Answer to: What is a kernel?

[John S Gwynne]

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   In message <m0r0ULp-000CwuC at knuth.mtsu.edu> , you write:
 
| I'm taking Operating Systems right now, just went over semaphores a few
| weeks ago.  We were "told" that semaphore operations (P & V) are pretty
| expensive respect to cpu cycles.  Is that a problem in the real world,
| or is it insiginificant compred to the number of spare CPU cycles
| we've got nowadays (with respect to EFI controllers :)?


ok, I just wanted to use the ADC and semaphore as an example of what the
kernel could do for you. It's one approach I'm considering. Another approach
is to have a remote 68hc8111e2 that will fire data back to the EFI86k over a
serial line. It would be used for the slower changing parameters like air temp,
coolant temp, etc.. My motivation here is the reduction of wires; put the
68hc811 under the hood and the EFI68k in the passenger compartment or trunk
(some place not as hostile). Just another thought to kick around.


As far as semaphores go, the file fact-c020.ps on the server has all 
the timing information for RTEMS.

for the 68020 at 20MHz (time in micro-sec): (EFI69k is 20/12 longer)

semaphore_create		38
semaphore_ident			77
semaphore_delete		49
semaphore_obtain
  available			33
  not available - no_wait 	33
  not available -- block 	85
semaphore release
  no waiting task		35
  task readied - returns to caller 56
  task readied - preempts caller 75

I will incorporate a timer in my version of EFI69k to measure execution times
of the EFI software. From this we can due a scheduling analysis.

                                       John S Gwynne
                                          Gwynne.1 at osu.edu
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