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Towards that end does anyone know if there any ATX power supplies that will stream out their sensor info over a serial port or something? It'd be nice to have

Towards that end does anyone know if there any ATX power supplies that will stream out their sensor info over a serial port or something? It'd be nice to have power monitoring on that side of the mainboard's power regulators and caps, to pick up marginal issues before they get filtered out, and the power supplies these days will have a little ucontroller with all that information anyway without the mainboard having to duplicate that monitoring circuitry in the right place. For what's such an important piece of a computer there's so little introspection for data while in use that has to be being collected regardless. Yeah, you can always hook up a oscope or what have you, but catching it in the act of being marginal early on would have saved me more hours in my life than I'd like to admit.

daper 5y ago
Server PSUs support such communication (looks like this is PMBus protocol, variation of SMBus, which is variation of I²C). In servers it's connected to the BCM and usually allows to read input and output power, FAN speed, temperatures and status (good/bad). The BCM often records historical data, including peak power (in last 1h, 24h), etc. After quick searching is looks there are people reading this info with a MCU [1]. But I think it would be hard to find such PSU in ATX form factor. [1] https://github.com/sxjack/dps750tb_psu_i2c https://github.com/sxjack/dps750tb_psu_i2c
dendriti 5y ago
Whenever I experience issues which are likely related to a power supply, it is much easier to drop in a known-good replacement than to spend time diagnosing the specific issues. Also better to remove a potentially faulty PSU before it damages much more expensive hardware.
- monocasa 5y ago
  The typical failure modes mean that it'll be marginal for a while, and should be able to give you information before it goes fully bad. Being able to have introspection before it goes fully bad is what I want, as I hope to have some data before it even makes it's way on to a bench. The power clients (mainboard, GPUs, disk drives, etc) normally know they're getting pretty bad power from a PSU and filter it heavily to smooth it out. It'd be nice to know if the voltage is occasionally dropping and it's just being covered up by downstream caps that are over provisioned to just smooth out not fully rectified AC.
jrockway 5y ago
I had a Corsair power supply with this feature. The system I built with it was quite flaky, but I could reproduce the failure and eventually debugged a 12V transient dropout (when running AVX workloads) that was the cause of the flakiness. The built-in monitoring didn't help at all; doesn't update frequently enough, and the computer crashed by the next USB polling cycle anyway. I used an oscilloscope. I don't really have enough data to outright blame the power supply. I don't think I connected all of the 12V lines to the motherboard (power supply didn't come with enough cables), and I can't be sure that the motherboard was designed properly for a mildly-overclocked 6950X (VRM banks, capacitors near the CPU, etc.) It was all enough of a pain that I will never buy another Corsair power supply. My current best practices involve only buying Seasonic power supplies, and connecting every possible "optional" power connector to the motherboard. If the PSU doesn't come with enough cables to do that, buy them separately. My current Threadripper motherboard has a 6-pin and 2 4-pin ATX12V connectors, and a Molex connector. Many are marked "optional" in the motherboard's instruction manual, but I have them connected anyway. Probably overkill. Great stability. Without having designed the system or the test scenario, skipping optional things sounds like the sort of thing that's going to cost you a lot of time at some random point in the future. Best to avoid, even if you look like an idiot to the EE that designed the board.
jlgaddis 5y ago
IIRC, Corsair's AXi and HXi series power supplies -- basically, the really expensive ones! -- support PMBus (I2C). The entry-level and lower-priced ones don't, AFAIK.
R0b0t1 5y ago
The data isn't necessarily collected. Many existing supplies use hardware counters or PWM modules to control the power output at a level very close to hardware.
- monocasa 5y ago
  In both of those cases there's a feedback loop setting the PWM dynamically. Even the error term of the PID or what have you would be super helpful.
  - R0b0t1 5y ago
    There is no PID loop in the sense you mean. It's a hardware counter module that feeds a flip flop. There might be a free running ADC that is used to compare match against the counter module, or sometimes it's just a binary input like the AC signal zero crossing. You don't need a CPU core to do this, and the older, cheaper parts do not necessarily have a CPU in them. There are even (iirc, very uncommon) designs with no digital logic save the switching.
dogben 5y ago
Corsair AXi and HXi series. They even got upstream kernel support: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/hwmon/corsair-psu.c https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin... Here is my output from lm-sensors $ sensors corsairpsu-hid-3-1 Adapter: HID adapter v_in: 230.00 V v_out +12v: 12.00 V v_out +5v: 5.00 V v_out +3.3v: 3.00 V psu fan: 0 RPM vrm temp: +49.0°C case temp: +40.0°C power total: 96.00 W power +12v: 80.00 W power +5v: 16.00 W power +3.3v: 8.00 W curr in: N/A curr +12v: 6.00 A curr +5v: 3.00 A curr +3.3v: 2.00 A

daper 5y ago

Server PSUs support such communication (looks like this is PMBus protocol, variation of SMBus, which is variation of I²C). In servers it's connected to the BCM and usually allows to read input and output power, FAN speed, temperatures and status (good/bad). The BCM often records historical data, including peak power (in last 1h, 24h), etc. After quick searching is looks there are people reading this info with a MCU [1]. But I think it would be hard to find such PSU in ATX form factor. [1] https://github.com/sxjack/dps750tb_psu_i2c https://github.com/sxjack/dps750tb_psu_i2c

dendriti 5y ago

Whenever I experience issues which are likely related to a power supply, it is much easier to drop in a known-good replacement than to spend time diagnosing the specific issues. Also better to remove a potentially faulty PSU before it damages much more expensive hardware.

monocasa 5y ago
The typical failure modes mean that it'll be marginal for a while, and should be able to give you information before it goes fully bad. Being able to have introspection before it goes fully bad is what I want, as I hope to have some data before it even makes it's way on to a bench. The power clients (mainboard, GPUs, disk drives, etc) normally know they're getting pretty bad power from a PSU and filter it heavily to smooth it out. It'd be nice to know if the voltage is occasionally dropping and it's just being covered up by downstream caps that are over provisioned to just smooth out not fully rectified AC.

jrockway 5y ago

I had a Corsair power supply with this feature. The system I built with it was quite flaky, but I could reproduce the failure and eventually debugged a 12V transient dropout (when running AVX workloads) that was the cause of the flakiness. The built-in monitoring didn't help at all; doesn't update frequently enough, and the computer crashed by the next USB polling cycle anyway. I used an oscilloscope. I don't really have enough data to outright blame the power supply. I don't think I connected all of the 12V lines to the motherboard (power supply didn't come with enough cables), and I can't be sure that the motherboard was designed properly for a mildly-overclocked 6950X (VRM banks, capacitors near the CPU, etc.) It was all enough of a pain that I will never buy another Corsair power supply. My current best practices involve only buying Seasonic power supplies, and connecting every possible "optional" power connector to the motherboard. If the PSU doesn't come with enough cables to do that, buy them separately. My current Threadripper motherboard has a 6-pin and 2 4-pin ATX12V connectors, and a Molex connector. Many are marked "optional" in the motherboard's instruction manual, but I have them connected anyway. Probably overkill. Great stability. Without having designed the system or the test scenario, skipping optional things sounds like the sort of thing that's going to cost you a lot of time at some random point in the future. Best to avoid, even if you look like an idiot to the EE that designed the board.

jlgaddis 5y ago

IIRC, Corsair's AXi and HXi series power supplies -- basically, the really expensive ones! -- support PMBus (I2C). The entry-level and lower-priced ones don't, AFAIK.

R0b0t1 5y ago

The data isn't necessarily collected. Many existing supplies use hardware counters or PWM modules to control the power output at a level very close to hardware.

monocasa 5y ago
In both of those cases there's a feedback loop setting the PWM dynamically. Even the error term of the PID or what have you would be super helpful.
- R0b0t1 5y ago
  There is no PID loop in the sense you mean. It's a hardware counter module that feeds a flip flop. There might be a free running ADC that is used to compare match against the counter module, or sometimes it's just a binary input like the AC signal zero crossing. You don't need a CPU core to do this, and the older, cheaper parts do not necessarily have a CPU in them. There are even (iirc, very uncommon) designs with no digital logic save the switching.

dogben 5y ago

Corsair AXi and HXi series. They even got upstream kernel support: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/hwmon/corsair-psu.c https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin... Here is my output from lm-sensors $ sensors corsairpsu-hid-3-1 Adapter: HID adapter v_in: 230.00 V v_out +12v: 12.00 V v_out +5v: 5.00 V v_out +3.3v: 3.00 V psu fan: 0 RPM vrm temp: +49.0°C case temp: +40.0°C power total: 96.00 W power +12v: 80.00 W power +5v: 16.00 W power +3.3v: 8.00 W curr in: N/A curr +12v: 6.00 A curr +5v: 3.00 A curr +3.3v: 2.00 A