When early 2011 MBP is connected to external monitor, there are some flickering pixels

[That_Damn_Kid]

There's several pixels that randomly flicker. It's the external monitor that is doing this. Is it possible the display port is going bad? Or maybe I just need a new cable?

I tried my Windows laptop and the external monitor didn't have any pixel flickering.

 

[keysofanxiety]

If you've got the 15" or 17", they have issues with the graphics failing. So it could possibly be early signs of that.

If you've got the 13", you can try reset PRAM/SMC, shut down with reopen windows when logging back in disabled and ensure you're on the latest OS. Of course the same advice applies to the 15/17, but with those machines the problem you've describes is leaning towards dGPU failure.

I assume you used the same cable for your Windows laptop? That would help isolate where the issue is.

 

[That_Damn_Kid]

It's the 13". I used a VGA cable for my Windows laptop, DVI cable/DVI mini display port cable for my Macbook.

 

[vddobrev]

Based on my experience, this problem may be due to bad cable or bad RAM.

 

[keysofanxiety]

It's the 13". I used a VGA cable for my Windows laptop, DVI cable/DVI mini display port cable for my Macbook.

Ah OK. Almost certainly the cable then.

As Vddo said, it could be the RAM as the VRAM is shared with system RAM, so RAM hiccups on iGPU machines occasionally exhibit themselves as odd graphics artefacts. However you'd almost certainly be noticing kernel panics or some other unorthodox problems if that were the case. Providing the RAM fitted in your machine is 1333MHz then I'll double-down on waging it's the cable.