Re: [RFT] Port 0x80 I/O speed

[James Kosin <jkosin@intcomgrp.com>]

Rene Herman wrote:
> Good day.
> 
> Would some people on x86 (both 32 and 64) be kind enough to compile and
> run the attached program? This is about testing how long I/O port access
> to port 0x80 takes. It measures in CPU cycles so CPU speed is crucial in
> reporting.
> 
> Posted a previous incarnation of this before, buried in the outb 0x80
> thread which had a serialising problem. This one should as far as I can
> see measure the right thing though. Please yell if you disagree...
> 
> For me, on a Duron 1300 (AMD756 chipset) I have a constant:
> 
> rene@7ixe4:~/src/port80$ su -c ./port80
> cycles: out 2400, in 2400
> 
> and on a PII 400 (Intel 440BX chipset) a constant:
> 
> rene@6bap:~/src/port80$ su -c ./port80
> cycles: out 553, in 251
> 
> Results are (mostly) independent of compiler optimisation, but testing
> with an -O2 compile should be most useful. Thanks!
> 
> Rene.
> 
[root@beta jkosin]# cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 7
model name      : Pentium III (Katmai)
stepping        : 3
cpu MHz         : 499.156
cache size      : 512 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca
cmov pat pse36 mmx fxsr sse
bogomips        : 996.14

[root@beta jkosin]# ./a.out
cycles: out 683, in 299
[root@beta jkosin]# ./a.out
cycles: out 683, in 299
[root@beta jkosin]# ./a.out
cycles: out 683, in 299
[root@beta jkosin]#

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