IBM PS/1 Change FSB

Discussion about old PC hardware.

IBM PS/1 Change FSB

Postby HoneyBadger1650 » 2018-3-06 @ 23:54

Hey all,
Another question regarding the AMD 5x86 133 in my PS/1. I've recently installed 256kb of L2 cache in my board, and I'm still yearning for a little bit more speed from this machine. After running Cachchk (v4), I saw that my CPU was only running at 100.2 MHz whereas it's supposed to be at 133 MHz. I know that this is due to my FSB being set incorrectly, but that's just it - I can't for the life of me figure out how to change the speed of it. I've looked all over the board and can't find any jumpers for changing the multiplier. I looked on this website and found the jumper configuration (http://stason.org/TULARC/pc/motherboard ... -TYPE.html), but even on there I didn't see the FSB settings. Only the CPU types (or is that what I need?). I've seen on an older thread that you can change the FSB speed without jumpers (through SETMUL), but that's only for newer CPU's, so it won't work in my situation. Is there a piece of software like that for older CPU's such as this one? I've also seen that someone modified their board to change the speed of the FSB, but there's got to be a better way to go about doing this than physically modifying my board. There aren't any settings in the BIOS for changing the speed either, and that's the first place I thought they would have been. Please let me know if I need to upload pictures.
(CPU is a PNY Quickchip 5x86 133)
Thanks in advance!
HoneyBadger1650
Newbie
 
Posts: 12
Joined: 2017-9-22 @ 18:21

Re: IBM PS/1 Change FSB

Postby FGB » 2018-3-08 @ 02:31

You can't change the FSB with a jumper, you have to replace the oscillator for that purpose BUT the chipet is specified for max. 33MHz.
In reality, you don't want to change the FSB for the 133MHz AMD CPU, because it already runs at 33MHz!
The problem is that the board runs at the CPU's default multiplier which is 3. 3* 33.3 = 100MHz.
The AMD CPU needs the multiplier to be changed to 2 and 2 will be interpreted internally as 4.
This is not possible with this board until you apply a wire-mod to the socket.

The PNY Quickchip does have jumper for the multiplier changem set them to 2 / 4.

Good luck and have fun with the IBM!
www.AmoRetro.de Visit my huge hardware gallery with many historic items from 16MHz 286 to 1000MHz Slot A. Includes more than 80 soundcards and a growing Wavetable Recording section with more than 300 recordings.
FGB
Oldbie
 
Posts: 553
Joined: 2011-6-08 @ 07:27
Location: Germany

Re: IBM PS/1 Change FSB

Postby HoneyBadger1650 » 2018-3-08 @ 22:32

Thanks for your reply!
Could you elaborate on what a "wire-mod" is and what I'd need to do?
I've looked on the CPU, and I don't see any jumpers on it. Only DIP switches for controlling write-back and write-through modes (or is that what you were talking about?)
HoneyBadger1650
Newbie
 
Posts: 12
Joined: 2017-9-22 @ 18:21


Return to General Old Hardware

Who is online

Users browsing this forum: CkRtech, RetroBoogie and 10 guests