Optiplex 780 & GTX 660 GPU issue

Question

Hello folks! New face in town here with very interesting problem.

Not the PC freak myself, but I'm by no means "dumb" when it comes to IT hardware.

As stated above, I own Optiplex 780 and recently I upgraded it's q6600 processor with q9500 and everything works just fine. Then I decided to go for gpu upgrade and my friend had a spare GPU and without even thinking there might be some issues I just bought it (very stupid of me, ik)

I currently run on 1gb ATI AMD Radeon R7 200 Series Saphire.

Card I bought is GeForce GTX 660 2gb Palit.

First thing I did was a mistake not to check it's required power supply. I ran it on existing 280W PSU and it restarted my PC several time and actually worked.

I tested it in Elder Scrolls Online and fps was around 90 BUT sometimes it would stutter a lot and during that period sound was also defective... like that slow motion noise or whatever.

When I saw that happening I turned PC off and after that I cant turn it on with GTX 660. I unplug it and plug older AMD R7 and it works fine.

First assumption - not enough power! I need bigger PSU.

I tried with 300W, 500W and 550W and it didn't work. All mentioned PSU worked just fine with AMD R7.

After that I decide to check if, maybe somehow, I damaged GTX 660 with low power supply. I tested on 550W at my friend's place and it works just fine.

We both were stunned... had (still have ) no idea why it wont work with my OptiPlex 780.

After that I decided to look for professional help. There is company in my town which does the PC sales and repairs and I went to check the problem with them.

Their guy placed few months (alot newer card than both I own atm) old GPU into my PC with their MS PSU of 550W and it worked. After that he puts in GTX 660 and it doesn't work We just looked at ourselves with that "how tf" look in our eyes.

GTX 660 WORKS, it's not faulty... yet it somehow just wont work in my Optiplex 780 after that first time it worked after few restarts. It doesn't even show the image on monitor like it does on other configurations.

After that he assumed it might be BIOS issue. He told me he will flash my BIOS tomorrow and give me a call if it solves the problem.

As you might assume, me being here means it didn't solve the problem and he thinks my motherboard isn't compatible with this GeForce GTX 660.

I asked him how he explains the thing when it actually worked for like 1 hour at least.... he just shrugged

Its really interesting issue and, if nothing else, I'd like to know definite answer on how and why it worked in the firstplace and now it works on every other PC and just won't work on mine??

Current specs i'm running as I'm writing this:

Operating System
Windows 10 Pro 64-bit
CPU
Intel Core 2 Quad Q9500 @ 2.83GHz 36 °C
Yorkfield 45nm Technology
RAM
8,00GB Dual-Channel DDR3 @ 531MHz (7-7-7-20)
Motherboard
Dell Inc. 0C27VV (CPU)
Graphics
Acer X193HQ (1366x768@60Hz)
1024MB ATI AMD Radeon R7 200 Series (Sapphire/PCPartner) 29

Owondyah · Answer

Yea, I knew I'll miss something

I did use molex to sata connector from PSU into the GPU and PSU really is 255W, as you stated (took a second look and spotted my mistake)

I'll try CMOS thing tmrw and come back with reply.

Generally, you are saying motherboard - gpu compatibility isn't an issue?

And... isn't 255W kinda too little for this GPU ehh ?

redxps630 · Answer

GTX 660 requires a 6 pin power connector from psu. Your report of using it in 780 with ?280W psu is curious. how did you run it without the 6 pin? afaik the stock psu in 780MT does not have 6 pin. Also stock psu in MT is either 255W or 305W. Is your psu the stock from Dell?

If you did somehow run the card without 6 pin, most times as soon as power is on motherboard would sound a screeching siren, warning that no discrete power connected to gpu. It is strange that there is no such reported. Unless you somehow adapted the 280W sata connectors to make a custom 6 pin. Please clarify what you did.

If somehow you ran the card without 6 pin connected (whatever psu you use), 780 is not running the card properly. It wants to send video to dGPU that it has detected, but dGPU is not powered properly. Instead of flashing bios, try reset CMOs jumper on 780 motherboard, then make sure you connect a 6 pin to gtx 660 and test again. If all along you have connected the 6 pin, then idk. I would still suggest reset CMOs jumper. This is much safer than flashing bios.

redxps630 · Answer

780 motherboard and gtx660 are both legacy, but they are compatible with each other. I had a similar gtx650 working with a Dell motherboard of same era.  Gtx660 requires minimum psu of 450w. 255W is too weak. No matter how you adapt molex to make a 6 pin, the psu is just unable to power both motherboard, cpu, and discrete gpu.

Owondyah · Answer

I did try with friend's 500W and it didn't work either... I'll try again when I get him to borrow me that PSU again + cmos thing     Thanks!

redxps630 · Answer

When you borrow a used 550W psu from someone, first test it in 780 without gtx660 installed.  Use integrated VGA for this test.  If POSTs well, then try install gtx660 and connect a genuine 6 pin to it.  You should then observe no more video from integrated VGA. This is an indirect evidence that 780 has detected a dGPU and has disabled on board VGA.  At that time test gtx660 video port.

Owondyah · Answer

I have no idea how but I got it to work...

What I did was:

As my monitor is, like entire PC, legacy VGA I took hdmi cable from ps4 and connected PC with my TV...

There was "no signal" message for like minute or two and then picture appeared. I was finaly able to see something on screen after that first time with GPU inserted in my PC.

After that I went back and connected it to my monitor. Same happened, expect the fact that message on my monitor was different. Minute or two "no cable connected" and after that picture appeared.

I'm using 500W PSU atm.

I installed drivers from this link - https://www.nvidia.com/en-us/drivers/results/66884/

I have no idea what I did... how it wasn't working back then... simply clueless. I'll come back tomorrow with edit or repost about if it restarts my PC few times again after "longer downtime".

So far did few regular restarts due to drivers installation and it all went perfectly fine.

Owondyah · Answer

So yea... i'm back as promised, with the update.

Yes it indeed runs, but it always requires restarts and at least minute of black screen with "cable not connected" message before I get it to work.

Weird stuff and I have no idea what is caused by that.... Could it be that I need even bigger PSU?

redxps630 · Answer

Does it run smoothly otherwise after restart and initial no video error?  If yes, it does not sound like the card is underpowered.  500W psu should be good enough assuming it is not a no name brand.

Owondyah · Answer

Every time before it runs, it requires 2 restarts.

After that I runs just well.... some issues in ESO (company logos on start are kinda slowed down, everything in the game runs so far so good).

Now it started immediately after second restart. Didn't need that extra minute to load the picture.

Owondyah · Answer

sorry for double post but I feel like I need to tell you also that I tried Conqueror's Blade on it and it cutscenes are in slow motion with sound included...

This is first time I see something like this... I know the game can lagg, but SOUND to lagg and appear like some "digital noise"... I can't find words to describe how it sounds and it sounds like that just on moments something big and intense happens...

Literally every cutscene in Conquerors Blade is slow motion and super "digitalized" sounds of voiceovers and music...

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Optiplex 780 & GTX 660 GPU issue

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