In the '51 world, there is one nice thing - compatibility. There is a zillion of derivatives around, not only having possibly higher clock, but also increasing performance by using a different architecture - simply less clocks per instruction cycle. The "classic" '51 uses 12, as your 'S8252 does. You've mentioned the x2 mode in the 'S8253, which is in fact a 6-clock core with a /2 prescaler which is by default on. There are also 4-clock, 2-clock and 1-clock derivatives around (with 4- and 1-clock having NOT the same number of instruction cycles per instruction as the "classic" '51 has). <shameless advertising>See the overview on my 8052.com homepage</shameless advertising>. And the good news is, that some of the faster ones are pin-compatible drop-in replacements (the legendary Dallas DS80C320, DS89C4x0, the RD2 sub-family). The DS89C4x0 and the RD2's are in-situ programmable via UART, you need no "programmer" etc.

Of course, if you just want to have fun, you can go for the overclocking - buy a bunch of crystals and try increasing the freq. You have been warned more than enough, though... :-)))

Jan Waclawek