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