Tweet
So. I have a A8-5500 desktop APU @ 3.2 GHz (3.7 turbo), Debian 64 bit, Xfce 4.10 (no composite) and i wanted to try the new OSS stuff. I have installed:
- kernel 3.11 (now rc4)
- mesa (9.3 devel) from git
- radeon X driver from git
- libdrm.
Everything works mostly well - VDPAU, OpenGL. TF2 runs better than on fglrx. Essentially when im at the computer everything is fine.
1. voltage regulation, temps and throttling - The APUs are a complete CPU+GPU unit, they share the same power envelope so keeping it low requires more factors at play - seems that the video driver directly influences the CPU part too.
Example - the older radeon driver kept the effective CPU frequencies at the very minimum (~1.4 GHz) DESPITE cpuinfo showing 3.2 GHz (highest official p-state), altogether with a constant 1.34-1.44 V CPU voltage resulting in heat and slow CPU.
Now, the new radeon with the new userspace stuff changed it.
- The A8-5500 works between 0.875 and 1.475 V according to specs.
- In practice, with the fglrx driver is 0.9-1.44 V.
- With radeon, its between 0.9 and 1.34 - also it has a bit lower temps on load than fglrx, but somewhat lower effective frequencies, according to cpufreq-aperf - also thermal throttling is more pronounced (fglrx keeps the ~3.2 GHz, radeon drops sometimes below it, but has ~5C lower temps). - With a single loaded thread, the upper frequencies are the same for fglrx and radeon (reaching max 3.488 GHz, despite the theoretic 3.7 turbo spec).
Temps:
- idle 14-15C with fglrx - dont take this for granted, its obviously not real, the thing is that in these CPUs the temperature sensors show accurate temps when loaded. I use it for reference. Loaded temps go up to ~60C (default cooler! @ ~26-28C roomtemp).
- idle 16-17 with radeon. Loaded temps go up to ~55-57. (the older radeon had ~28-57C and was slow as hell).
- CPU Performance is somewhat lower with radeon - because of lower speeds caused by more paranoid throttling. I dont know this is good or bad (performance vs lower temp).
Bugs/quirks:
- The most annoying bug - i have set xscreensaver to dpms after 4 minutes. It worked like this since i have Linux on my computer, no issues.
Now, it goes into dpms and comes back if needed, but if left alone for more than just minutes (hours, half hour, varies) of idle time the computer just becomes unresponsive (both console and network), i have to reboot from the power button (forced). Nothing in the logs (except the usual stuff, and i could roughly pinpoint the time it worked before freezing from there).
Disabling dpms solved this issue - but i really want it back since my rig is up 24/7 and just blanking the monitor still leaves it permanently on.
Now i upgraded everything (kernel to rc4, mesa and x server from git), i will see if it changed anything...
- Right after boot, the voltage stays at ~1.34V (sometimes briefly 1.44) - idle temp is ~28 C. Changing to another vt and back (or doing a dpms off-on cycle) brings it down to 0.9 (it changes dynamically afterwards, but it goes only up to 1.34V) and temps down to what i reported above.
- kernel 3.11 (now rc4)
- mesa (9.3 devel) from git
- radeon X driver from git
- libdrm.
Everything works mostly well - VDPAU, OpenGL. TF2 runs better than on fglrx. Essentially when im at the computer everything is fine.
1. voltage regulation, temps and throttling - The APUs are a complete CPU+GPU unit, they share the same power envelope so keeping it low requires more factors at play - seems that the video driver directly influences the CPU part too.
Example - the older radeon driver kept the effective CPU frequencies at the very minimum (~1.4 GHz) DESPITE cpuinfo showing 3.2 GHz (highest official p-state), altogether with a constant 1.34-1.44 V CPU voltage resulting in heat and slow CPU.
Now, the new radeon with the new userspace stuff changed it.
- The A8-5500 works between 0.875 and 1.475 V according to specs.
- In practice, with the fglrx driver is 0.9-1.44 V.
- With radeon, its between 0.9 and 1.34 - also it has a bit lower temps on load than fglrx, but somewhat lower effective frequencies, according to cpufreq-aperf - also thermal throttling is more pronounced (fglrx keeps the ~3.2 GHz, radeon drops sometimes below it, but has ~5C lower temps). - With a single loaded thread, the upper frequencies are the same for fglrx and radeon (reaching max 3.488 GHz, despite the theoretic 3.7 turbo spec).
Temps:
- idle 14-15C with fglrx - dont take this for granted, its obviously not real, the thing is that in these CPUs the temperature sensors show accurate temps when loaded. I use it for reference. Loaded temps go up to ~60C (default cooler! @ ~26-28C roomtemp).
- idle 16-17 with radeon. Loaded temps go up to ~55-57. (the older radeon had ~28-57C and was slow as hell).
- CPU Performance is somewhat lower with radeon - because of lower speeds caused by more paranoid throttling. I dont know this is good or bad (performance vs lower temp).
Bugs/quirks:
- The most annoying bug - i have set xscreensaver to dpms after 4 minutes. It worked like this since i have Linux on my computer, no issues.
Now, it goes into dpms and comes back if needed, but if left alone for more than just minutes (hours, half hour, varies) of idle time the computer just becomes unresponsive (both console and network), i have to reboot from the power button (forced). Nothing in the logs (except the usual stuff, and i could roughly pinpoint the time it worked before freezing from there).
Disabling dpms solved this issue - but i really want it back since my rig is up 24/7 and just blanking the monitor still leaves it permanently on.
Now i upgraded everything (kernel to rc4, mesa and x server from git), i will see if it changed anything...
- Right after boot, the voltage stays at ~1.34V (sometimes briefly 1.44) - idle temp is ~28 C. Changing to another vt and back (or doing a dpms off-on cycle) brings it down to 0.9 (it changes dynamically afterwards, but it goes only up to 1.34V) and temps down to what i reported above.
Comment