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General Discussion / sl5600 - SD flash keeps going read-only
« on: March 17, 2004, 03:49:09 pm »
Hi folks
Zbones has just contacted me regarding your favourite gismo and SD cards, and I thought I\'ll try to answer what *could* be going wrong.
First things first, there are two issues with SD cards: corrupted data and slow write times.
Corrupted data
My guess is that your read-only problem is being caused by an issue like the one that affected Dell Axim X5 users; except in the Zaurus\'s case the card goes read only. As you probably know, SD cards have a form of File Allocation Table, to determine when an area of the card is populated with data. What you probably don\'t know is that there is an extension to this FAT to handle data security (i.e. the \"Secure\" part of SD cards...) Now, our \"friends\" at Sandisk, the well known memory card manufacturers created a series of SD cards branded by themselves and others (including Lexar) with a (shall we say) sub-standard controller on the SD card. This controller caused buffer over-flow errors during a write operation causing corruption to the secure part of the SD card. This can lock the card VIA SOFTWARE to a secured-state, i.e. read only! (Sandisk branded cards have a code on the back in the format NNYYMMnN where NN are characters, n is the series code, YYMM are year & month of manufacture...) Note that Sandisk have revised their cards a number of times during 2003 & 2004...
Slow write speeds
SD cards are just like other memory cards (i.e. CF, MMC, MS, xD, SM, etc) where they emulate an ATA hard drive. Unfortunately, some memory card controllers in devices (like PDAs) are not too compatable with certain brands of SD cards, and what they do is drop the i/o speed to mantain reliable access with the SD card. For example, I own over 600 SD cards. I actually only use 2 - a 256mb SimpleTech and a 512mb Panasonic. The SimpleTech, based on a Hitachi SD memory chip, is 300% faster writing than the Panasonic in my PDA (a Ipaq 2210) but the same speed in my camera (Minolta Dimage Xt). I guess you folks need to identify what cards are faster by timing a large file write to your SD cards and then posting the results...
Hope this helps.
Zbones has just contacted me regarding your favourite gismo and SD cards, and I thought I\'ll try to answer what *could* be going wrong.
First things first, there are two issues with SD cards: corrupted data and slow write times.
Corrupted data
My guess is that your read-only problem is being caused by an issue like the one that affected Dell Axim X5 users; except in the Zaurus\'s case the card goes read only. As you probably know, SD cards have a form of File Allocation Table, to determine when an area of the card is populated with data. What you probably don\'t know is that there is an extension to this FAT to handle data security (i.e. the \"Secure\" part of SD cards...) Now, our \"friends\" at Sandisk, the well known memory card manufacturers created a series of SD cards branded by themselves and others (including Lexar) with a (shall we say) sub-standard controller on the SD card. This controller caused buffer over-flow errors during a write operation causing corruption to the secure part of the SD card. This can lock the card VIA SOFTWARE to a secured-state, i.e. read only! (Sandisk branded cards have a code on the back in the format NNYYMMnN where NN are characters, n is the series code, YYMM are year & month of manufacture...) Note that Sandisk have revised their cards a number of times during 2003 & 2004...
Slow write speeds
SD cards are just like other memory cards (i.e. CF, MMC, MS, xD, SM, etc) where they emulate an ATA hard drive. Unfortunately, some memory card controllers in devices (like PDAs) are not too compatable with certain brands of SD cards, and what they do is drop the i/o speed to mantain reliable access with the SD card. For example, I own over 600 SD cards. I actually only use 2 - a 256mb SimpleTech and a 512mb Panasonic. The SimpleTech, based on a Hitachi SD memory chip, is 300% faster writing than the Panasonic in my PDA (a Ipaq 2210) but the same speed in my camera (Minolta Dimage Xt). I guess you folks need to identify what cards are faster by timing a large file write to your SD cards and then posting the results...
Hope this helps.