It depends on the complexity of the fixes. We're probably not talking additional instructions here, only some smaller microarchitectural changes (at least for Meltdown), which could conceivably take only 6-9 months to put into production after design.

I wouldn't expect anything before Q3, but Q3 or Q4 shipping does seem plausible.

The worst case is when they manage to fix Spectre/Meltdown but then introduce a bunch of other errata in the process because they rushed it. The errata lists for modern processors are already disturbingly long, and this is for things that aren't "merely" timing side-channels but actual "not as designed" defects.

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

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.

> 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.

I don't know the semi-conductor specifics... but it's a broad engineering concept.

Validation: Does the thing you designed actually do what it's supposed to do?

And the related concept,

Verification: Is the thing you build (and deliver) actually what you designed?