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RE: [10GBASE-T] Power Down mode

Title: Power Down mode
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.
 -----Original Message-----
From: Fakterman, Boris []
Sent: Wednesday, August 06, 2003 7:54 AM
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.


Boris Fakterman - Intel Communications Group, Israel

Tel: 972-4-865-6470, Fax: 972-4-865-5999