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y400 SLI


RedLionRisen

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I'm trying to get SLI up and running on a 650m y400 with windows 7, and I can't seem to get it working. The ultrabay fan comes on just fine. Only dxdiag shows a hint of there being a 2nd gpu, showing 4GB of display memory instead of 2 when the ultrabay is plugged in. No other program shows the ultrabay card. Not even nvidia control panel shows the SLI option, even after upgrading to the latest drivers. Is there something I have to change in the BIOS or what?

*EDIT*

This is all for being able to convert 650m cards to working 750m cards for use with 750m systems in SLI.

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https://forums.geforce.com/default/topic/615173/geforce-drivers/official-nvidia-331-40-beta-display-driver-feedback-thread-released-9-30-13-/post/3957733/#3957733

Disable UEFI as a temporary workaround. This stopped me from getting TDR's when gaming with SLI. Boot time increased by 1-2 seconds but otherwise no difference.

Oh yeah and this driver has been amazing for my BF3 performance. FPS increased by almost 20% and smoothness feels almost unreal. Game said I was getting 60 FPS before, but it felt like 40 FPS due to some mysterious input lag. Now it feels like 100 FPS even though I really only increased by 10-15 FPS. :) I guess whatever Nvidia did to optimize this driver for BF4 beta really makes a difference in BF3 since they use the same engine.

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Ok, I was an idiot. I just didn't have the ultrabay all the way in... hence why it was detected at all, and the fan wasn't actually running :P.

So... I've been experimenting, and here's what I've found:

Got y500 650m to operate in a y400 650m machine and run SLI no problem.

Ultrabay 650m can be force flashed with 750m BIOS, but it appears there may not be a change in the actual device ID. After successfully flashing, it still shows up as a 650m in the system (with 650m drivers installed I guess), and SLI seems like it still functions. I've no idea if the device/board id would present a problem if such a card were put into a 750m system. I don't have a 750m system to test with...

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https://devtalk.nvidia.com/default/topic/489965/cuda-programming-and-performance/gtx480-to-c2050-hack-or-unlocking-tcc-mode-on-geforce/4/

Hopefully svl7 can chime in on this topic. The above link describes using nvflash to change the device id in the gpu's software via softstraps. I've looked at what I believe are the appropriate device IDs for the 650 and 750m cards, and they differ only by the last two digits, which I understand is the limit for possibly being able to change the device ID without hardware modifications to the chip itself. The device ID of the chip must be changed, along with the BIOS, to fully transform a 650m into a 750m, and have it read correctly by the system so that a once 650m ultrabay can be used as a 750m ultrabay in SLI with a y410/510. I believe the straps command described above looks at certain lines in the software and changes those bits to modify the device ID on the software level (as opposed to changing the pins/transistors). It's unknown if this method will work with these newer cards, but it's definitely worth a shot.

I could run the commands myself, but I don't have an actual 750m ultrabay to get the info from. I could use someone's help in that...

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