NVIDIAs 64-bit Tegra K1: The Ghost of Transmeta Rides Again, Out of Order 125
MojoKid (1002251) writes Ever since Nvidia unveiled its 64-bit Project Denver CPU at CES last year, there's been discussion over what the core might be and what kind of performance it would offer. Visibly, the chip is huge, more than 2x the size of the Cortex-A15 that powers the 32-bit version of Tegra K1. Now we know a bit more about the core, and it's like nothing you'd expect. It is, however, somewhat similar to the designs we've seen in the past from the vanished CPU manufacturer Transmeta. When it designed Project Denver, Nvidia chose to step away from the out-of-order execution engine that typifies virtually all high-end ARM and x86 processors. In an OoOE design, the CPU itself is responsible for deciding which code should be executed at any given cycle. OoOE chips tend to be much faster than their in-order counterparts, but the additional silicon burns power and takes up die area. What Nvidia has developed is an in-order architecture that relies on a dynamic optimization program (running on one of the two CPUs) to calculate and optimize the most efficient way to execute code. This data is then stored inside a special 128MB buffer of main memory. The advantage of decoding and storing the most optimized execution method is that the chip doesn't have to decode the data again; it can simply grab that information from memory. Furthermore, this kind of approach may pay dividends on tablets, where users tend to use a small subset of applications. Once Denver sees you run Facebook or Candy Crush a few times, it's got the code optimized and waiting. There's no need to keep decoding it for execution over and over.
Re:Is it better? (Score:4, Insightful)
What's flaky about it?
The advantage of decoding and storing the most optimized execution method is that the chip doesn't have to decode the data again; it can simply grab that information from memory.
Re:Is it better? (Score:5, Insightful)
In-order processors are a better choice as long as your program is well optimized.
Optimizing for in-order processors is difficult, and not something that is going to be done for 99% of programs. It's also very difficult to do statically.
NVIDIA has chosen to let the optimization be done by software at runtime. That's an interesting idea that will surely perform very well in benchmarks, if not in real life.
Re:Sounds smart, but is it? (Score:4, Insightful)
A JVM does nothing like that.
It is. The Hotspot JVM compiles bytcode to assembly with optimizations on the fly. It also has some capability to re-optimize based on runtime performance and usage patterns.