mattybain;171598 Wrote: > I am curious whether anybody has had any success with the 4gb SD cards > that are around. I know Nokia says 2gb is the limit but with most of > their devices the limit is usually bendable.
I'm currently using two Transcend 4GB SD cards (TS4GSD150) successfully in the N800, for a total of slightly under 8GB removable storage. But there are a few gotchas: Make sure you buy regular SD cards, not SDHC "high capacity" which do *NOT* work at this time. 4GB cards exist in both flavors, so the difference is crucial. 8GB and future higher capacities (up to 32GB under the spec) will always be SDHC as well. Linux kernel support for SDHC has recently become available, so there is good reason to expect it will be ported to the N800 in the foreseeable future. (With the original Nokia 770, 2GB RS-MMC support arrived via a similar midlife upgrade.) If your need for maxed-out storage is not immediate, you might want to monitor www.internettablettalk.com for new developments on this front. Also, it's doubtful whether "high speed" or "ultra speed" cards (like the 150X models noted above) will perform any better than "normal speed" (e.g., Transcend TS4GSDC) in this device. Crude benchmarks suggest that the N800 clocks its SD slots at 25MHz, not the 50MHz required for higher transfer rates. Given this constraint and the expected addition of SDHC support in the near future, normal speed cards might be the smarter choice today. Finally, if your intended usage involves large numbers of very small files (such as maps for GPS navigation), I _strongly_ recommend reformatting the SD card with smaller clusters. This can be done over the USB connection to a Windows PC, as well as Linux console tools. My cards came preformatted as FAT32 with 32KB clusters, which is extremely inefficient for this particular application. For a concrete example, the open source Maemo Mapper works with downloaded maps from various sources, including Google Maps. It stitches the display from 256x256 pixel tiles in PNG format (streets) or JPG (topo). At the largest scale (zoom level 15), a 4x4 grid (16 tiles) covers the globe. Each successive level zooms in by a factor of 2, needing 4 times as many tiles to cover a given area. The most detailed PNG tiles take roughly 50KB each, but the average is much lower, with a lower bound of 103 bytes for featureless areas such as open water. Most users amass a collection of large scale maps for large areas, amplified by smaller scales for specific areas or individual routes. Full global coverage at zoom levels 10 - 15 comprises 21,840 files, totaling 32.2MB at this time (subject to change as the database evolves). With the default 32KB FAT32 clusters, these files occupy 684MB on the 4GB flash card: over 95% wasted space! Reformatting with 1KB FAT32 clusters slashed the allocation to 48.5MB, or a 14X improvement in storage density. A 2GB SD card could do even better with 512 byte clusters (the FAT32 minimum), but this option is unavailable for 4GB and larger partitions. The downside to reformatting is reduced throughput, since the allocation units become smaller than the internal block size of the flash device. So cards intended for larger files such as audio, video or photos should be left at the factory format. -- jpj ------------------------------------------------------------------------ jpj's Profile: http://forums.slimdevices.com/member.php?userid=1564 View this thread: http://forums.slimdevices.com/showthread.php?t=31398 _______________________________________________ discuss mailing list discuss@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/discuss
