Fuel XIO 12V Bias low; XIO 5V high - where to measure?


New member
Oct 9, 2021
I'd like to verify if I have to replace the env monitoring chips in my Fuel. Where can I measure XIO 12V Bias and XIO 5V?

If I have to replace the DS1780, does anyone here know which one is responsible for the two voltages above?


Feb 4, 2019
Western United States
I have not seen this information anywhere unfortunately, possibly someone else has? Only a mapping of the DS1780 to NODE temperature sensors: https://cz7asm.blogspot.com/2021/03/replacing-monitoring-chips-on-sgi-fuel.html

From the site above:

Note on the Vin pins 14-18, at least you could narrow down the voltage input to the chip, and one of the chips could be monitoring XIO 5V and 12V Bias? Maybe the 0 or 1 chip (in the image of the linked site above), given it being XIO?
Screen Shot 2021-10-09 at 10.26.48 PM.png

If you're suspicious about specific inputs to one of the chips I could try to measure what they are from a working Fuel for comparison purposes. Although some of them are packed in pretty tight, so it might be difficult.


Active member
Jan 13, 2020
Seattle, WA
Those voltage rails you want are read by the DS1780 ON THE GRAPHICS CARD, I've confirmed this on IrixNet via my fuel rebuild. Without a graphics card installed your L1 will be missing ALL XIO voltages. So what plugs INTO the XIO port is what measures it. The smaller port of the two on the XIO provides the voltages.

Also if you have a burnt out DS1780 on your graphics card (which HAPPENS, it seems to be directly related to a short on the XIO rails, for me it was 12V XIO bias, but I never found out which component was shorted as it stopped when I did a 1.5W 1V injection to look for it , I've not returned to the card yet).

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