Note that the UNROLL option makes the 'inner' des loop unroll all 16 rounds instead of the default 4. RISC1 and RISC2 are 2 alternatives for the inner loop and PTR means to use pointers arithmetic instead of arrays. IRIX 6.2 - R10000 195mhz - cc (-O3 -n32) - UNROLL RISC2 PTR 496,000 3968k/s solaris 2.5.1 usparc 167mhz?? - SC4.0 - UNROLL RISC1 PTR [1] 475,400 3804k/s solaris 2.5.1 usparc 167mhz?? - gcc 2.7.2 - UNROLL RISC1 PTR 306,000 2448k/s linux - pentium 100mhz - gcc 2.7.0 - assember 281,000 2250k/s NT 4.0 - pentium 100mhz - VC 4.2 - assember 281,000 2250k/s IRIX 5.3 - R4400 200mhz - gcc 2.6.3 - UNROLL RISC2 PTR 235,300 1882k/s IRIX 5.3 - R4400 200mhz - cc - UNROLL RISC2 PTR 233,700 1869k/s NT 4.0 - pentium 100mhz - VC 4.2 - UNROLL RISC1 PTR 191,000 1528k/s DEC Alpha 165mhz?? - cc - RISC2 PTR [2] 181,000 1448k/s linux - pentium 100mhz - gcc 2.7.0 - UNROLL RISC1 PTR 158,500 1268k/s HPUX 10 - 9000/887 - cc - UNROLL [3] 148,000 1190k/s solaris 2.5.1 - sparc 10 50mhz - gcc 2.7.2 - UNROLL 123,600 989k/s IRIX 5.3 - R4000 100mhz - cc - UNROLL RISC2 PTR 101,000 808k/s DGUX - 88100 50mhz(?) - gcc 2.6.3 - UNROLL 81,000 648k/s solaris 2.4 486 50mhz - gcc 2.6.3 - assember 65,000 522k/s HPUX 10 - 9000/887 - k&r cc (default compiler) - UNROLL PTR 76,000 608k/s solaris 2.4 486 50mhz - gcc 2.6.3 - UNROLL RISC2 43,500 344k/s AIX - old slow one :-) - cc - 39,000 312k/s Notes. [1] For the ultra sparc, SunC 4.0 cc -fast -Xa -xO5, running 'des_opts' gives a speed of 475,000 des/s while 'speed' gives 417,000 des/s. I believe the difference is tied up in optimisation that the compiler is able to perform when the code is 'inlined'. For 'speed', the DES routines are being linked from a library. I'll record the higher speed since if performance is everything, you can always inline 'des_enc.c'. [2] Similar to the ultra sparc ([1]), 181,000 for 'des_opts' vs 175,000. [3] I was unable to get access to this machine when it was not heavily loaded. As such, my timing program was never able to get more that %30 of the CPU. This would cause the program to give much lower speed numbers because it would be 'fighting' to stay in the cache with the other CPU burning processes.