[MAGEEC] Chip variations: tests, results, and graphs

[Alex J Lennon]

Very interesting James. Do you mind me asking what the flash testing
comprised? e.g. read/write/erase cycles?

Best Regards,

Alex

On 27/07/2014 17:13, James Pallister wrote:
> Hi All,
>
> Some preliminary findings on variations in the ATMEGA328 chips.
>
> I've tested 28 chips. For each chip 9 tests were ran:
>
> flash0
> 	Test the area of flash 0x0800-0x0810
> flash1
> 	Test the area of flash 0x080C-0x081C
> flash2
> 	Test the area of flash 0x08FC-0x090C
> flash3
> 	Test the area of flash 0x0FFC-0x100C
> ram0
> 	Repeatedly access 0x0000 - 0x0020
> ram1
> 	Repeatedly access 0xF007 - 0xF017
> alu
> 	Perform combinations of mul, fmul, inc and dec
> nop
> 	Lots of nops
> branch
> 	Repeatedly branch randomly in low flash
>
>
> Each test was run 8 times, and outliers excluded. All were run in the
> same harness, with the same crystal, resistors, etc.
>
> Results across each test. These show the distributions of the
> measurements taken, where the distribution consists of the 28 chips.
>
>
> From the first graph: there is a significant different, even on a day
> to day basis. I'm not sure what causes this - I'd expect the power to
> be lower at lower temperatures, which we don't see.
>
> For each chip:
>
> Mean power for each chip:
>
>
>
> The average power changes quite a lot, going from < 80mW to > 100mW.
> In almost all cases, the average power was higher on Saturday - not
> sure why this is, the temperature difference was only 3-4 degrees (and
> I'd expect the temperature to go down with lower temperature).
>
> The chips tend to vary as a whole, e.g. rather than the ALU varying
> significantly in one part rather than another. The following graph
> marks the average power for each test, divided by test type (different
> color/marker combinations) per chip. This should allow hopefully allow
> us to do a calibration run first.
>
> Legend for the above graph:
> Blue cross
> 	ram1
> Red star
> 	ram0
> Green plus
> 	alu
> Black plus
> 	flash3
> Green cross
> 	flash2
> Blue star
> 	flash1
> Red plus
> 	flash0
> Black star
> 	nop
>
>
>
> Any thoughts / ideas for more tests are welcome.
>
>
> James
>
>
> _______________________________________________
> mageec mailing list
> mageec at mageec.org
> http://mageec.org/cgi-bin/mailman/listinfo/mageec

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mageec.org/pipermail/mageec/attachments/20140727/5915f63c/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 120718 bytes
Desc: not available
URL: <http://mageec.org/pipermail/mageec/attachments/20140727/5915f63c/attachment-0004.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 176160 bytes
Desc: not available
URL: <http://mageec.org/pipermail/mageec/attachments/20140727/5915f63c/attachment-0005.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 44187 bytes
Desc: not available
URL: <http://mageec.org/pipermail/mageec/attachments/20140727/5915f63c/attachment-0006.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 79329 bytes
Desc: not available
URL: <http://mageec.org/pipermail/mageec/attachments/20140727/5915f63c/attachment-0007.png>