RE: [10GBASE-T] Power Down mode
Title: Power Down mode
Boris,
I don't think one
can extrapolate from laptop/desktop traffic patterns to data centers.
The
concern for power levels includes:
ability to dissipate the heat generated, ability to supply the power
and reliability effect of higher temperatures due to power. The first
factor depends on the power level averaged over minutes/hours rather than days
or weeks. The second factor depends on average power over sub-second times -
whatever the decoupling capacitors can smooth out.
There will be times
when utilization is high for an extended period. Such times can be hours (think
about big disk back-ups for instance).
A power down mode is
mainly helpful in response to total energy use concerns (saving the batteries or
the planet) for systems that are sporatically active. It might be useful for
reliability concerns (reducing total time spent at high
temperatures). It doesn't answer concerns about power handling
capability.
Also, from data
center customers we often get concerns about latency including latency when an
active period begins. I expect that transitioning from a low power mode to full
operation would take non-zero time. There are already concerns about other
delays (e.g. TCP congestion window) when moving from inactive to
active. I expect that there would be some delay for adaptation when starting
up.
Given all the above,
I don't think a power down mode is useful in answering technical feasibility
issues of power consumption. There may be other reasons to consider it in the
project, though it seems it would be a long time before people were deploying 10
Gig in battery powered devices.
Pat
-----Original Message-----
From:
Fakterman, Boris [mailto:boris.fakterman@intel.com]
Sent: Wednesday,
August 06, 2003 7:54 AM
To:
stds-802-3-10gbt@ieee.org
Subject: [10GBASE-T] Power Down
mode
Hello all,
Following the discussion regarding power, it looks like there is a
consensus that the 10Gb Phy dissipated power will be very high at first
silicon and relatively high at advanced future versions.
The average power is important for most problematic topics,
such as thermal conditions, power source availability and so
on.
The average power can be
reduced by using the Power-Down mode. The transceiver does not transmit or
receive data during significant periods of time. Instead of transmitting idle
symbols while consuming full power, the system can enter the Power-Down mode.
The transmitter power can be reduced by stopping the transmission, the
receiver power can be reduced as only minimal receive functions will be
active. The overall dissipated power during the Power-Done can be reduced
significantly.
Of course there are
algorithmic issues to solve, such as how to maintain the synchronization
during the Power-Down mode, but these are technical problems that can be
discussed and solved.
The average power with implemented Power Down mode depends
on the length of idle periods.
The desktop/laptop PC transmits
idles most of the time ( > 90%
?). I don't know what happens in data
centers.
.If we can reduce even half of the dissipated power by the Power Down mode, it is worth to be considered.
Regards,
Boris
Fakterman - Intel Communications Group, Israel
Tel: 972-4-865-6470, Fax: 972-4-865-5999
mailto:boris.fakterman@intel.com