[Haskell-cafe] CPU with Haskell support

[Joachim Durchholz]

Am 20.01.2016 um 18:09 schrieb Maurizio Vitale:
> As for modifying the instruction set of an Intel processor, I don't know
> how feasible it is.

Some CPUs allowed this. There were even designs that had PL/1 
instructions implemented as assembly by way of microcode.

In theory it's possible for newer Intel CPUs.
One point against doing so is that the microcode updates are 2-8 kBytes 
in size. You'd need to switch microcode with every context switch in the 
operating system.
The other point is that microcode updates are encrypted and signed. Only 
Intel has the private keys needed to provide data so that an Intel CPU 
will accept a microcode update (this is supposed to prevent tampering 
with the microcode update data by malicious third parties).

Sources:
http://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-vol-3a-part-1-manual.pdf#zoom=100 
pp. 338 ff. has infos about the general format of an update.
http://www.delidded.com/how-to-update-cpu-microcode-in-award-or-phoenix-bios/ 
lists typical microcode update sizes near the end (not sure whether 
these are in bytes or in DWORDs).

Regards,
Jo