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Two GTX 690 PLX-related questions

Nov 23, 2020
249 (1.20/day)
Not Chicago, Illinois
System Name Desktop-TJ84TBK
Processor Ryzen 5 3600
Motherboard Asus ROG Strix B350-F Gaming
Cooling ARCTIC Liquid Freezer II 120mm, Noctua NF-F12
Memory B-Die 2x8GB 3200 CL14, Vengeance LPX 2x8GB 3200 CL16, OC'd to 3333 MT/s C16-16-16-32 tRC 48
Video Card(s) PNY GTX 692, EVGA GTX 650 Ti BOOST 2GB Superclocked Edition
Storage Crucial M4 128GB, Crucial MX500 500GB,WD 250GB, WD Black 2TB, WD Caviar Green 3TB, Intel Optane 16GB
Display(s) Samsung S22B350 1080p77, ASUS 1080p74
Case Rosewill CRUISER Black Gaming
Audio Device(s) SupremeFX S1220A
Power Supply Seasonic FOCUS GM-750
Mouse Kensington K72369
Keyboard Microsoft Comfort Curve 2000
Software Windows 10 Home 64-bit
Benchmark Scores are good
I'm currently working on updating my PNY GTX 690 with UEFI support. I found a tool supposedly from Inno3D that allows you to do that, and after confirming with Inno3D that it is in fact from them, I'm going to use it. I've hit a snag though. Note that my card reports NVidia being the subvendor - it's the same for MSI, Galax, Zotac, ASUS, etc. cards as far as I'm aware.

The GTX 690, being a dual-GPU card, has a PLX switch on board. A PEX8747 switch. This allows both GK104 dies to have "full" PCIe 3.0 16x connectivity. To give the 690 full UEFI support, I'll need to flash three files - two for the GPU dies, and one for the PLX switch.
I can flash the GTX 690 dies fine, but I can't access the PLX switch at all - not through nvflash, not through the tool, not through GPU-Z, etc. I can't see the PLX switch at all. The only reason I know it exists is because I saw it on the PCB.
I also don't know how I would go about flashing a new BIOS file to it. Would I have to buy a CH341A or similar programmer, tear the card down, clip it on to the PLX ROM, and flash it that way? Or is there a piece of software that can do it that I can't find?
This brings me to my other question - where is the UEFI-supporting PLX ROM/module? I can't find it.

Why UEFI support? I'd like to turn off CSM. I don't need it to boot Windows anymore as I had to reinstall as GPT (my old install was MBR, upgraded from W7), and the only thing limiting me is my graphics cards. Turning off CSM will also fix the weird resolution I get while running OpenCanopy, the GUI for OpenCore (I Hackintoshed my computer). It's scaled weird and doesn't look right, and turning off CSM does fix this.

If you need more info I'm happy to provide, if possible.