[Libre-soc-dev] NGI POINTER gigabit ethernet router ASIC roadmap
luke.leighton at gmail.com
Wed Nov 3 14:51:09 GMT 2021
On Tue, Nov 2, 2021 at 2:16 PM lkcl <luke.leighton at gmail.com> wrote:
> On Mon, Nov 1, 2021 at 11:11 AM lkcl <luke.leighton at gmail.com> wrote:
> > * there is not enough time to do out-of-order (it was 5 months just
> > doing the 6600 experiment), a FSM is too slow therefore we do an
> > in-order core making sure to plan ahead for OoO (use ReservationStations,
> > use MultiCompUnits)
> deep breath: i tested the use of the ReservationStations class
> (developed over 2 years ago), and it is the first time it is "hit"
> by full-on ready/valid Signalling: it didn't work.
it didn't work because of an oversight in the design.
* Reservation Stations need to be latched as actually reserved
until such time as the same MUX id is seen at the output
(final stage of the single pipeline).
* this means raising a "busy" flag - *per input* (per RS)
indefinitely until such time as the MUX id pops out the
* the first design relied on state information known by the
*sender* to respect the MUX ids.
* thus, what i had written is more of a multi-in multi-out arbitrator / routing
system, not a ReservationStation, at all.
this will need a redesign.
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