About why Intel is vulnerable to Meltdown and AMD, while Intel basically
licensed the x64 instruction set from AMD the actual implementation of
those instructions is completely different.
The instruction set for x86 and x64 is targeted at Complex Instruction
Set Computers (CISCs) however the underlying architecture of the Intel
CPU is a hybrid CISC/RISC design. Intel can issue microcode updates to
alter how x86/x64 instructions are mapped/translated into CISC/RISC
architecture to fix execution issues and some security issues. As
already been discussed widely the Meltdown security failure is core CPU
functionality which has to be programmed around, so that OS Kernel
Memory has to exist in a separate Virtual Machine from the User
Programs. When an application needs to access the kernel it makes the
function call which triggers the OS to save the request before switching
to the kernel Virtual Machine which can then process the request, but
the process is reversed to return the results to the user application.
Which is why Amazon have issued performance warnings, Microsoft Azure
customers are complaining about broken servers.
AMD also has a combined CISC/RISC design but it is completely different
from Intel which is why it is not susceptible to Meltdown and is
susceptible to only one of the Spectre vulnerabilities.
In respect of ARM processors, Apple designs it own ARM processors which
is why all their products are effected by Meltdown but only one of the
standard ARM production cores is known to be susceptible. Equally
Qualcomm designs its own ARM chips which have be reported to vulnerable
In order to address vulnerabilities in speculative instruction execution
the CPU should write the information into a separate L1 cache which
implements process locking to stop other processes from accessing the
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