pito:
Ie. dallas (now maxim) 89c450 (33MHz one clock per machine cycle) has got a built in bootloader (via the uart). Works fine.
PS: above chip is half of the atmega328p performance clock to clock. Why do you need 8051 then?
I messed with the DIL 40pin 89C450. Programming via built in bootloader (serial 115k2 uart). So very breadboard friendly. Wrote some C code (fp trig math test) to benchmark (Keil).
MHz Elapsed us mA
1284p Arduino 16 845 -
89C450 Keil C51 32 1317 81 (5V)
So you may see the 51's architecture is really not much C friendly. The C450 is 3.1x slower clock to clock when doing fp math.
The only positive stuff I saw was the Keil and IAR support banking of memory (flash and sram) with C, so you can write ie. xMBytes large C code which requires yMBytes of ram and it will work (provided you wired the external flash and sram to the 8051). Interesting.. 