3 ms·
I think everyone is blowing past the real story here. A72 cores are 10% slower than A73 per clock. A510 is also supposed to be around 10% slower than A73 -- a
by hajile 5y ago
I think everyone is blowing past the real story here.
A72 cores are 10% slower than A73 per clock.
A510 is also supposed to be around 10% slower than A73 -- about the same performance as A72.
The big difference is that A72 is out-of-order while A510 is in-order. This means that A510 won't be vulnerable to spectre, meltdown, or any of the dozens of related vulnerabilities that keep popping up.
For the first time, we can run untrusted code at A72 speeds (fast enough for most things) without worrying that it's stealing data.
- amatecha 5y agoInteresting, and great point. Curious to see the first SBCs using these :) (FWIW Cortex-A710 is still out-of-order pipeline, if anyone was wondering) Spec pages: A510: https://developer.arm.com/ip-products/processors/cortex-a/cortex-a510 https://developer.arm.com/ip-products/processors/cortex-a/co... A710: https://developer.arm.com/ip-products/processors/cortex-a/cortex-a710 https://developer.arm.com/ip-products/processors/cortex-a/co...
- phire 5y agoIn-order CPUs aren't automatically immune to speculative execution exploits. ARM's A8 core is an example of an in-order core that was vunable. It's speculative execution that causes problems, and in-order CPUs still do speculative execution during branch prediction. It's just that they typically get through less instruction while speculating. All you need for Spectre is a branch misperception that lasts long enough for a dependent load. However, it's been over three years since ARM have known about Meltdown and Spectre. There is a good chance the A510 is explicitly designed to be resistant to those exploits.
- pertymcpert 5y agoIn order cores can't use branch prediction?
- amatecha 5y agoInterestly, I think they do (I don't know much about them). ARM's own infographic[0] says "In-order design with 'big-core' inspired prefetch & prediction", not sure if that's the same branch prediction we're talking about in regards to Spectre, etc. [0] https://community.arm.com/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-21-42/CPU-blog-image2.JPG https://community.arm.com/cfs-file/__key/communityserver-blo... from https://community.arm.com/developer/ip-products/processors/b/processors-ip-blog/posts/first-armv9-cpu-cores https://community.arm.com/developer/ip-products/processors/b...
- Symmetry 5y agoThey do but almost no in order design can manage to load a value from memory and then launch another load from the location based on that value before the branch resolves and the speculation is aborted. IIRC the Cortex A8 and Power 6 are the only two in order processors vulnerable to Specter.
- mhh__ 5y agoSpectre is because computers are memory bound so branch prediction without being able to touch memory is useless, and touching memory is very hard to undo, not because of out of order execution as per se.