-5v Power Error on 2 different Asus MB's (p2b p3b-f)- why? \ VOGONS

-5v Power Error on 2 different Asus MB's (p2b p3b-f)- why?

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First post, by jfarms

Posted on 2023-05-07, 00:02

jfarms Offline

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Hi,

I started testing two ASUS slot 1 mb's, a p3b-f rev 1.10 and a p2b 1.04. My PSU is a CX450 from a couple years ago (after ridiculous research on a budget tier PSU- it was well-reviewed). On both of these MB's, I get a warning during boot saying there is a hardware monitor error. These are the p3b-f screen: https://imgur.com/a/iDyMxUP . On every boot I have to hit f1 to proceed past the error, basically, and the fact that it's a -5v problem appears in the BIOS hardware monitor. On the p2b, it just says 0.0V[Err] for the -5v rail in the BIOS hardware monitor. CPU is p2-450.

Any idea why this could be happening? I had no errors/issues with this PSU before, and was running it in a p3 1000 socket 370 gigabyte board the day before I started using it for these ASUS boards. There are no spinning disks- just an ide-microsd and two CD drives).

(these are the power specs for the PSU- error persists with a TNT2 or a voodoo 5500 for agp graphics- it's 15w for 5vsb and 110 for 3.3v and 5v rails:

Power Specs
Rail 3.3 V 5 V 12 V 5 VSB -12 V
Max. Power 20 A 20 A 37.4 A 3 A 0.3 A
110 W 448.8 W 15 W 3.6 W
Total Max. Power 450 W

Reply 1 of 4, by auron

Posted on 2023-05-07, 00:24

auron Offline

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newer ATX supplies don't provide -5V anymore, that's why you are getting that error. ignore it and turn the monitoring for that voltage off, it's not needed other than for some old sound cards.

however, your readouts demonstrate why in my view using these newer group-regulated PSUs on old boards is a bad idea: the 3.3V rail is at 3.46V which is just about right within 5% ATX spec tolerance, but could very well go out of spec depending on how much the other rails are loaded. since you are not even using an HDD you are basically running something a bit like those crossload scenarios in PSU tests - essentially no load on 12V and everything on 5V/3.3V, while the PSU is designed for the opposite scenario.

Reply 2 of 4, by jfarms

Posted on 2023-05-07, 00:33

jfarms Offline

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auron wrote on 2023-05-07, 00:24:

newer ATX supplies don't provide -5V anymore, that's why you are getting that error. ignore it and turn the monitoring for that voltage off, it's not needed other than for some old sound cards.

however, your readouts demonstrate why in my view using these newer group-regulated PSUs on old boards is a bad idea: the 3.3V rail is at 3.46V which is just about right within 5% ATX spec tolerance, but could very well go out of spec depending on how much the other rails are loaded. since you are not even using an HDD you are basically running something a bit like those crossload scenarios in PSU tests - essentially no load on 12V and everything on 5V/3.3V, while the PSU is designed for the opposite scenario.

Thanks- not having -5v would explain it.

It's actually not group regulated- it's DC-DC from CWT iirc. That said, the crossload point is fair- is there a specific type of newer PSU that you would particularly recommend for this retro usecase? And when you mention 'old sound cards'- how old are you talking- sb pro? sb16? or earlier?

Reply 3 of 4, by Horun

Posted on 2023-05-07, 00:46

Horun Offline

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Early SB cards before SB16 and Media Vision require -5v, there are also a few others but not many. Yes you should always load the PSU major feeds with at least 10% of max, most of us put an old HD just to make sure the +5v and +12v get enough load to be stable if the only other thing is a motherboard+vid card...

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 4 of 4, by jfarms

Posted on 2023-05-07, 00:53

jfarms Offline

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Horun wrote on 2023-05-07, 00:46:

Early SB cards before SB16 and Media Vision require -5v, there are also a few others but not many. Yes you should always load the PSU major feeds with at least 10% of max, most of us put an old HD just to make sure the +5v and +12v get enough load to be stable if the only other thing is a motherboard+vid card...

That's really helpful- thanks! I'll be sure to add one of my spinning disks- I've certainly got a bunch 🤣. It was just so much easier to backup and restore microsd cards I stopped using them.

I never had any stability issues running the skt 370 p3 with 3 sound cards and a v5 with this same psu, but I'm retiring the skt 370 to use slot 1 instead for the 440bx chipset. Is there a real chance of the 110w of 5v not being enough for this kind of system?

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