IBM Vintage PCs  S T A T S 
These charts had been drawn from
the IBM Vintage PCs table, which
includes only "family one" (PC/XT, PC/AT) and PS/2
systems, but here PS/1s and PS/VPs, which were introduced in
1992, have also been kept into account. Fastest available systems
have been taken into consideration.
Of course, calculating CPU speed is ... see my remarks on
benchmarks.
For references please check my fastest
available IBM PCs table.
Processor Speed
Gross Processor Speed I submit here that each x86 CPU is twice as fast as the previous one (thus a 386 is two times faster than a 286, which in turn is two times faster than a 8088). These values have been multiplied by each processor's actual clock speed. Of course, this esteem is very gross (for instance, it is known that a 386 CPU offers little advantages over a 286 at the same clock when executing 16bit code). 

Processor Speed in
Dhrystones Source: CheckIt version 2.01. This implementation of dhrystone is 16bit (otherwise it wouldn't run on 8088s and 286s). 

Processor Speed in
relative MHz Source: Landmark version 2.0 (also 16bit). CPU throughput is given in equivalent 286Mhz. 
IBM, XT, AT, PS/1, PS/2, and PS/VP are trademarks of International Business Machines Inc.