Also, overall just a great explanation of the vulnerabilities.
Eben Upton provides a "Explain it like I'm 5" type rundown of the history of processor development that led to the ability to exploit these processors, and access protected memory.
His conclusion:
Modern processors go to great lengths to preserve the abstraction that they are in-order scalar machines that access memory directly, while in fact using a host of techniques including caching, instruction reordering, and speculation to deliver much higher performance than a simple processor could hope to achieve. Meltdown and Spectre are examples of what happens when we reason about security in the context of that abstraction, and then encounter minor discrepancies between the abstraction and reality.
The lack of speculation in the ARM1176, Cortex-A7, and Cortex-A53 cores used in Raspberry Pi render us immune to attacks of the sort.
The whole article is highly recommended. Probably the best and most straightforward description of the issue I've seen.
