AMD builders...valuable info, read!
Running the new 266FSB Athlons in KT133 MBs
The new 266MHz Front Side Bus ( FSB ) parts will boot in a KT133 MB, however they will come up as a lower speed Athlon processor than they are marked.
The reason for this is the Athlon processors use the FSB Clock provided by the MB,and multiply it up by fixed multiplier inside the chip. The FSB Clock is 100MHz in the case of the KT133 MBs and 133MHz in the case of the KT133A and AMD 761 MBs. Take a 1GHz/266FSB Athlon for example. This part would have a 7.5X mulitplier since 133.33MHz X 7.5 = 1.0GHz. If this part were to be plugged into a KT133 MB with an FSB Clock of 100MHz it would boot up as a 7.5 X 100MHz = 750MHz Athlon. Not a good deal. Hence, the new 266FSB Athlons must be used in KT133A or AMD 761 MBs that have the ability to run with a 133MHz FSB Clock.
Incidentally, the 200MHz and 266Mhz FSB number comes from the FSB Clock multiplied by the Double Data Rate of the FSB of 2. 100MHz FSB X 2 = 200MHz Data Rate and 133MHz FSB X 2 = 266MHz Data Rate.
A 1133MHz/266FSB Athlon in a KT133 MB would come up as an 8.5 X 100MHz = 850Mhz
Athlon and a 1.2GHz/266FSB Athlon in a KT133 MB would come up as a 9.0 X 100MHz = 900MHz Athlon.
200MHz FSB Athlons will run in the new KT133A & AMD 761 MBs since all KT133A & 761 MBs can run at either 100MHz FSB or 133MHz FSB. However, 200MHz FSB Athlons will not run in KT133A or 761 MBs with their FSB Clocks set to 133MHz.
Lastly, the way to tell the difference between a 200MHz FSB Athlon and a 133MHz Athlon is by looking at the part number which is on second line on the chip. The 200MHz parts have a B at the end of the part number whereas the 266MHz parts have a C at the end of the part number. Further information regarding interpreting the part number may be found in the Athlon and Duron Data Sheets in the Ordering Information Section. These data sheets may be obtained from the AMD website at http://www.amd.com .
