OESF Portables Forum
General Forums => General Discussion => Topic started by: suruaZ on October 06, 2004, 12:37:13 am
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Hi All,
Just want to ask - do SanDisk Ultra II SD cards work on Z?
If yes - is there any visible speed advantages?
Thanks in advance,
suruaZ
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Hi
If you have a typo and have in mind SanDisk then I had that type of card, wich reminds me to corekt my signature. I returned it because Z didn't want to use all 256 MB. But I'm with 5600 and 1.32 ROM which is more close to Sharp ROM 3.1 for your Z so it might work fine for you. With my new noname MMC card I can't see downgrade in speed. Somebody told me, I think it was tumnus or Greg2, that there is no pint of buying high speed SD or MMC cards because of some hardware isue but I'dont remember what was it. Becide this I think there have been some kind of problem with SanDisk cards which was solved with ne version of kernel module. Plus that you can't use all space on sd card because of security isues. I think that there was something wike 1000b user useble of 1024b or something like that. So my advise is to buy MMC card or even bether CF.
Cheers
Yasen
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[corrected spelling to avoid confusion]
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I just wonder why big read/write speed difference in all those card (MMC, SanDisk, SanDisk Ultra II) is leveled on Z?
suruaZ
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Sharp never implemented support for the faster SD spec. And 'standards' such as Ultra II and SDIO are relatively new so they are not supported either. I think there's also debate about whether the physical SD slot on the Zaurus has all the lines needed to support these extra features.
So basically, all MMC and SD cards are treated as MMC cards. Any variation is speed between cards tends to be small and is probably due to the quality of the cards.
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Becide this I think there have been some kind of problem with SanDisk cards which was solved with ne version of kernel module. Plus that you can't use all space on sd card because of security isues. I think that there was something wike 1000b user useble of 1024b or something like that.
I gave a SanDisk 1GB SD. Normal type. Works fine in my 5600 with Sharp 1.0 ROM.
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I just wonder why big read/write speed difference in all those card (MMC, SanDisk, SanDisk Ultra II) is leveled on Z?
The key is that MMC and SD (in MMC compatibility mode) use a serial interface (data is moved one bit at a time) to get data to and from the card. Contrast that to CF where data is moved one (or two) bytes at a time and you can see that MMC/SD cards are at a significant speed disadvantage. To combat that, the SD spec also defines a "4 bit at a time" mode and faster serial data rates that are not backwards compatible with MMC cards. Special hardware is required to support those features and that hardware is definitely not present in the SL-5000/5500 Zaurii. I don't know about the SL-CXXX series but I'm guessing they're no better off.
Since SD cards in the Zaurus are essentially operating in MMC compatibility mode, the single data path and limited serial data rate pretty much level the playing field. The only area where you may notice significant differences is write speed since that's many times slower than the actual data rate and is driven by the type of flash memory and the programming algorithms in the cards themselves.