Crusoe Exposed: Transmeta TM5xxx Architecture 2

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It should be noted that many of the ideas and internal implementations used in the TM32xx and TM5xxx chips were not even invented by Transmeta, despite what their patents appear to claim.

While I will not give a full analysis here, it appears that much of Transmeta’s work was actually invented by IBM Research in the early 1990s. IBM’s Daisy (Dynamically Architected Instruction Set from Yorktown) project [6] is essentially CMS for the PowerPC architecture, and uses a strikingly similar design and implementation, including:

  • Designing the morph host microarchitecture with the same semantics as the target instruction set (in IBM’s case, PowerPC rather than x86)
  • Translated page cache, using a T-bit buffer to track which user pages are dirty and need re-translation
  • Explicit memory alias handling, using protected loads and checked stores
  • Extensive profiling logic to aid in further optimization
  • Handling of speculatively reordered loads and stores to I/O space

Even more similarities between CMS and IBM’s work can be found in [8] and [9], which details BOA, a high clock speed VLIW successor to Daisy specifically intended for runtime binary translation of PowerPC systems.

Of course, Transmeta was still unquestionably the first to fully solve the thorny problem of transparent x86 binary translation in a commercially successful manner. With that in mind, many of the basic ideas expressed in Transmeta’s patents appear to have substantial prior art in Daisy, and its successor, BOA [8], [9].

However, since BOA is a newer effort, it is not clear where the initial ideas came from. The current situation is that both IBM and Transmeta appear to have conflicting patents on the same technology, with the only difference being the x86 versus PowerPC specific aspects.

The similarities between Transmeta’s and IBM’s work is easy to prove, since the Daisy firmware has been released as open source [6]. IBM even acknowledges this apparent similarity in [7], but notes that Transmeta has failed to provide any internal details to verify this claim [7], [8], [9]. Perhaps this report will shed some light on this mystery.

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