
Intel: Meltdown, Spectre silicon fixes coming 2018; 3D XPoint RAM, not so much - jjuhl
https://arstechnica.com/gadgets/2018/01/intel-meltdown-spectre-silicon-fixes-coming-2018-3d-xpoint-ram-not-so-much/
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hannob
Reading the headline I had wished for more details.

What does it mean to fix spectre? The microcode updates that were presented
weren't... very elaborate as far as I understood it. They basically add
optional capabilities for software to say "please let speculative execution
run into nowhere and I know it'll be really slow".

What will these fixes look like? Will they add memory permission management to
speculative execution? Is that even possible? Will they move away from
speculative execution? Is it possible to have a performant processor without
it? Will the fixes "just work" or will they require changes in software? In
compilers? Will they be on by default or only for sensitive processes?

~~~
Tuna-Fish
> Will they add memory permission management to speculative execution?

Probably.

> Is that even possible?

That's how AMD does it, so yes. Simply refusing to return a result from memory
before the permissions are checked is a good solution to Meltdown. Might be a
little slower in some situations, but it shouldn't be terrible.

> Will they move away from speculative execution? Is it possible to have a
> performant processor without it?

No and no.

Spectre 2 can be fixed by storing more bits in BTB tags, including the PCID
and possibly some id to distinguish between VMs. If they don't want to do
that, they can fix the issue with somewhat more of a performance penalty by
introducing a fast operation to clear the BTB, which would be used when
switching between privilege levels.

> Will the fixes "just work" or will they require changes in software? In
> compilers?

Spectre 1 cannot be fixed, and the only solution is to accept that branches
cannot be used as security boundaries.

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nirv
So Intel just hit earnings records[1] for 2017Q4 despite all the vulns (AMT).
And now, after recent events (Meltdown/Spectre) with no warranty losses, are
anticipated in excitement to hit new records in 2018Q4 with new, apparently
not much faster, but fixed CPUs. Awesome.

[1] [https://www.anandtech.com/show/12371/intel-
announces-q4-2017...](https://www.anandtech.com/show/12371/intel-
announces-q4-2017-and-fy-2017-results)

~~~
boolish
Intel has absolutely no incentive to do anything about any of these problems.
They are the definition of a monopoly.

~~~
ams6110
Intel does not have a monopoly. The do have the best (i.e. fastest) processors
for some applications. But having the best product in a market niche is not a
monopoly.

AMD make instruction-compatible CPUs and other vendors make other computing
architures (POWER, ARM, SPARC, etc.) that all compete with Intel.

~~~
tpurves
Regardless of comparative product quality, AMD does not have access to the fab
capacity to compete with more than 10-20% of the volume of CPUs that intel
ships. AMD is the only other x86 competitor which, for the time being, are not
easily replaceable for a large swath of the market (eg desktop and server
cpus). AMD can threaten Intel’s margins, or up to 20% of their volume, but
otherwise intel is monopolistic to a significant degree.

~~~
petra
Is that capacity only from global foundries ? What about tsmc ?

~~~
Tuna-Fish
As of right now, AMD only designs their CPUs to work on the GloFo foundry.
They could relatively easily expand production to the samsung fabs (as those
are using almost the same process), but moving to use TSMC would require
expensive and time-consuming redesign.

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kartD
Highly doubt that any proper silicon fix is going to be out this year. Silicon
validation is no joke, so I’d expect 3years before speculation issues are
fixed properly. I think the new fixes will be in microcode instead

~~~
0xFFC
Sorry for asking, what is Silicon Validation? and how it is related to
Meltdown, Spectre?

~~~
ohazi
Simulating and testing the design. You generally don't want to spend millions
of dollars on a semiconductor mask set unless you're sure the design will work
correctly.

This part usually takes longer than the actual logic design and transistor
layout phases.

~~~
robin_reala
> You generally don't want to spend millions of dollars on a semiconductor
> mask set unless you're sure the design will work correctly.

For varying levels of sure, given recent history.

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Animats
OK, time to hold off on computer purchases until the fixed version is out the
door. Maybe by then the big GPU shortage due to cryptocurrency mining will
have been resolved.

