Re: Transmeta ;)

[Al Hudson <nospam [at] york.ac.uk>]

On Thu, 20 Jan 2000, Alastair Donlon wrote:

> From my reading of their docs, the translation software which morphs
> instructions on the fly will be on a Rom, which will mean that you
> won't be able to _easily_ shift between different instruction sets.
> It will require a FLASH upgrade.

Not quite. Firstly, the morphing software only morphs x86 code, so
currently the question is pretty academic. But, there is no reason for the
code to be in flash ROM. The 3120 is ROM-based, because it is designed for
an embedded system: Mobile Linux is ROM based, and talks to the morphing
software at boot time. However, remapping is done all the time, as is
shadowing. Your video card, for instance, has a rom in it. That ROM is
almost certainly shadowed into main memory. With an MMU, it doesn't matter
whether the address is different, because the RAM pages can be mapped in
over the ROM pages.

I would expect most implementations of Crusoe technology to use memory
shadowing technology. For a start, ROM is *much* slower than RAM, unless
you're using expensive ROM. The technology is very different. I would
imagine, due to the criticality of the morphing (75% of the processor,
remember ;), it would be implemented as quickly as possible. Also, you
want to page the Flash ROM out of addressable space as quickly as
possible, to reduce the hazard of virii ;) (This applies to Trojans as
well, I guess).

Cheers,

Alex.

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