HARI Systems Design
Hello all and Happy Holidays.
I am very perplexed about a few issues that really bother me. First,
and for most, the comment: "Don't you think that this is either a
little early, or does someone have a hidden agenda?" from Roy's email
this morning in one of the many HARI threads. Unless I am mistaken, I
have not viewed this, nor any proposal by anyone as a hidden agenda. If
you did call HARI a hidden agenda, then you could call two phys a hidden
agenda, SONET a hidden agenda, etc, etc. Correct me if I am wrong,
people, but I thought all the presentations were from people who believe
they have a good idea to offer to the standard, might benifit them a
little, but still a good presentation - or have I just stayed on the
farm a little too long?
In terms of systems design, "As for real estate on the PC board.
Vendors need to think about reducing the size
of their boards and systems. More and more floor space is being taken
by these systems as well as power and cooling. Reducing the size of the
boards, reducing the amount of electronics, reducing power requirements,
and increasing the density of the connections is becoming an issue in
large installations, like those that will use P802.3ae. Hari tends to
take exactly the opposite direction in system design. Hari makes it
easy for the system designer to become sloppy, not requiring them to
become tighter and better." I think I would like to take this line by
line.
Vendors need to think about reducing the size of their boards and
systems : Well, how about customers should require less features. Then
I wouldn't have to go to extraordinary means to get all the components
shoved into a small bucket. If you want less power, less space, less
connections, then drop some features.
Board Size: We fit more onto boards today on a gate per sq in level
then we ever have at a lower price. We are beginning to abandon fr-4
for newer materials at less cost per route length and more routing
density.
Thermal and power: Reducing voltages to 2.5v and 3.3v have helped.
Power bricks are getting much more efficient. Using CMOS over GaAs and
Bipolar have helped. We are all required to meet Telcordia
requirements, so there is only so much heat per sq foot we are allowed
to produce. Space and thermal and weight ARE already a standard.
Hari makes it easy for the system designer to become sloppy, not
requiring them to become tighter and better: Wow! Hari or something
similar does no such thing. It allows the designer the ability to
re-partition the problem. But, on the other hand, maybe I should be
against Hari because then that would force most people to think about
10gig serial streams for long distances on copper traces ( which most
companies can not aford to develop ) and go with very wide 622mhz data
paths so my boards get thicker and more expensive - this allows the
designer the greater headache of routing and board fab issues. I don't
know, if sloppy were true, all of us would be out of business. I have
seen most of the systems available today and we all pretty much design
the same, have the same issues, and make the same trade-offs to supply
the customer all the features they require to make the sale.
So, in summary, Hari is a starting place, as I have mentioned before.
Even the GMII and MII, etc have issues. But we have a proposal(s) of a
start .... how about we try to constructively look at what hari solves
or doesn't solve. So how do we design Hari to be 'phy independent'?
Because at the moment, Hari solves most of my SI issues. Oh yeah, the
job description for the SI guy is as follows : Comes up with last minute
desperate solutions to impossible problems caused by the System
Architect.
Joel