Re: Udelay and new CPUs

From: Jeremy Fitzhardinge (jeremy@goop.org)
Date: Fri Jan 21 2000 - 18:18:28 EST


On 21-Jan-00 H. Peter Anvin wrote:
> Jeremy Fitzhardinge wrote:
>>
>> On 21-Jan-00 H. Peter Anvin wrote:
>> > There are no "x86 cycles" on Crusoe, so it counts VLIW cycles. In
>> > fact, on TM5400 it counts *nominal* cycles, since the actual cycle
>> > length is variable (due to LongRun).
>>
>> So RDTSC is useless for getting consistent udelay delays.
>>
>
> No, on the contrary. For a 700 MHz TM5400 the TSC will always count at
> 700 MHz even if the CPU decides that it currently only needs to run at,
> say, 175 MHz.

Apparently if you *emphasize* words, they become invisible to my eyes.
Sigh, maybe I should start reading with my lips moving...

        J

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/



This archive was generated by hypermail 2b29 : Sun Jan 23 2000 - 21:00:27 EST