28 Mar
2001
28 Mar
'01
4:19 a.m.
There should be a dipswitch on the board. By means of this dip-switch you can
configure the type and the amount of RAM on the board. But you would need
the data on the dipswitch. Various 286-boards had different ways to use the
dipswitches. I wonder what kind of RAM you put on it, like banks of 8*(256k*1),
8*(1m*1), 2*(256k*4) these all DIL-chips or ... SIPPs. Only very late 286-boards
allowed for 30-pin SIPPs (almost identical to 30-pin SIMMs, but with leads
rather
than edge contacts)
12Mhz CPU-clock sounds right to me if the oscillator was 24Mhz.
The turbo switch should be connected to a 2-pin header on the board
in order to change the clock between 12Mhz or 6Mhz (the original IBM AT
speed). A turbo-led connector should also be present this being connected
to a fancy dual 7-segment display module that could be jumper-configured
to any two settings like HI-LO of 12-06 or any creative display that you would
fancy.
Sometimes the turbo-speed could be software-switched with <ctrl> <alt>
<+>
to set to turbo or toggle the speed and <ctrl> <alt> <-> to set to low
speed
(the + and the - on the numerical keyboard that is)
Just try some .....
Sipke de Wal
-----------------------------------------------------------------
http://xgistor.ath.cx
----- Original Message -----
From: Mario Premke <mapr0003(a)stud.uni-sb.de>
To: <classiccmp(a)classiccmp.org>
Sent: Tuesday, March 27, 2001 10:04 AM
Subject: Re: i286-Mainboard
a
at
board
> I hope you've tried the obvious, e.g. <F1> or <DEL> during the POST
sequence
to
> enter BIOS setup? The earliest PC/AT's used
a setup diskette to do the
setup of
the CMOS-based
parameters. That may prove to be a problem.
Yes, I get into the CMOS-Setup, but in there I cannot change the values
for memory and when I switch the power on the BIOS only tests the first
640Kb of memory ...
> To start out, I'd leave the "turbo" switch alone. However,
there's usually > Turbo indicator LED that will tell you when
you're in TURBO mode. If
there's no
> TURBO button, there's probably a jumper
connection available somewhere, and
> these connections are normally located in the lower left region of the board
> (assuming the power and keyboard connections are at the upper right, for
> reference. When you say "not available" do you mean you don't have
one, or
that
it's not
present/supported on the motherboard?
I put the board into a modern AT-Box - there's no turbo button or
turbo-LED.
> I'm curious about one thing ... Why is it that you believe it to be operable
12 MHz? Is
the CPU marked as such? Can you tell anything about the support
chip set? I vaguely remember something about a Morse '286 around here
The clock on the board shows 24Mhz, so I assume the the CPU works at
12Mhz. I don't have the board right here and I cannot remember what chip
set is used.
> someplace. It's possible that there's a manual, but more likely it's a
that was hying
about. I may not have it anymore, but you never know ...
There's a web-site mentioning the board, but the link to some manuals is a
dead link :-(((
Cheers,
Mario