7
TLDR: The BIOS shows voltages as vcore: 1.248, 12V: 12.566, 5V: 5.160, 3.3V: 3.424. Is this bad?
I got one miniITX motherboard that supports a 19 V laptop input instead of the regular ATX connector/PSU. The motherboard manual says the input should be 19 V ±10% = from 17.1 V to 20.9 V.
When I use the board with a 500 W seasonic PSU via ATX connectors, the voltages are all almost right on the specification (12.0 V, 5.0 V, and 3.3 V), but when using the 19 V external 90 W power brick (which provides 19.3V when tested without any load on) I get the voltages:
- 12.513 ~ 12.566 (jumps from one value to another. Always those two numbers)
- 5.088 ~ 5.160 (oscillates between those two. Most of the time it is at 5.136)
- 3.408 ~ 3.424 (oscillates)
- With a vcore of 1.240 ~ 1.248 (like 12 V, jumps from one to another)
Is that bad? I tried running the PC like that and Debian installed fine. No hicups. Will that lower the life of any component? Will it all go down in a ball of fire eventually?
The outlet measures a total draw of under 30 W (30 at peak) from the power brick. So it is nowhere near its rated 90 W output (and it is from a know brand, so not a cheap overmarked knockoff).
(I put overclocking on the tags to reach people that may know better about this :) - although I am not overclocking. The motherboard doesn't even allow it.)
- Motherboard: http://www.asrock.com/mb/AMD/AM1H-ITX/
- CPU: AMD 5350
- RAM: HX316C9SR/8 (PDF!)
edit: those numbers are from the BIOS screen. i can't log them over time because those sensors are not supported in linux yet... sigh. but they do not seem to change with board temperature (i.e. running for a few hours and then rebooting and looking at the numbers on the BIOS). but i can't ever check them while under actual load.
10% has always been concidered acceptable, I set warnings for such things at 5% , and some of this stuff can be off almost 20% before there is a real problem (because of additional conversions going on) . How did you read the voltages though? the 3 easy ones, you can get a volt meter out and you will see the sencors themselves reading voltages to programs are not 2 digit accurate? – Psycogeek – 2015-08-16T18:39:20.343
These numbers are within spec. ±5% is okay, and motherboards are built to accept these tolerances. Some variation under load is also normal. There should be absolutely no harm to the computer from these voltages. – bwDraco – 2015-08-16T18:54:42.177
Voltage readings from internal sensors in computers are not reliable. If you want accurate values, use a calibrated multimeter. – Daniel B – 2015-08-16T22:26:01.897
As others have mentioned, you seem to be referencing data from the motherboard's integrated power monitoring systems. These measurements are typically both inaccurate and imprecise. Inaccuracy is due to the use of cheap sensors, and effects like Vdroop. The reason you see values jumping back and forth between two precise looking values is because there are no discrete "steps" in between them. It knows about 12.513V, and 12.566V, but anything in between gets rounded to the closest of the two.
– bcrist – 2015-08-16T23:34:45.750Where more precise values are needed the motherboard will have voltage regulators for each component that needs them, like the CPU and RAM. See also https://en.wikipedia.org/wiki/Voltage_regulator_module
– Zan Lynx – 2015-08-17T03:59:31.247@DanielB how do i go about probing a live computer for those voltages? are there standard test pads in any spec? remember that i am NOT using the ATX 24 pin connector, but a 19V laptop brick. so the actual "PSU" is integrated somewhere in the motherboard. i wouldn't even know where to probe. – gcb – 2015-08-17T18:14:55.080
1@gcb You could use the on-board SATA power connector. It provides a wide range of different voltages to measure and have fun. ;) – Daniel B – 2015-08-17T19:42:21.840
i'm not sure it is enabled when the 19V is used. the manual says using both will fry the motherboard. i will probe the voltage sources... shouldn't hurt if i stay clear of the ON pin... i guess. – gcb – 2015-08-17T22:10:07.207
2Read again: “When you use the DC-in power adapter, please use the onboard SATA power connector to get the power for HDDs.” – Daniel B – 2015-08-18T06:40:27.370