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Finding a CPU design bug in the Xbox 360
By Thom Holwerda on 2018-01-08 13:29:28

The recent reveal of Meltdown and Spectre reminded me of the time I found a related design bug in the Xbox 360 CPU - a newly added instruction whose mere existence was dangerous.

Back in 2005 I was the Xbox 360 CPU guy. I lived and breathed that chip. I still have a 30-cm CPU wafer on my wall, and a four-foot poster of the CPU’s layout. I spent so much time understanding how that CPU's pipelines worked that when I was asked to investigate some impossible crashes I was able to intuit how a design bug must be their cause. But first, some background...

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We have agents, actually, within the silicon.
By dionicio on 2018-01-09 15:02:57
"But it’s okay, because it’s “just a prediction” and it doesn’t need to be right."

To predict is a form of "operative" language. And as such, implies the creation of a comm link. System designers Should always consider this.

In the human sphere CAUSES branching, both at asking and asked agents, both before and after, comm event.

We have agents, actually, within the silicon.

"Exploratory" Talks have a reason. Actually DELIMITS the Universe of Negotiation.

Concluding, Could it be the case, that some predictive works, actually derail discourse, and in doing that, TIME, which could actually impede Solution Reaching.

Edited 2018-01-09 15:22 UTC
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Comment by dionicio
By dionicio on 2018-01-09 16:04:41
I should know by now,
what he has ACTUALLY speculated by now,
about what she had predicted just before
about my next action.

BEFORE actually taking that NEXT action.

:) Purpose of prediction then?

Are He and She MY agents, to begin with?

Edited 2018-01-09 16:09 UTC
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Comment by dionicio
By dionicio on 2018-01-09 16:32:20
At The Cell processor case. She has brought 4 addresses to the pipeline. One processor architecturally able to speculate on them. Fortunately that one is busy on the main execution.

Any speculation is triggered by the actual code, which could be, an emulator of another processor. Alas, becoming susceptible to the bug, through an ad-hoc implementation.
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In The Age Of Single Digit Micron Architectures
By dionicio on 2018-01-09 17:31:51
Every branch has to have Total 'universe' independence; temporal and spacial. You will not be able to brag about coherency until Physically addressing that:

An idea could Be To Handle parallel branching execution through transputers, and To Handle non-branching code through whatever better fits.

In The Age Of Single Digit Micron Architectures, That's not so far fetched.

That WONT require any change on Huge Legacies and Mind dominions. And Will bring new frontiers to those wishing to program directly to the transputers, through a brand new set of commands.

Edited 2018-01-09 17:41 UTC
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