Re: 16-bit 625Mbaud XGMII
Booth,
I do not mind specifying a 4-lane additional optional
interface for Copper as long as the electrical specs of
this interface are included as part of the specific
standardized optical PMDs. In other words, there will not be
an universal 4-lane electrical specification over Copper
that all the various optical PMD proposals have to obey to.
Specifically:
1) the 64/66 proponents may define an optional
4-lane Copper interface at 2.578 Gbaud that fits
perfectly with the type of coding they want on the
optical fiber.
2) the 8b/10b proponents may define an optional
4-lane Copper interface at 3.125 Gbaud that fits
perfectly with the type of coding they want on the
optical fiber.
3) the PAM-5 proponents may define an optional
4-lane Copper interface at 1.25 Gbaud that fits
perfectly with the type of coding they want on the
optical fiber.
And so on. Compatibility and interoperability at this
4-lane Copper interface would not be required, since
the coding schemes are different.
Only in this context I would support the additional 4-lane
optional Copper interface. These optical-PMD-specific
Copper interfaces would be very valuable. In particular,
I plan to implement an exposed 4-lane interface using
option # 3 and I consider it very useful to specify
the electrical characteristics of this interface in
the standard, so multiple vendors can use PAM-5 coding
on the fiber and be compatible and interoperable
at the 4-lane PAM-5 Copper interface.
Now, if you just want to transport 10 Gbps data
on a Copper backplane and nothing else (LOM, LAN On
Motherborad) - then you are free to use the coding scheme
you like, including the one proposed by Infiniband. But this
type of application is being dealt with in other forums, not in
the 802.3ae.
Jaime
Jaime E. Kardontchik
Micro Linear
San Jose, CA 95131
email: kardontchik.jaime@xxxxxxxxxxx
"Booth, Bradley" wrote:
> Jaime,
>
> I have to disagree with your point below that XGMII should be the only
> specified interface. I think that it would be extremely short-sighted of
> the P802.3ae Task Force to develop one standardize interface that seriously
> impedes and may even prevent certain implementations. XGMII provides a
> format for information flowing to and from the Reconciliation Sublayer and
> PCS, but XGMII is seriously limited in the distance it can transmit over
> FR-4 PCB traces. XAUI provides a method for increasing the distance and
> lowering the pin count; both of which are extremely desirable in
> switch/router implementations and LOM (LAN-on-Motherboard) implementations.
>
> Thanks,
> Brad
>
> -----Original Message-----
> From: Jaime Kardontchik [SMTP:kardontchik.jaime@xxxxxxxxxxx]
> Sent: Monday, March 20, 2000 5:33 PM
> To: Curt Berg
> Cc: stds-802-3-hssg@xxxxxxxx
> Subject: Re: 16-bit 625Mbaud XGMII
>
> <Other text deleted.>
>
> The only specified interface should be the XGMII.
>
> Jaime
>
> Jaime E. Kardontchik
> Micro Linear
> San Jose, CA 95131
>
>