Re: [Gumstix-users] Question about memory speed/bus width

[Dave H. <dhy...@gm...>]

Hi Craig,

> My quick mental arithmetic suggests that your CPU is running at 200MHz,
> even if it's a 400MHz part.  Check dmesg to see what the CPU is being
> clocked at.  If it's only 200MHz, then you can use the "userspace"
> cpufreq governor to speed it up to 400MHz.  Actually, I need to rework
> some of the data in the cpufreq tables I think -- it seems to tend to
> prefer lower memory bus frequency even when using the performance
> governor for some reason.  I used to be able to clock a 200MHz CPU at
> 133x4 but this seems to not be working right any more.  But anyway,
> memory connects directly to the PXA bus on the gumstix, and the RAM
> part can go up to 133MHz.

OK. Here are the frequency related things from dmesg....

Calibrating delay loop... 397.31 BogoMIPS

PXA CPU frequency change support initialized
Verified CPU policy: 398131Khz min to 398131Khz max
Verified CPU policy: 398131Khz min to 398131Khz max
Changing CPU frequency to 398 Mhz, (SDRAM 49 Mhz)

I found some stuff in /sys/devices/system/cpu/cpu0/cpufreq/
If I do

for f in *; do echo ===== $f =====; cat $f; done

I get this output:

===== cpuinfo_max_freq =====
530842
===== cpuinfo_min_freq =====
99533
===== scaling_available_governors =====
powersave userspace performance
===== scaling_cur_freq =====
398131
===== scaling_driver =====
PXA25x
===== scaling_governor =====
powersave
===== scaling_max_freq =====
398131
===== scaling_min_freq =====
398131
===== scaling_setspeed =====
398131

I tried this:

# echo "performance" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
Verified CPU policy: 398131Khz min to 398131Khz max
Verified CPU policy: 398131Khz min to 398131Khz max
Changing CPU frequency to 398 Mhz, (SDRAM 49 Mhz)
Changing CPU frequency to 398 Mhz, (SDRAM 49 Mhz)
# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
powersave

but it doesn't seem to stick (I also tried "usermode" with the same
results. Neither one made any difference in the squeak benchmark.

The 49 MHz for the SDRAM seems a little low?

Is the memory 16 bits or 32 bits wide?

Thanks

-- 
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/