Transmeta's Crusoe processors

[Jaap van Ganswijk <ganswijk@xxxxxxxxx>]

FYI,

This is about the new 'x86-compatible' processors
from Transmeta, the company that Linus Thorvalds
is currently working for.

Greetings,
Jaap

PS. See my comments at the end.


Source:
http://www.transmeta.com/crusoe/technology.html


Transmeta has pioneered a revolutionary new approach
to microprocessor design. Rather than implementing the
entire x86 processor in hardware, the Crusoe processor
solution consists of a compact hardware engine
surrounded by a software layer.

The hardware component is a very simple,
high-performance, low-power VLIW (Very Long
Instruction Word) engine with an instruction set that bears
no resemblance to that of x86 processors. Instead, it is
the surrounding software layer that gives programs the
impression that they are running on x86 hardware. This
innovative software layer is called the Code Morphing
software because it dynamically "morphs" (that is,
translates) x86 instructions into the hardware engine's
native instruction set.

Transmeta's software translates blocks of x86 instructions
once, saving the resulting translation in a translation cache.
The next time the (now translated) code is executed, the
system skips the translation step and directly executes the
existing optimized translation at full speed. 

This unique approach to executing x86 code eliminates
millions of transistors, replacing them with software. The
current implementation of the Crusoe processor uses
roughly one-quarter of the logic transistors required for an
all-hardware design of similar performance. This offers the
following benefits:

The hardware component is considerably
smaller, faster, and more power efficient
than conventional chips.

- The hardware is fully decoupled from the
  x86 instruction set architecture, enabling
  Transmeta's engineers to take advantage of
  the latest and best in hardware design trends
  without affecting legacy software.

- The Code Morphing software can evolve
  separately from hardware. This means that
  upgrades to the software portion of the
  microprocessor can be rolled out
  independently of hardware chip revisions.

Transmeta's Code Morphing technology is obviously not
limited to x86 implementations. As such, it has the
potential to revolutionize the way microprocessors are
designed in the future.

For more info see:
http://www.transmeta.com/


--- My comments:
The concept reminds a lot of how x86 programs were
being executed on the Alpha architecture under NT, with
the help of '32!FX'. The difference however seems to be
that the 32!FX worked as a kind of in the OS integrated
interpreter/translator for applications, whereas in the
Crusoe the interpreter/translator is integrated in a sort of
sub-BIOS, so the translation proces is transparant for the
real BIOS and the OS.

The 32!FX already worked remarkably well (for most of
the applications) but it's drawbacks were the slow manner
in which native x86 applications would start up (because
they had to be translated first or compared with translation
data on the harddisk) and the amount of extra DRAM that
was needed for the interpretor/translator. Of cause playing
modern games using such a translator was asking for trouble.

It seems however that in the Crusoe (and with the current
amounts of available DRAM) these problems have been
solved much better. I wonder what it will cost and what the
benchmarks will say. I also wonder if it will be possible to
run native applications on the processor and how fast
those will run compared to x86 programs...


Groeten/Greetings,
Jaap

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