to best
>upgrade my AT clone to a 386.  I want to start a news distribution
>service, and hacker haven in the Boston Area.
>
>Here's what it currently looks like.
>
>	Wyse 286 (10 mhz) (640k)
>	Intel Above board (4 meg)
>        4 port Digiboard serial card on COM2:
>        1 port serial card on COM1:
>	40 meg hard drive (primary)
> 	20 meg hard drive (secondary)
>
>I would like to turn this into a 386 box.

>If you have any other ideas or advice, please feel free to give
>them... ("I am as you humans say, 'all ears'").
>

One option that I'm looking at is a 386 AT mother board. There seem to be
several available (Intel, Mini 386 from Taiwan, etc). 

These typically have either 32 bit slots for the 32 bit memory or room for
memory on board. For example the Intel mother board has .5MB on board with
two slots, 2 and 8 MB cards are available (although the 8's are very
pricey). The Mini 386 has no 32 bit slots but allows 1/2/4/8 MB on board by
using 4/8 256kb or 4/8 1MB SIM Strips.

These machines are very fast, (Intel 16Mhz 1 wait state, Mini 386 16Mhz 0
wait states) when accessing the 32 bit memory. But they are typically much
slower accessing 16bit memory. So if you're running Unix you don't want to
use anything but 32 bit. 

As an example a 32 bit read on the Intel mother board will take either 187.5 
or 312.5 nano-seconds depending on whether the data is coming from a "busy" 
bank. This is compared to a 32 bit read from 8 bit memory taking 1000 nano
seconds, and from 16 bit memory taking 3125 nano seconds (this is from the
Intel manual, personally I'm convinced that it's probably 1000 for 16 bit
and 3125 for 8 bit, but then who am I to argue :-) ).

In theory you should be able to take any 286 AT and simply replace the
mother board using all of your existing hardware and software. If you wish
to run Unix then you will want additional 32bit memory (2MB minimum).

Guestimates on cost: Intel about $1400 for motherboard, $800 for 2MB memory
card. Mini 386 about $1020 for a 1MB board. Upgrade to 2MB is inexpensive
($200), to 4 or 8MB is quite expensive ($1200/$2400, if you can get the 1MB
SIM's).

I'm currently using the Intel board in a Bell Tech machine at work. We are
fairly happy with it using Microport System V/386. It certainly run's rings
around my little Callan ( 10Mhz 68010 ) here at home. The Mini 386 would
probably be a little faster due to 0 wait state for interleaved memory
access.

We just did some tests tonight on loading down a dumb serial card (vintage
1983 Hostess 8 port card). Basically terminal I/O for a couple of terminals
at 19.2 was fine. One trailblazer at 19.2 was fine as long as nothing much
else was happening (on the other serial ports). I don't think there would 
be any problem with up to four 2400 uucp links although I won't be able to 
test that until next week. 

I don't know yet where the problems with multiple high speed uucp links
lies. It's probably lost characters due to interrupt loading, but could be 
lack of clists to put the incoming data. With two 9600 and one 2400 uucp
links going there was not a whole lot of processor power left :-)

If it is simply processor loading I'm not to sure that it might be curable
by a better driver design. One test showed that we could cause an incoming
uucp link at 9600 to loose characters simply by cat'ing a small file to a
screen (on a lower port number). That is simply bad design, a driver should
always give priority to incoming data if it can. 

If you are going to really load down the system with serial I/O you should
look at a smart card. We've got the Bell Tech ICC card and after some
initial teething problems with the modem control software which they have
almost got fixed (the remaining problems are fairly obscure for low speed
links, with the only serious problem being supporting high speed modems).
They are aware of the problems and have promised a to get a working version
in short order. I like this card and it now works very well for terminals
and low speed modems (up to 2400 bps tested). Given their low cost (about
50% more on a per port basis than most dumb cards) they are a pretty good
deal. 




-- 
{ihnp4!alberta!ubc-vision,uunet}!van-bc!Stuart.Lynne Vancouver,BC,604-937-7532