Rtems Benchmarking

Eric Norum eric.norum at usask.ca
Thu Dec 7 14:20:27 UTC 2000

Peter Mueller wrote:
> Hi all,
> I run some of the tm tests on our 68332 board. I want compare the figures
> with the efi332 board, but a look to the bsp shows that there is no code to
> get the timer data. John told me that he don't know how the data was
> produced or who has put the file to the ef332 directory!?
> Our figures are about 1.5 to 3 times larger compared to the gen68360
> board. I'm not sure if this is an error in our timing routines. Has anyone
> experience with 68360 and 68332 CPUs? Does this makes sense?
> Gen68360: 68360 CPU with 25MHz
> OurBoard: 68332 CPU with 16MHz.
> I do not know if the 360 is based on the CPU32 core too, but I think so.
> Only comparing the benchmark figures to the CPU MHz clock rates would give a
> factor of about 1.6 but not 3.
> Any comments?

The 68360 is based on a CPU32+ core while the 68332 is based on a CPU32
core.  Here's a quote from the 68360 User's Manual:

The CPU32+ core is a CPU32 core with its bus interface unit modified to
connect directly to the 32-bit IMB and take advantage of the larger bus
width. Although the original CPU32 core already had a 32-bit internal
data path and 32-bit arithmetic hardware, its external interface (i.e.,
to the internal IMB) was 16 bits. The CPU32+ core, however, can operate
on 32-bit external operands with one bus cycle. This capability allows
the CPU32+ core to fetch a long-word instruction or two word-length
instructions in one bus cycle, allowing the internal instruction queue
to be filled more quickly. The CPU32+ core can also read and write 32-
bits of data in one bus cycle. The CPU32+ has an additional word in its
instruction pipeline when fetching from a 32-bit port. When fetching
from a 16-bit port, this additional word is disabled. The performance of
the CPU32+ on a 16-bit bus is the same as the CPU32 per-formance.

So I'd expect quite a bit higher performance from the 68360.  Any
application which is limited by bus speed will get a 2X boost from the
wider data path.

Eric Norum                                 eric.norum at usask.ca
Department of Electrical Engineering       Phone: (306) 966-5394
University of Saskatchewan                 FAX:   (306) 966-5407
Saskatoon, Canada.

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