[GTALUG] Skylake bug

Lennart Sorensen lsorense at csclub.uwaterloo.ca
Tue Jan 12 16:41:40 UTC 2016


On Tue, Jan 12, 2016 at 03:06:27PM -0500, James Knott wrote:
> Many years ago, I worked as a computer tech, maintaining various models
> of minicomputer.  One thing some computers had then was accessable
> microcode.  With the Data General Eclipse line, the microcode was stored
> in ROM, but if the Writable Control Store (WCS) option was installed,
> you could add new or even modify existing instructions.  The DEC VAX
> 11/780 loaded it's microcode from a floppy at every boot, so it was a
> simple matter to provide an updated version.
> 
> It was "fun" trouble shooting a problem by stepping through the
> microcode.  ;-)

The alpha couldn't do memory management without extra instructions loaded
at boot (usually by the firmware, although milo could fake it).
Those instructions were written in a special low level instruction
language for the alpha which had access to internal registers for the
MMU and TLB that normal instructions couldn't touch, and created
instructions software could execute.

So Digital kept that idea going.

-- 
Len Sorensen


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