Hi,
On Wednesday, March 08, 2017 06:11 AM, Neal Pisenti via ARTIQ wrote:
* For ARTIQ core device, we would ideally jump straight to using a
Kasli, but as that isn't likely to be done in the next few months, I was
planning to use a KC705 as the core.
The "EEM" DDS/synth Kasli extensions may not necessarily be ready before
Kasli. So I don't see how the KC705 helps - is it because you want more
extensions that one Kasli would support? Supporting this KC705 scheme is
more gateware development and one more configuration that needs to be
documented, packaged and maintained. Maintainance means that we need to
check regularly (preferably automatically) that it keeps working when we
modify ARTIQ and fix any bugs that pop up. It takes work.
* KC705 has 2x FMC headers, which would drive 1x VHDCI carrier card,
providing 8x IDC for EEMs. We would buy FMC -> VHDCI adapters for this
interconnect.
What adapters in particular? http://www.ohwr.org/projects/fmc-vhdci? We
didn't check compatibility of any of those.
**Specific questions**:
* what limitations are there (latency/bandwidth/etc) on daisy-chaining
additional Kasili DRTIO modules off of the single KC705 SFP?
While the hardware could do it, daisy-chaining Kaslis is not supported
by the current gateware plans. The plan is to use a Metlino, which has
many available transceiver links (mostly to the microTCA backplane, but
there are also 3 SFPs), as a central device with a direct link to every
satellite device. If daisy-chains are implemented, there would
be virtually no impact on bandwidth, and the latency would increase by
roughly ~100-200ns per hop.
Instead of the daisy chain, it is also possible to have one Kasli as
central device driving directly other Kaslis with its SFPs (note that
one SFP will be used for Ethernet). There are no current gateware plans
for this either (so this would need funding), but it is less difficult
to develop and has less latency.
* Is there an estimate on the timescale for finished Kasli?
It is not funded yet, but I think this should happen in a few months.
Then there will be another few months before it begins to become usable.
Sébastien
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