[Coco] 6809/6309 Power Analysis

[Stephen Adolph]

I gotta say, I think this can be a challenge to define, let alone measure.

Certainly there is the dynamic supply power that is feeding the
toggling gates.  This is coming from the main supply.  I would just
measure the power on the main lead.

But, there is also power related to I/O.

I'm sure there is an industry standard technique and definition of
what and how to measure this, but I'm not aware of it.

I would probably just do the main supply lead and assume it is the
majority of the power.

...Steve

On Thu, Jan 21, 2010 at 4:54 PM, Boisy G. Pitre <boisy at tee-boy.com> wrote:
> Calling all hardware/electrical engineering gurus on the list...
>
> As some of you know, I am working on my thesis this semester where I am exploring power-aware compiler optimizations.  I've selected (surprise) the 6809/6309 as my evaluation processor and will be retooling RELIC to use the power information that I am attempting to gather to make decisions about instruction use based on the current that they draw.
>
> I'm hoping you hardware gurus can give me some input on the measurement part, in which I am attempting to determine the current draw of the 6809 when executing specific instructions.  The absolute value is not important; it is the relative difference of current draw for different instructions that I need to move forward.
>
> Just to give you an idea of the type of equipment that I have access to at the UL campus:
>
>        - Agilent Technologies MS06104A Mixed Signal Oscilloscope with analog probes as well as two 54620-61601 8-wire Logic Analyzer probe cables
>        - Agilent Portable Logic Analyzer, don't have the exact model number but looks like a microwave oven and I am told costs around $55K.
>
> The ideas brought up so far for measuring current at the instruction level:
>        - use a PIC with an A/D convertor to measure the voltage.
>        - use a shunt resistor (james recommended this method to me as well in private email) to measure current and outlined here: http://jet-server.commtest.co.nz/kb2/11624.htm
>
> On the software side, I have constructed several test executables that run under NitrOS-9 and execute a particular instruction over and over (with interrupts masked of course). The baseline measurement instruction is CWAI, which puts the processor in sleep mode.  The code looks something like this:
>
>    cwai #^IntMasks
>
> With interrupts masked there should be no activity and the cwai should put the processor to a wait mode.  I would then take the measuring device of choice and measure the current for a fixed amount of time (say 1 second).
>
> Afterwards, I would run the following program which has a series of 100 MUL instructions (MUL is chosen for presumably higher use of CPU):
>
>     ldd       #$0000
>     orcc     #IntMasks
> toploop:
>     mul
>     mul
>     mul
>     ....
>     mul          * 100th instruction
>     bra       toploop
>
> And again, use the same measuring device to measure the current draw for 1 second.
>
> With a low and high mark, I could then begin measuring other instructions and see where they fall with the high-low current range.
>
> My concern is the accuracy of the measurement, since I expect that the difference in current draw between instructions is small.  This is just a guess, but the level of accuracy that I would need to measure the difference in current draw between instructions would have to be AT LEAST 10e-3, or .001 amp (1 milliamp).
>
> Suggestions?  How would you guys do this? Do I really need the high dollar equipment that I have access to, or do I need a high accuracy, sensitive multimeter that can measure current in very very small amounts?
>
> Any input from the hardware experts here would be much appreciated.
> --
> Boisy G. Pitre
> http://www.tee-boy.com/
>
>
>
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