MacBook Pro performance issues w/2nd monitor and FCP7

Question

I have this MacBook Pro bought brand-new in January 2010:
  Model Name: MacBook Pro
  Model Identifier: MacBookPro5,2
  Processor Name: Intel Core 2 Duo
  Processor Speed: 3.06 GHz
  Number Of Processors: 1
  Total Number Of Cores: 2
  L2 Cache: 6 MB
  Memory: 8 GB
  Bus Speed: 1.07 GHz
and until today had never attached a second monitor to it. Today I hooked up my Samsung 24" to do some dual screen editing in Final Cut 7.0.3. I was unable to play back my video at full speed in the second monitor, and after a few seconds of skippy playback I'd get that error message about unable to play back video at full speed and to check my RT settings. I was using a Mini DisplayPort to DVI adapter. My computer has no issues playing the video in the laptop's monitor at any resolution and any quality settings (I've never changed the RT settings or anything else in the menu ever but I tried every combination this time). I then tried using my TV as a 2nd monitor with an HDMI adapter. Same performance issues. I then tried my friend's newer 13" MBP 8,1 and it performed flawlessly with the same project & footage. I feel like my $3,000 computer should outperform a $1,200 one even if mine is a year and a half older. Any advice?
Chris

Answer 1

Wow, you posted this perfectly to coincide with an identical problem, albeit using Logic Pro 9.1.5 rather than FCP.
Last week, I purchased a 23" external monitor to use alongside my "flagship" 2011 15" hi-res, 2.3 i7 Macbook Pro with 8Gb of RAM.
It is connected via a mini-DVI to D-sub analog (not that that should matter?) and all appeared fine.
The first issue I had was with my MBP's fan now running CONSTANTLY, when I have the second monitor attached. Even when the machine is completely idle.
When using the machine to record audio, this is a fairly hefty problem and not something I had anticipated - indeed why would I anticipate such a thing?
What is far, far worse though is that over the last few days I have had repeated problems with performance drop-outs and errors in Logic and I have trying to fathom out why. Realising that the only major system change made, was the above monitor connection, I ran some tests.
I restarted my MBP, no other apps were running and with my new 23" monitor attached acting as main display with MBP built in display on as secondary
I loaded up a fairly demanding Logic project which was hitting 40% to 60% CPU usage when using the built in MBP display last week
I ran activity monitor and had CPU usage history open
The above project now repeatedly overloads and playback halts in a given 8 bar section - with CPU at 80% most of the time
I disconnected the external display, no shut down, I just let the machine switch to the built in 15".
Started the same project, the same 8 bar section and hey presto - CPU usage back down to 40% to 60%
The above was reflected in the CPU usage history with the graph showing CPU use down by about a half, when running this Logic project WITHOUT the external display.
There is a very useful benchmark Logic project that has been used as a test by many users to gauge Logic performance on given Apple hardware.
The project has about 100 tracks pre-configured with CPU intensive plugins, designed to tax the CPU.
The idea is that you load up the project with tracks muted, press play and then unmute the tracks steadily until Logic us unable to play contiunously because of a system performance error.
On my MBP, with the external monitor NOT attached, I can play back around 50 of the audio tracks in this benchmark project.
With the monitor attached, I can get about 22 tracks playing.... which is actually a far worse a performance drop (-50% I think!?) than with the first example!
I did also try with just the external monitor attached and not the MBP display and performance was about 10% better than with dual monitors - so still extremely poor, to say the least.
This machine is the flagship MBP and has a dedicated AMD Radeon HD6750 GPU which should take care of most if not ALL graphics processing - I mean it's capable of running some pretty demanding games!
Putting aside the issue of constant fan noise, there is no reason AT ALL, why using an external monitor should tax the i7 CPU this way - it's not as though Logic is graphically demanding... far from it.
I am on 10.6.8, Logic 9.1.5, all apps up to date via "Software Update".
I will of course, be contacting Apple...