Hardware emulation raises its head, again

Although it isn't labelled as such, new technology from Transitive amounts to hardware emulation. It's impressive but far from fully tested, writes Manek Dubash

Transitive has announced new hardware emulation technology and an agreement with two SGI software developers to use it.

Dubbed QuickTransit, Transitive’s technology allows software compiled for one processor and operating system to run on another, with changes in neither source nor binary code. In other words it’s a hardware emulator, although the company is careful not to mention the word emulation — hardly surprising given the number of failed emulation attempts that litter IT’s history books.

Previous failures include Digital’s FX32, which ran x86 software on Alpha chips, and Transmeta’s attempt to run x86 code on its low-power Efficeon processors. Instead of emulation, Transitive is calling its technology “hardware virtualisation”.

What makes it significant is that Apple has been testing QuickTransit for months, as Steve Jobs has confirmed. Calling the technology Rosetta, Apple intends to build it into its OS when it ships its first x86-based Macs next year.

“Apple made the switch to Intel because they had translation software — the risk is enormous and they tested this before they decided to make the move,” says Transitive’s chief technology officer and founder, Alisdair Rawsthorne.

According to Rawsthorne, the technology works by translating CPU instructions on the fly, building a list of translated instructions into a code cache. On second execution, instructions are pulled from the cache. The system also optimises sections of code that it detects are frequently called on. The result is a 20% performance penalty for the emulation and a 25% memory overhead, Rawsthorne says. Graphics tasks experience a lower overhead and CPU-intensive ones much higher, possibly up to 40%.

I saw a demo and briefly tried the system, switching between applications written for x86 and running on an SGI MIPS machine and vice versa, and x86 applications running on a Power5-based Apple G5. In its favour, in all cases, the user interface’s response was as fast as it would be if it were native. An onscreen 3D image was manipulated with no visible performance deterioration. However, there were also no benchmarks and I ran no CPU-intensive tasks, nor were any applications that hadn’t been pre-loaded tested.

If the demonstration is typical, then this is the best manifestation of this technology that we’ve seen. This is a big if, though, and I remain sceptical given the poor track record of hardware emulation and would like to see it given a more thorough workout.

Hardware emulation inside a virtual machine looks like an attractive option from a server and development perspective and Transitive chief executive Bob Wiederhold says the company is talking to VMware with this in mind. Transitive also intends to sell QuickTransit as a retail product at some point in the future.

Could this be the right moment for hardware emulation? Given the speed of today’s hardware, a performance penalty of even 40%could, from an end-user perspective, make little difference to many applications. However, compatibility is a big issue and Apple is not claiming 100% compatibility for Rosetta, although Transitive mentioned no such caveats.

The company, which developed the technology at the UK’s Manchester University and conducts its R&D there, has its headquarters at Los Gatos, California. Transitive was set up in 2000, after five years of development effort at Manchester University, and has raised some US$24 million (NZ$35 million) in three rounds of venture capital funding. It has approximately 65 employees.

Transitive recently announced Opticore and UGS as ISV partners.

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