VOGONS

Unwanted CPU overvolting on 440BX motherboard

Topic actions

First post, by Paar

Posted on 
User metadata
Rank Member
Rank
Member

Hi. I have a Soyo SY-6BA+ III motherboard which overvolts my CPUs a little by default. Measured by the board itself in the BIOS and by multimeter on voltage regulator. I wonder what the reason is. I guess it's caused by old caps which are out of spec after all of those years, but they look great otherwise (visually).
When using a 2V Katmai CPU, the output voltage is 2.04V. When using 1.75V Coppermine, the output voltage is 1.77-79V (fluctuates). I'd like to fix the board so it outputs correct voltage, especially when using Deschutes/Katmai CPUs, as those can get hot.

Is my guess correct that old caps can cause the issue? I don't want to recap the board if not necessary.

Reply 1 of 4, by rasz_pl

Posted on 
User metadata
Rank l33t
Rank
l33t

is that with multimeter of onboard diagnostics? .04V is pretty much measurement error, wouldnt worry about it.

https://github.com/raszpl/FIC-486-GAC-2-Cache-Module for AT&T Globalyst
https://github.com/raszpl/386RC-16 memory board
https://github.com/raszpl/440BX Reference Design adapted to Kicad
https://github.com/raszpl/Zenith_ZBIOS MFM-300 Monitor

Reply 2 of 4, by Paar

Posted on 
User metadata
Rank Member
Rank
Member

Measured one of the regulators next to the CPU slot. I have another board which produces a little smaller deviancy, but it's still off.

Reply 3 of 4, by myne

Posted on 
User metadata
Rank Oldbie
Rank
Oldbie

2.04 is margin of error.

It's 2% off perfect which is fine. Every vrm ever fluctuates within defined tolerances which are most likely 5-10%.

If you really want to waste a few hours though, look up the edge connector VID pins and see if you can tape it off down to 1.9 or 1.95v

Looks like you can't tape for less
https://web.archive.org/web/20060622200013/ht … ts/24445209.pdf

Pg19

I built:
Convert old ASUS ASC boardviews to KICAD PCB!
Re: A comprehensive guide to install and play MechWarrior 2 on new versions on Windows.
Dos+Windows 3.11+tcp+vbe_svga auto-install iso template
Script to backup Win9x\ME drivers from a working install
Re: The thing no one asked for: KICAD 440bx reference schematic

Reply 4 of 4, by Paar

Posted on 
User metadata
Rank Member
Rank
Member

Okay, I won't be doing the recapping then. Thanks for your opinions!

Go to top of page Go to top of page
Back to General Old Hardware
Close window
Close window