Phase 0 devices just running @100MHz?

[Siarhei Siamashka]

On Friday 09 March 2007 11:07, pHilipp Zabel wrote:
> On 3/8/07, Nils Faerber <nils.faerber at kernelconcepts.de> wrote:
> > Pierre Hébert schrieb:
> > > It doesn't seem so bad : my s3c2440 at 400MHz shows 199bogomips, so at
> > > 200MHz 100bogomips seems correct (s3c2440 has the same cpu as s3c2410).
> > > I don't know if the bogomips indication is a value in which we can
> > > really trust, these little devices are really efficient even at
> > > 100/200bogomips.
> >
> > The bogomips result is a little different depending on the core
> > architecture. So for the Samsung CPU bogomips ~= 1/2 MHz.
> > OK, good to know!
> > A PXA270 I have on my desk has the ~ 1:1 bogomips to MHz mapping...
>
> I guess this depends on how many cycles the __delay(loops_per_jiffy) loop
>
> ENTRY(__delay)
> 	subs	r0, r0, 1
> 	bhi	__delay
> 	mov	pc,lr
>
> takes on the given cpu.
> On the S3C2440 subs takes 1S and bhi takes 2S+1N cycles.
> Is information about the PXA27x instruction cycle times available
> somewhere?

If you are interested in estimating cpu clock frequency, you can try a simple
test program I have written some time ago:
http://ufo2000.xcomufo.com/maemo/testfreq.c


A few references related to arm cpu performance.

Instruction timings and optimization guide for ARM9E: 
http://arm.com/pdfs/DDI0222B_9EJS_r1p2.pdf
Instruction timings and optimization guide for ARM11 (used in OMAP2): 
http://arm.com/pdfs/DDI0360C_arm11mpcore_r0p3_trm.pdf
Instruction timings and optimization guide for Intel XScale: 
http://download.intel.com/design/int...e/27347302.pdf
Instruction timings and optimization guide for Cortex (used in OMAP3): 
http://arm.com/pdfs/DDI0337C_cortexm3_r1p0_trm.pdf

Comparison of ARM7 and ARM9: http://arm.com/pdfs/comparison-arm7-arm9-v1.pdf
Comparison of ARM9 and Cortex: http://arm.com/pdfs/13128.pdf