Pentium II CPU upgrading to Pentium III ???

A friend of mine has this old computer with a Jetway 720BF motherboard, 64MB
of 168pin 100MHz SDRAM and a Pentium II (Slot 1) CPU (100MHz FSB) with
450MHz installed. The computer still does the job but I was wondering if it
would be possible to tweak the thing a little bit. According to the manual
the motherboard supports Pentium II and III CPU's up to 500MHz. Now I know
it would not make much sense to upgrade to a 500MHz from a 450 so I was
wondering if it would be possible to chuck a Pentium III CPU in with say
1000MHz? The manual does not say you can but by the time of writing how
could it? So my question is, is there any difference between a Pentium III
500 and a Pentium III 1000???? Will that motherboard support the 1000 MHz
CPU? Or is there some significant differences in the later Pentium III
CPU's? Unfortunately the webpage from Jetway is not too helpful either. For
those who care to check:
http://www.jetway.com.tw/evisn/produ...20bf/720bf.htm

Memory4less as an example sells Pentium III CPU's
http://www.memory4less.com/cpus/m4l_pentium3.asp

The motherboard also supports up to 1.5 GB of RAM (which seems really
excessive!) and I was thinking of chucking an additional 128 or maybe 256 MB
of RAM in there to speed things up a little.

What are your opinions???

Thanks heaps in advance

Hans