This problem is solved. See my post 2nd post below
About a month ago I bought two Dell Optiplex 760 MTs. Both systems are exactly the same in every way and work very well.
Last week, I bought a Dodocool 2-port USB 3.0 PCIe x1 expansion card from ebay and it works on both Optiplex 760 PCs when placed in either the PCIe x1 or x16 slots.
However, on only one of the systems, it's a hit or miss as to whether the BIOS detects the card from a cold start up (the BIOS detects all the PCIe slots, just sometimes not this particular card – it will just show "empty", when it should say "USB").
As a result, if the BIOS doesn't detect the card, then it's not available in Windows when Windows loads in. Therefore, when I start the PC, I always have to enter the BIOS to see if the card is detected before windows boots.
If BIOS shows the card, fine, I just exit the BIOS and let the PC boot into Windows and all is fine. But if the BIOS doesn't detect the card, I have to exit the BIOS, push the power button on the tower to shut the system off, then power on again and usually the card is recognized (sometimes might take 2 or 3 tries but many times only one).
It never happens if I simply do a restart from the OS. On a restart, the BIOS always remembers/sees/detects the card. It only happens if I do a shutdown and have to power-up the system using the power button on the tower.
This problem happens only with this one system and only with this particular PCIe card and not any others and it doesn't matter if it is installed in the PCI x1 or PCI x16 slot – the problem is the same. No problems on either PCIe slot with any other PCIe cards.
I have tried many, many, many times to replicate this problem on the other identical PC but I cannot replicate it.
At first I thought it was a defective mobo or defective PCIe x1 slot but when I saw that it also happens on the PCIe x16 slot and all other PCIe cards I've tried have no problem, I don't think I can conclude it is a bad mobo or slot(s).
I also don't see how it is a defective PCIe card since it works flawlessly on one system. In fact, it works on both systems, just that in one the BIOS might not detect it.
I'm hoping someone here can shed some light.
Here is a list of everything I have tried…
Flashed the BIOS 3 times now.
Tested voltages both PSUs under load. Both systems' voltages tested out fine.
Ran the command "bcdedit /set CONFIGACCESSPOLICY DISALLOWMMCONFIG" in Safe Mode with command prompt. I did this because I read an old thread from another forum for a similar problem and this fixed that person's problem. But it did not fix my problem.
Reset the CMOS
Changed CMOS battery with fresh one, even though the old one tested at over 3v
- Dell Optiplex 760 MT
- Nanya 6GB DDR2 PC2-6400 (800MHz) RAM
- Intel Core 2 Duo 3.0GHz E8400 Wolfdale CPU
- Dell Inc. 0M858N mobo
- Dell BIOS vA16
- Windows 7 Pro 64-bit SP1
(using on-board GPU)