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HP 50g & SD Cards: Performance, Format, Notes
07-22-2016, 02:32 AM
Post: #31
RE: HP 50g & SD Cards: Performance, Format, Notes
(07-22-2016 12:06 AM)JDW Wrote:  Joe subsequently replied it takes "less than a second" (900ms?) to turn ON with all cards but FAT32. Let's ignore FAT32 and focus on all those other FAT16 cards that take 900ms for the Calc to turn on. I would assume that more than one of those cards has >2MB/s speed ratings. If so, how then does one explain the speed differences Joe posted?

That is my main area of interest. I fully realize the calc is limited to 2MB/s. But if we assume that more than one of Joe's cards has a 10MB/s or even greater rating, how then do we explain the speed differences in Joe's test?

Simple explanation: because of marketing.
When they say 10 MB/s you don't know if it's peak read performance, sustained read performance, sustained write or peak write. Only good manufacturers give you both numbers, and often they cheat too. The PNY card is a class 4, SD Speed class 4 guarantees minimum sustained write speed of 4MB/s (for camcorders), it probably reads around 15 to 20 MB/s. I'd say that's the fastest card in the group.

Joe's test is a write test, so it may not match what you see on the sticker.
If you look at Egan's results, you can see a Lexar card (I think that's a good brand) that reads at 2.5MB/s but writes <300Kb/s. I'm sure they wouldn't put the write speed on the sticker. Sandisk cards are more balanced, so I'd go for their brand first.
I've seen cards rated for 10 MB/s sustained write, but they can only sustain it for 3 or 4 seconds, after that they gradually slow down to 4 MB/s. If you use it on a digital camera, you get 10 MB/s on every picture you take, but if you use it on a camcorder, no joy (learned the hard way). Looking for the SD Speed class symbol is probably your best bet.

On another subject, 900 ms boot is a lot if you use the calc often. I have mine with about half a second, and sometimes I think it's too slow. It has a 64 MB Kingston card.
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RE: HP 50g & SD Cards: Performance, Format, Notes - Claudio L. - 07-22-2016 02:32 AM

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