<wpwrak>
must be an interesting definition of "compatible' :)
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<DocScrutinizer05>
x86 dma been slower than CPU sw mem-move since 80186 iirc
<DocScrutinizer05>
unless CPU does other stuff while DMA completes, it's way more overhead to set up DMA than to do same stuff in software. Even when both in the end reach same transfer rate. And nowadays DMA often is a relic like A20 gate, with CPU copying 10 words in the time where DMA moves one byte
<wpwrak>
well, x86 dma is kinda special :)
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<whitequark>
oh, that spectrophotometer thing again
<whitequark>
it's practically useless
<nicksydney>
why useless ?
<nicksydney>
$2Million dollar is not useless :)
<whitequark>
well, it's useful to the ones producing it, sure
<nicksydney>
time will tell whether they deliver or not..if they do deliver and backers are happy than it's worth the $2Million
<nicksydney>
wpwrak: it's using BLE too :)
<whitequark>
nicksydney: they probably will. it doesn't matter. it's a very expensive toy that you can't really use for anything interesting except "omg an apple"
<larsc>
I don't think you need your smartphone to tell an apple and a banna appart ;)
<larsc>
banana
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<larsc>
apelete: try to find out why and where the DMA based transfers spend there time compared to the PIO method
<larsc>
maybe that will tell you why it takes longer
<larsc>
00:37 < whitequark> wow, pio faster than dma
<larsc>
00:37 < apelete> larsc: it takes twice as long to boot with dma enabled, shouldn't dma be faster than pio ?
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<pcercuei>
apelete: good job!
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<apelete>
pcercuei: thanks :)
<apelete>
larsc: I was thinking about using something like bootchart, but I guess it won't be detailed enough to spot dma transfers
<larsc>
yes
<apelete>
larsc: do you think ftrace could help ?
<pcercuei>
apelete: what CPU usage do you have during transfers? Ingenic's MMC driver for jz4770 uses DMA, is slow, and uses a lot the CPU
<apelete>
pcercuei: don't know yet, I only looked at the boot log timing
<apelete>
I'm going to try a "zcat file >/dev/null" with PIO vs. DMA like wpwrak was suggesting last night
<larsc>
apelete: Use something like getrawmonotonic() in the driver and messure the time it takes to transfer one block
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* DocScrutinizer05
wonders if they really got a proper mass spectrometer in that SCiO thing. If they do (I seen an early prototype of a sugar cube sized mass spectro several years ago at embedded fair in Nuernberg) then this could become a damn lot more than just "tell apat apples from banana" - it would be Abby's wet dream: Major Mass-Spectrometer in your pocket
<whitequark>
DocScrutinizer05: it's NOT a mass spectrometer
<whitequark>
you can't have a mass spectrometer without at least a turbomolecular pump, and even if you have, it's more or less useless without a chromatograph
<whitequark>
they quite plainly explain that what they have is a simple spectrophotometer
<DocScrutinizer05>
the sugar-cube-mass-spectro was a damn smart ting: thanks to micro size they didn't need to evacuate the "chamber" where molecules get "sorted" in an electric field. And also thanks to the tiny size of the thing, really low voltages were sufficient to create the field to accelerate and deviate the molecules
<whitequark>
DocScrutinizer05: your sugar-cube thing is NOT a mass-spectrometer
<DocScrutinizer05>
you may have a few buzzwords, maybe you find a link by yourself: mass spectrometer; fraunhofer; embedded Nuernberg
<DocScrutinizer05>
and a time frame: maybe 6 to 12 years ago
<whitequark>
was the first thing I did
<whitequark>
no relevant results
<whitequark>
link above is the closest one I found
<whitequark>
there's some interesting results from DARPA, but what they have is supposed to work on Mars
<whitequark>
which means you don't even need to have a rough pump. considerably simpler
<DocScrutinizer05>
I talked with the guy and asked him "but how do you evacuate the thing?". He answered "we don't need to, the gap is so small only a few molecules come in anyway, no matter if it's air or the test substance"
<whitequark>
interesting
<whitequark>
did he publish the result in a journal or something?
<DocScrutinizer05>
I asked him "but you need high voltages to accelerate and do the deviating field, no?" he answered: " look at this tiny cube. Now figure we have hundreds of electrodes in there, each powered from normal 5V digital logic. We create fields of kV to MV per meter, thanks to the tiny structures"
<whitequark>
since it's not evacuated, wouldn't such high potential gradient just cause a discharge?
<whitequark>
and even if it would be
<DocScrutinizer05>
the gap is so small, there are only a few "dozen" molecules of anything in there at all
<DocScrutinizer05>
the space is too narrow to contain anything other than a pretty good vacuum
<DocScrutinizer05>
check out the gradients you have in CPU chips
<DocScrutinizer05>
horrid
<DocScrutinizer05>
when you power a modern chip with 5V instead of 1.2V, it probably has sparks all over the complete die ;-)
<DocScrutinizer05>
a trace with high potential and a ground level trace my be separated only a few dozen nanometers
<DocScrutinizer05>
may*
<whitequark>
hm, you're right
<DocScrutinizer05>
1V difference makes for a gradient of 10E6 to 10E8V/m
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