Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops

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On 11-12-07 16:37, Paul Rolland wrote:

Great, thanks for the quick replies.
That last one below especially is quite a bit more than 1. As said before, most hardware isn't in fact going to need anything but I suppose udelay(2) might be the "safer" replacement for the outb then... 


On Tue, 11 Dec 2007 16:28:56 +0100
Rene Herman <[email protected]> wrote:


On 11-12-07 15:15, Rene Herman wrote:


On 11-12-07 14:32, Paul Rolland wrote:
This might be a bit more constant, I suppose. This serialises with cpuid. Don't see a difference locally, but perhaps you do. 
Well, yes, at least on the PIII and the Opteron... Core2 is still changing
a lot...
On a Duron 1300 with an actual ISA bus, "out" is between 1300 and 1600 for me and "in" between 1200 and 1500 with a few flukes above that which will I suppose be caused by the bus (ISA _or_ PCI) being momentarily busy or some such... 


The results :

Core 2Duo 1.73 GHz :
[root@tux tmp]# ./in2
out: 2777
in : 2519
[root@tux tmp]# ./in2
out: 2440
in : 2391
[root@tux tmp]# ./in2
out: 2460
in : 2388


Okayish I guess, especially when subsequent runs stay near those values.

2500/1730 = 1.45 us


Pentium III :
[root@www-dev /tmp]# ./in2
out: 746
in : 747
[root@www-dev /tmp]# ./in2
out: 746
in : 747
[root@www-dev /tmp]# ./in2
out: 746
in : 745


746/600 ~= 1.24 us


AMD Opteron 150 :
-bash-3.1# ./in2
out: 4846
in : 4845
-bash-3.1# ./in2
out: 4846
in : 4846
-bash-3.1# ./in2
out: 4846
in : 4845


4846 / 2400 = 2.02 us

Rene.

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