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Posts: 2,152 | Thanked: 1,490 times | Joined on Jan 2006 @ Czech Republic
#27
Originally Posted by freeman View Post
This is quite hard to answer. but let me try this, Well even though it's exact use more memory in when booting from flash, but the rootfs stored in the flash is in jffs2 and in order for the data to be usable, it got to be uncompressed first, right, so where is that uncompressed data stored?
Well jffs2 is probably optimized for embedded use so I guess it does not take much ram. Maybe it is even optimized for size, not speed :-)
Originally Posted by freeman View Post
the main reason why the system is slow when booted from flash because, all the application(not data stored on SD/MMC) are pretty much in compressed format. The CPU is already underpower at 300MHz already, and now it have to do compression/decompression on the fly, it's another step for the CPU to handle.
Exactly. Even if default n770 kernel has very poor MMC speed the i/o speed is still slightly faster than internal flash due to jffs2 compression overhead and as a bonus the CPU is free to do something else while reading. With internal flash i/o is slower and cpu usage is 100% while reading/writing which slows the device a lot.

Also when you add high speed mmc modes to n770 linux kernel it is even better. I still don't have n800 so I'm not sure about n800 SD slot speed but in 50MHz SD mode (probably not in stock n800 kernel) it should do ~20MB/s (read speed) in theory.