Advanced Micro Devices Inc (AMD)

[chipguy]

I was not talking about *instantaneous* power draw. I was talking about power draw over a period of time

Sorry but you said "instantaneous power" so I thought you meant instaneous power. I should
have first consulted my spokeshave prevarication magic decoder ring to establish that you
were really taking about energy before responding to yout post.


At any rate, this is not what decoupling capacitors are for. It may well be
an ancillary function to fill in the power gaps created by transients, but the
primary function of decaps is to isolate the device from the power bus noise.

Wrong. The purpose of decoupling caps to shield the device being powered from
the effect of the power supply inductance which would otherwise cause wild transient
in local voltage in response to large di/dt events in the device iteself. The noise that
would otherwise cause failure is locally generated, not brought in from the power bus.

Here's a reference that may be suitable for your apparent level of understanding of high
speed microelectronics. It even has a description of typical uP current transient:

http://www.paktron.com/techarticles/hi_speed_circuit/high_speed.html

"The inductance of a system (caused by cables, power planes, etc.) slows a power supply's
ability to respond to these rapidly changing current requirements. Both bulk and high frequency
bypass capacitors are required because of the relatively slow speed at which a power supply
(or a DC-to-DC converter) can react. For example, a microprocessor's current transients are on
the order of 1-20 ns while a typical voltage converter has a reaction time of 1-100 µs. Properly
selected bulk capacitors will slow the transient requirement seen by the power source to a rate
that the power source can supply by furnishing energy to the system until the power source can
react to the demand."

Hmmm, 1 to 20 ns. No mention of shielding the uP from power bus noise either. Whatever
could this mean?, LOL.

Quite a few critics of Intel's TDP numbers like to ignore them and multiply Icc_max and Vcc_max

You have found a second flaw in this approach (ie. the load line) and I thank you for providing
me even more ammunition to debunk this myth.

So, then, it is your contention that the loadline is flawed and is a myth?

From this comment I can only presume you are deliberately being obtuse.