High-end AVR vs. low-end ARM?

[Database Administrator]

>>> The LDRHs take 7 cycles (6 + 1), the MLAs take 6 cycles, or in total 26
>>> cycles.
>>> That is exactly twice as slow as AVR32 on the above code. So the claim
>>> of 11
>>> times slower is a total lie. Those Atmel marketeers should be ashamed of
>>> themselves.
>>>
>>
>>
>> And you are comparing 3 MACs with 6 MACs.
>>
>> 6 MACs from memory using AVR32 = 13 clocks.
>> 6 MACs from memory using CM3 = 52 clocks or 4 x difference.
>
>
> No, read again. It's 13 cycles to do 3 MACs, so 26 to do 6 MACS.
>
> Wilco
>


OK,
I see that now, where do you check for saturation?

--
Best Regards,
Ulf Samuelsson
This is intended to be my personal opinion which may,
or may not be shared by my employer Atmel Nordic AB

[Database Administrator]

"Ulf Samuelsson" wrote in message news:gfkcrn$7jm$1@aioe.org...
>>>> The LDRHs take 7 cycles (6 + 1), the MLAs take 6 cycles, or in total 26 cycles.
>>>> That is exactly twice as slow as AVR32 on the above code. So the claim of 11
>>>> times slower is a total lie. Those Atmel marketeers should be ashamed of
>>>> themselves.

>>> And you are comparing 3 MACs with 6 MACs.
>>>
>>> 6 MACs from memory using AVR32 = 13 clocks.
>>> 6 MACs from memory using CM3 = 52 clocks or 4 x difference.
>>
>>
>> No, read again. It's 13 cycles to do 3 MACs, so 26 to do 6 MACS.

> OK,
> I see that now, where do you check for saturation?

There is usually no need to check for saturation unless you have 16-bit
ADC's (rare). With saturation it would be 32 cycles.

Wilco

[Database Administrator]

"Wilco Dijkstra" skrev i meddelandet
news:7RkTk.45327$nA3.22941@newsfe03.ams2...
>
> "Ulf Samuelsson" wrote in message
> news:gfkcrn$7jm$1@aioe.org...
>>>>> The LDRHs take 7 cycles (6 + 1), the MLAs take 6 cycles, or in total
>>>>> 26 cycles.
>>>>> That is exactly twice as slow as AVR32 on the above code. So the claim
>>>>> of 11
>>>>> times slower is a total lie. Those Atmel marketeers should be ashamed
>>>>> of
>>>>> themselves.
>

So the AVR32 inner loop is only 2-3 x faster than the Cortex-M3.
Yes, noone in their right mind would switch for such¨
a meagre performance increase ;-)

>>>> And you are comparing 3 MACs with 6 MACs.
>>>>
>>>> 6 MACs from memory using AVR32 = 13 clocks.
>>>> 6 MACs from memory using CM3 = 52 clocks or 4 x difference.
>>>
>>>
>>> No, read again. It's 13 cycles to do 3 MACs, so 26 to do 6 MACS.
>
>> OK,
>> I see that now, where do you check for saturation?
>
> There is usually no need to check for saturation unless you have 16-bit
> ADC's (rare). With saturation it would be 32 cycles.
>
> Wilco
>


--
Best Regards,
Ulf Samuelsson
This is intended to be my personal opinion which may,
or may not be shared by my employer Atmel Nordic AB

[Database Administrator]

"Ulf Samuelsson" wrote in message news:gfkp5n$pjh$1@aioe.org...
>
> "Wilco Dijkstra" skrev i meddelandet
> news:7RkTk.45327$nA3.22941@newsfe03.ams2...
>>
>> "Ulf Samuelsson" wrote in message news:gfkcrn$7jm$1@aioe.org...
>>>>>> The LDRHs take 7 cycles (6 + 1), the MLAs take 6 cycles, or in total 26 cycles.
>>>>>> That is exactly twice as slow as AVR32 on the above code. So the claim of 11
>>>>>> times slower is a total lie. Those Atmel marketeers should be ashamed of
>>>>>> themselves.
>>
>
> So the AVR32 inner loop is only 2-3 x faster than the Cortex-M3.
> Yes, noone in their right mind would switch for such¨
> a meagre performance increase ;-)

Actually the worst case is 2.5x, but as steve said earlier, actual measurements
taking flash speed etc into account are closer to 1.5x. Either way, that's not
close at all to the claimed 11x difference.

For better DSP performance and more MHz most people would use ARM9E
instead (it's used in many harddrives).

Wilco