[Libre-soc-bugs] [Bug 855] add libre-soc to kestrel

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=855

--- Comment #33 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
(In reply to tpearson from comment #32)
> Things are currently a bit unstable at 60MHz, but a quick check at 50MHz is
> showing better functionality.  Over time, as part of a different project,
> we'll be working on getting the timing fixed -- for now, 50MHz is the
> known-good target for at least the industrial grade Arctic Tern modules
> (commercial grade may be able to go faster).

manufacturing tolerances on DRAM ICs is rather unfortunately in the range
48 to 55 mhz.  the *listed* minimum clock rate in datasheets is 100 mhz!
i.e. if you can get stability at 55 mhz then chances are high all product
sold will work.

unnfortunately i learned recently that nextpnr is not capable of dealing
with twin non-synchronous clocks. i.e. it will screw up the routing if
you try CDC.

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