http://www.rci.rutgers.edu/~preid/pcxtsw.htm
IBM PC
Switch block 1, near center of board:
* Switch 1
* off = Boot from floppy
* ON = Don't boot from floppy (goes to Cassette BASIC in ROM)
* Switch 2
* off = 8087 Math Chip installed
* ON = 8087 NOT installed
* Switch 3,4
* ON,ON = One bank of memory
* off,ON = Two banks
* ON,off = Three banks
* off,off = Four banks
* Switch 5,6
* off,off = MDA (or Hercules) Video
* off,ON = 40 column CGA
* ON,off = 80 column CGA
* ON,ON = No video or special (EGA, VGA)
* Switch 7,8
* ON,ON = 1 floppy drive
* off,ON = 2 flops
* ON,off = 3 flops
* off,off = 4 flops
Switch block 2, near power supply:
Switches 1, 2, 3, 4, 5 = Total memory installed
* Memory installed - sw1 2 3 4 5
* 16K = ON ON ON ON ON
* 32K = ON ON ON ON ON
* 48K = ON ON ON ON ON
* 64K = ON ON ON ON ON
* 96K = off ON ON ON ON
* 128K = ON off ON ON ON
* 160K = off off ON ON ON
* 192K = ON ON off ON ON
* 224K = off ON off ON ON
* 256K = ON off off ON ON
* 288K = off off off ON ON
* 320K = ON ON ON off ON
* 352K = off ON ON off ON
* 384K = ON off ON off ON
* 416K = off off ON off ON
* 448K = ON ON off off ON
* 480K = off ON off off ON
* 512K = ON off off off ON
* 544K = off off off off ON
* 576K = ON ON ON ON off
* 608K = off ON ON ON off
* 640K = ON off ON ON off
* Switches 6, 7, 8
* Always off
Jeffrey H. Ingber (jingber_at_ix.netcom.com)
On Tue, 2002-10-01 at 17:40, Voyager wrote:
> Thanks!
> But, could you please give me more details on the ON-OFF and meaning? for
> example the 1,7,8 is for the number of drives. Up to 8 drives?
>
> ----- Original Message -----
> From: "Fred Cisin (XenoSoft)" <cisin_at_xenosoft.com>
> To: <cctalk_at_classiccmp.org>
> Sent: Tuesday, October 01, 2002 11:40 PM
> Subject: PC SWITCHES (was: DRIVPARM
>
>
> > On Tue, 1 Oct 2002, Voyager wrote:
> >
> > > Please correct me if I am wrong, but on the IBM PC motherboard there
> should
> > > be some jumpers or a dip switch array. Am I wrong? could anybody provide
> me
> > > with the functionality of these jumpers or switches?
> >
> > On the PC, there are TWO switch packs. One for memory size, and one for
> > various option, including number of drives, 8087 installed, etc.
> > On the XT, there is ONE switch pack, and memory is determined during POST.
> >
> > Int 11h maps the switches into AX.
> > Int 12h reports the amount of RAM.
> >
> > 1, 7, 8 are the number of drives
> > 2 is co-processor (half are set wrong)
> > 3, 4 is RAM on motherboard
> > 5, 6 is monitor type
> >
> >
> > --
> > Grumpy Ol' Fred cisin_at_xenosoft.com
> >
>
Received on Tue Oct 01 2002 - 18:31:00 BST