6 ms·
The ARM Cortex-A55 is modern and in-order. Out-of-order CPUs tend to be large so if you want a small CPU you'll still go with in-order.
by muizelaar 8y ago
The ARM Cortex-A55 is modern and in-order. Out-of-order CPUs tend to be large so if you want a small CPU you'll still go with in-order.
- zozbot123 8y agoEnergy/power efficiency might be a more relevant concern than mere size - OOO execution is fast but energy intensive, for a given workload. (Granted, the latest process nodes might be a tad different, with "size" also impacting power consumption directly due to leakage currents. This stuff can get a bit complicated.)
- bogomipz 8y agoInteresting. Is lower power OOE an area of active research?
- Symmetry 8y agoWell, to the extent that improved process brings lower power it's an area of stupendous research investment. If you just mean architecturally there are people looking at ways to use less power by being less flexible but still get most of the benefit but it's not a huge topic.
- zozbot123 8y agoThe Mill processor architecture deserves mention here, as it basically aims to bridge VLIW-like low power usage with OOO-like performance. The way it attempts to do this is too complex to explain in a short comment, you can find detailed info on their website - but broadly-speaking it involves all sorts of 'tweaks' to ordinary VLIW, that ultimately result in something a bit different. (It should also be noted though that the initial, instruction decoding stages of a Mill-like 'belt' architecture are a lot closer to OOO than an ordinary VLIW. So the projected power savings would seemingly have to come from elsewhere - but they can be quite significant nonetheless, so the effort is projected to be worthwhile.)
- bogomipz 8y agoInteresting I remember hearing about this processor architecture. Is is still being actively developed? I didn't see much in the way of news on the Mill site.
- opencl 8y agoThere are a few recent forum posts indicating that they're still working on it at least, but it seems to be going extremely slowly. 5 years ago it had already been in development for 10 years and there was supposed to be silicon shipping in 2-3 years. 2 years ago they were talking about an FPGA prototype that has yet to show up.
- marcosdumay 8y agoI imagine (because there are not that many details on the Mill out there) that the power savings come mainly from: - A post-compiler compilation step that adapts a binary for a specific chip, replacing a complex hardware control module by a one-time software run, so the only thing actually on the chip is the routing; - A very nice set of primitives that push the non-determinism into data, instead of flow control. - Cheap interruptions, cheap memory access, and every other detail rethought to be cheap.