I currently have a 2014 MacBook Pro, but it needs to go in for service and, rather than renting one for a week, I was thinking of buying a cheap backup (maybe from 2011 or 2012). What is the oldest model that would incorporate Intel's complete set of patches for Meltdown/Spectre (aka Speculative Store Bypass Variants 1–3)?
According to what I've read (see details and sources, below), patches are available from Intel for the chips used in the 2010 and later 15"/17" MBP's, and for the 2011 and later 13" MBPs.
[DETAILS AND SOURCES: According to Intel's patch guidance (https://newsroom.intel.com/wp-content/uploads/sites/11/2018/04/microcode-update-guidance.pdf), patches have been offered for Sandy Bridge and Arrandale, but not for Penryn. And according to https://en.wikipedia.org/wiki/MacBook_Pro (go to "Table of second generation MacBook Pro models" and click "Show"), the 2011's all use Sandy Bridge. With the 2010's, it gets a bit tricky: The 2010 MBP's used either 2.4 GHz (P8600) or 2.66 GHz (P8800) Penryn chips; or 2.4 GHz (520M), 2.53 GHz (540M), or 2.66 GHz (620M) Arrandale chips. And, according to https://everymac.com/systems/apple/macbook_pro/macbook-pro-unibody-faq/differences-between-macbook-pro-13-15-17-inch-early-2011-and-mid-2010.html, the Penryns are in the 13", while the Arrandles are in the 15"/17"; if that's correct, patches are available for the chips used in the 2010 15"/17" models, but not the 2010 13" ones. The models from 2009 and earlier all use Penryn or earlier, so none of these are patched.]
However, it's not sufficient that Intel offers the patches. It also needs to be the case that Apple has incorporated those patches into the latest OS the chip family is capable of running. According to this chart (https://www.apple.com/lae/macos/how-to-upgrade/#hardware-requirements), one can run High Sierra on all MBP's from 2010 onward. But that doesn't necessarily mean that Apple, within High Sierra, has made available patches going as far back as possible (i.e., that High Sierra contains Intel's Sandy Bridge & Arrandale patches). I assume it has, but I'd like confirmation.
Further, there's a practical performance question: I've not noticed a performance difference with the patch on my mid-2014 MBP. But is the percentage degradation in performance significantly higher with older chips? ["We may see a marginal impact and take a bit of a hit, but the newer processors don't have a huge loss. Older processors have more of an impact." ——John Michener, Chief Scientist, Casaba Security. Source: https://www.wired.com/story/meltdown-and-spectre-patches-take-toll/ ] [I don't know if he means that older processors show more percentage degradation, or simply that older processors, being slower to start with, have less performance headroom.]
Pragmatically, I'd like it to be decently-usable (rather than marginally usable) with Office 365 (even my top-of-the-line 2.8 GHz mid-2014 15" model struggles a bit with Office).