Thanks Charles, this is all good news.
My current plan is to see how well I can get this working in a non-Linux 
environment
that is relatively small (in terms of flash size) 4Mbyte of NOR with 3 
of the 4Mg
allocated to YAFFS2. Is that reasonable?
> 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
>