failing ATI Radeon 2600XT ahead?

[williemyers]

hey guys...
My MacPro 3,1 has been successfully using it's ATI Radeon 2600XT to drive 2 x 25" ASUS monitors for about 3 years now. That would be under OSX 10.8.5 or OSX 10.11.3.
Now, occasionally on restarts - or some bootups - the "secondary" monitor shows nothing, reports "DVI no signal" and goes to sleep. The "primary" monitor (the one with the menu bar) has no such problems.
I have switched monitors and cables in all possible combinations to make sure that it's not a monitor or cable issue. I have removed & reseated all memory and the GPU and no difference. I have run extended AHT and it shows no problems.
Does it sound like I have a video card about to die?

thanks in advance

[mikehalloran]

How old is your NV RAM battery? If you can't remember, that would be the second thing I'd try since you have done the first already.

If the old one is a BR2032, it may be original and way past due. Fortunately, a Mac Pro tower takes the common CR2032 with no problem (BR is better in high heat like the 2013+ Mac Pro or 2011+ iMac) If you can't see the trick for removing the old one easily, there are YouTube videos.

If, instead, the video would go down when warm, I'd suspect overheating but your issue is when booting making the NV RAM battery an inexpensive suspect.

If you've recently replaced the battery, the card begins to look likely.

[williemyers]

damn, Mike, I didn't know that the Mac's PRAM had a wafer battery!
(makes sense though...duh...)

User manual, pg. 64....Easy enough to replace...
(this is getting embarrassing!)

on it first thing tomorrow. Thanks *very* much for that!