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_at_stud.uni-sb.de>
To: <classiccmp_at_classiccmp.org>
Sent: Tuesday, March 27, 2001 10:04 AM
Subject: Re: i286-Mainboard
>
> > 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
a
> > 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
at
> > 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
board
> > 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
>
Received on Wed Mar 28 2001 - 12:19:35 BST