The KT266A is a VIA motherboard chipset,http://en.wikipedia.org/wiki/List_of_VIA_chipsets#Slot_A_and_Socket_A
The motherboard chipset for your motherboard, consists of a Northbridge, and Southbridge chip.
The Northbridge is a VIA 8366A
The Southbridge is a VIA VT8235http://en.wikipedia.org/wiki/File:Motherboard_diagram.svg
CPU = Central Processing Unit. Another term used is Microprocessor, or Processor for short ]
The Northbridge chip handles the faster capabilities of a computer.
Handles the Processor, Ram Memory, and HIGH-speed graphics.
[A graphics card installed into a PCI expansion slot is Not high-speed graphics.
Integrated Graphics is Not high-speed graphics.
AGP and PCI Express are high-speed graphics.
If you have an AGP graphics expansion slot, it is handled by the Northbridge chip.
If you have a PCI Express expansion slot, it is handled by the Northbridge chip ]
The Southbridge chip handles the slower capabilities of a computer. This is shown in the diagram.
The VIA KT266A's Northbridge chip, (VT 8366A) supports AMD processors with UP TO a 266MHz Front Side Bus.
In the chart you see under the FSB heading -> 100 - 133MHz
100MHz to 133Mhz.
AMD processors are 'Double-Pumped'.
Therefore 133MHz becomes 266MHz.
233Mhz with the jumpers at their present positions?
Looking at the motherboard, as it is mounted in the computer case; Processor to the Top, Ram Memory slots to the Right,
5 White PCI slots to the Bottom;
The J4 jumper is above the CMOS battery.
The CPU Frequency Select jumper.
(The J1 jumper is right next to the CMOS battery. To the left. That is the Clear CMOS jumper)
The jumper has 3 pins. Number 1 pin is on the LEFT.
From Left to Right; Pins 1, 2, and 3.
With a jumper block,http://en.wikipedia.org/wiki/File:Jumperblock-shunts.jpg
,on Pins 1 and 2, you have a 100MHz FSB.
With a jumper block on Pins 2 and 3, you have a 133MHz Front Side Bus.
Processor you pick have a broken pin?
You can use AMD Athlon processors with up to a 133Mhz FSB, or AMD Duron processors with up to a 133MHz FSB.
[Actually 200MHz FSB, and 266MHz FSB. Remember what I stated about Double-Pumped ]
Here is a link to a free User Manual, for the Syntax SV266A motherboard,http://www.scribd.com/doc/41762039/Manual-Sv266a
(Just keep scrolling down)
For additional questions please post in a Comment.