On Tuesday 09 January 2007 18:33, Lennart Sorensen wrote:
> Then for the next one it does:
> ccr3 = GetCx86(CX86_CCR3);
> setCx86(CX86_CCR3, (ccr3 & 0x0f) | 0x10);
>
> Couldn't that have been:
> setCx86(CX86_CCR3, (getCx86(CX86_CCR3) & 0x0f) | 0x10);
>
> No temp variable, and again it clearly does not intend to restore the
> value again later (even though the bug actually did cause the value to
> be restored by accident).
No, ccr3 should be restored to protect some registers (or at least bit 4
should be cleared in ccr3).
BTW:
In function set_cx86_inc()
[...]
/* PCR1 -- Performance Control */
/* Incrementor on, whatever that is */
setCx86(CX86_PCR1, getCx86(CX86_PCR1) | 0x02);
/* PCR0 -- Performance Control */
/* Incrementor Margin 10 */
setCx86(CX86_PCR0, getCx86(CX86_PCR0) | 0x04);
[...]
This setting is only valid for 200MHz...266MHz CPUs, for 300MHz and 333MHz
CPUs the Incrementor Margin should be 1-1.
There is an AppNote about this setting:
AMD Geode GX1 Processor Memory Timings for Maximum Performance.
Juergen
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