By: Doug S (foo.delete@this.bar.bar), September 13, 2021 10:57 am
Room: Moderated Discussions
--- (---.delete@this.redheron.com) on September 13, 2021 11:19 am wrote:
> - one thing Apple do (I don't know about other designs) is slide voltage up and down while keeping frequency
> unchanged. Obviously changing frequency is somewhat disruptive in a way that changing voltage is not.
> Apple have some flexibility to do this given the digital power estimators, a knowledge of the capacitance in
> the system, and an ability to prevent catastrophe if the system is oversubscribed by having instruction issue
> paused by the DPE for a cycle or two. Maybe also the fact that every SRAM is decoupled from logic with a voltage
> shifter between the two, so you have flexibility to down-voltage logic while not losing SRAM retention.
> (At least they have a long sequence of patents about this, so you'd hope it's implemented!)
I'm a little confused on this point. Why would you want to alter voltage while keeping frequency constant? Shouldn't you always want to run at the lowest voltage capable of handling a given frequency to minimize power? In what circumstance would you for example want to increase voltage while keeping frequency constant? That makes no sense to me, but maybe I'm missing something.
> - one thing Apple do (I don't know about other designs) is slide voltage up and down while keeping frequency
> unchanged. Obviously changing frequency is somewhat disruptive in a way that changing voltage is not.
> Apple have some flexibility to do this given the digital power estimators, a knowledge of the capacitance in
> the system, and an ability to prevent catastrophe if the system is oversubscribed by having instruction issue
> paused by the DPE for a cycle or two. Maybe also the fact that every SRAM is decoupled from logic with a voltage
> shifter between the two, so you have flexibility to down-voltage logic while not losing SRAM retention.
> (At least they have a long sequence of patents about this, so you'd hope it's implemented!)
I'm a little confused on this point. Why would you want to alter voltage while keeping frequency constant? Shouldn't you always want to run at the lowest voltage capable of handling a given frequency to minimize power? In what circumstance would you for example want to increase voltage while keeping frequency constant? That makes no sense to me, but maybe I'm missing something.
Topic | Posted By | Date |
---|---|---|
alder lake. | inteluser | 2021/09/10 01:52 AM |
alder lake. | Andrei F | 2021/09/10 09:31 AM |
alder lake. | Andrey | 2021/09/10 09:38 AM |
alder lake. | rwessel | 2021/09/10 11:18 AM |
alder lake. | Andrei F | 2021/09/10 12:49 PM |
alder lake. | Andrey | 2021/09/10 04:12 PM |
alder lake. | David Hess | 2021/09/10 07:39 PM |
alder lake. | Andrey | 2021/09/11 12:28 AM |
alder lake. | --- | 2021/09/10 05:24 PM |
alder lake. | Andrei F | 2021/09/12 01:09 AM |
DVFS | David Kanter | 2021/09/12 09:58 PM |
DVFS | Andrei F | 2021/09/13 01:02 AM |
DVFS | Anon | 2021/09/13 03:28 AM |
DVFS | Jukka Larja | 2021/09/13 05:35 AM |
DVFS | Andrei F | 2021/09/14 12:07 AM |
DVFS | Jukka Larja | 2021/09/14 04:11 AM |
DVFS | Andrei F | 2021/09/14 07:55 AM |
DVFS | Jukka Larja | 2021/09/14 10:23 AM |
DVFS | --- | 2021/09/13 10:19 AM |
DVFS | Doug S | 2021/09/13 10:57 AM |
DVFS | David Hess | 2021/09/13 11:32 AM |
DVFS | --- | 2021/09/13 01:06 PM |
DVFS | David Hess | 2021/09/13 02:21 PM |
DVFS | David Kanter | 2021/09/15 03:05 PM |
DVFS | David Hess | 2021/09/13 11:46 AM |
DVFS | Jukka Larja | 2021/09/14 04:35 AM |
Quick shutdown? | David Kanter | 2021/09/15 10:46 AM |
Quick shutdown? | Andrei F | 2021/09/16 07:12 AM |
Quick shutdown? | David Kanter | 2021/09/16 11:04 AM |
Quick shutdown? | Andrei F | 2021/09/17 01:35 AM |
Quick shutdown? | Andrei F | 2021/09/17 01:38 AM |
and weren't 'they' right? | Daniel B | 2021/09/13 04:20 AM |
and weren't 'they' right? | Andrei F | 2021/09/13 04:51 AM |
and weren't 'they' right? | Daniel B | 2021/09/13 06:29 AM |
and weren't 'they' right? | anon | 2021/09/13 05:07 AM |
and weren't 'they' right? | Jukka Larja | 2021/09/13 05:26 AM |
and weren't 'they' right? | anon | 2021/09/13 11:37 PM |
Alder Lake has no little cores | Heikki Kultala | 2021/09/13 06:33 AM |
Alder Lake has no little cores | Michael S | 2021/09/13 07:33 AM |
Alder Lake has no little cores | me | 2021/09/13 10:45 AM |
Alder Lake has no little cores | Heikki Kultala | 2021/09/13 01:49 PM |
Alder Lake has no little cores | anon | 2021/09/13 11:42 PM |
why stop at two core sizes? | hobold | 2021/09/14 05:47 AM |
Memory caches did this, right? | Mark Roulo | 2021/09/14 02:51 PM |
Memory caches did this, right? | Brett | 2021/09/14 07:17 PM |
Memory caches did this, right? | Kevin G | 2021/09/16 03:10 PM |
Large reorder buffers (L1+L2) | ⚛ | 2021/09/15 11:24 AM |
Large reorder buffers (L1+L2) | hobold | 2021/09/15 12:06 PM |
Alder Lake has no little cores | Adrian | 2021/09/14 08:33 AM |
and weren't 'they' right? | David Hess | 2021/09/13 12:00 PM |
Battery vs Performance | Mark Roulo | 2021/09/13 12:18 PM |
Battery vs Performance | Doug S | 2021/09/13 02:05 PM |
Battery vs Performance | David Hess | 2021/09/13 02:28 PM |
Battery vs Performance | --- | 2021/09/13 05:08 PM |
Battery vs Performance | --- | 2021/09/13 05:08 PM |
Battery vs Performance | Doug S | 2021/09/13 08:53 PM |
Battery vs Performance | Anon | 2021/09/14 06:42 AM |
and weren't 'they' right? | Daniel B | 2021/09/13 12:57 PM |
and weren't 'they' right? | David Hess | 2021/09/13 02:11 PM |
and weren't 'they' right? | --- | 2021/09/13 02:38 PM |
and weren't 'they' right? | --- | 2021/09/13 02:32 PM |
and weren't 'they' right? | Brendan | 2021/09/14 03:30 AM |
and weren't 'they' right? | Jukka Larja | 2021/09/14 04:31 AM |
and weren't 'they' right? | Etienne Lorrain | 2021/09/14 12:29 AM |