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    DateWed, 12 Dec 2007 13:07:47 +1100
    FromNigel Cunningham <>
    SubjectRe: [RFT] Port 0x80 I/O speed
    Rene Herman wrote:
    > On 12-12-07 00:55, Nigel Cunningham wrote:
    > 
    >> (AMD 1.8GHz Turion, running at 800MHz. ATI RS480 - Mitac 8350 mobo)
    >>
    >> nigel@home:~/Downloads$ gcc port80.c -o port80
    >> nigel@home:~/Downloads$ sudo ./port80
    >> cycles: out 1235, in 1207
    > 
    > Looking good.
    > 
    >> nigel@home:~/Downloads$ gcc -O2 port80.c -o port80
    >> nigel@home:~/Downloads$ sudo ./port80
    >> cycles: out 1844674407370794, in 1844674407369408
    > 
    > Obviously not. I suppose this changes with -m32 on the GCC command line?
    > (sorry for missing that, I have no 64-bit machines).
    
    Yes, it does:
    
    nigel@home:~/Downloads$ gcc -m32 -o port80 port80.c
    nigel@home:~/Downloads$ sudo ./port80
    cycles: out 1231, in 1208
    nigel@home:~/Downloads$ sudo ./port80
    cycles: out 1233, in 1210
    
    Incidentally:
    
    nigel@home:~/Downloads$ processor_speed
    
    (A little script I made because my lappy does a solid lock every now and
    then that seems to be cpu-freq related - locking it to one frequency
    makes the lock far less common).
    
    Speed is now 1800000.
    nigel@home:~/Downloads$ sudo ./port80
    cycles: out 2472, in 2505
    nigel@home:~/Downloads$ sudo ./port80
    cycles: out 2489, in 2515
    nigel@home:~/Downloads$ sudo ./port80
    cycles: out 2481, in 2503
    nigel@home:~/Downloads$ sudo ./port80
    cycles: out 2476, in 2507
    So the same effect Maxim reported is seen here.
    
    Regards,
    
    Nigel
    
    
    
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