On Thursday 13 September 2012 05:10:13 Ed Sutter wrote:
> Hi,
> Our use of YAFFS2 will initially be on a NOR-based system, not running
> Linux.
> I've read (on this list and on the yaffs site) that YAFFS2 works with NOR
> flash as well as NAND. Since NOR is quite different than NAND, I'd be
> interested to know how common YAFFS-on-NOR is and what the pitfalls are
> (if any).
An extremely robust solution is indeed very possible and has been used by
quite a few organisations to ship high and low volume products.
>
> For example, I did read somewhere that it is substantially slower to
> write files,
> so it would be nice to know how much slower.
NOR is far slower to write and erase than NAND. That creates a bottleneck to
write speed.
Write speed will depend very much on how much grabage collection (and thus
erasure) is being performed. Yaffs only adds a small overhead to this.
No hard numbers are possible because everything is so hardware dependent. You
can get a ballpark number by timing some raw NOR writes and adding, say, a
10% overhead.
> Also, are things like
> wear-leveling,
> garbage-collection and power-hit safety tested in a NOR based environment?
Most certainly.
Wear levelling is achieved by the way yaffs allocates blocks to achieve a log
structure.
Power fail handling is part of the test suites that run on average for a few
hours every week. Power failures are simulated at a bit level on NOR.
-- CHarles
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