Messages in this thread | | | Date | Fri, 24 Aug 2001 09:59:39 -0400 | From | "Christopher Friesen" <> | Subject | Re: [PATCH] (comments requested) adding finer-grained timing to PPC add_timer_randomness() |
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Gabriel Paubert wrote:
> No, both the RTC and the decrementer count nanoseconds, except that the 7 > LSB are not implemented because the timebase clock should have a period of > 128 ns (7.8125 MHz, but according to Takashi Oe, many 601 systems did not > bother to provide the exact frequency and are off by 11 parts in 4096 or > so). As such the LSB can't be used to estimate randomness and the value > must be shifted right by 7. So you need some conditional code (or boot > time patching). At this point you can throw in the high order part > (RTCU/TBU) for additional randomization (RTCU changes much faster on 601, > once per second, than on the other processors).
Have you got any links to information on boot time patching?
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