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I'm hoping that someone else has possibly encountered this before so that they understand what I'm describing.

My wife and I just moved to a new place and the movers haven't arrived with our stuff yet; so I've been using an ancient laptop for the past few days. This laptop generally works more or less OK as long as I don't have more than one or two programs running at a time (this has got 512 Mb of RAM, so I've really got to take it easy).

Sometimes, though, it seems that if I "overwork" it somewhat, this strange thing will happen: I'll move a window, and suddenly it will seem as if the entire OS is frozen. But watching carefully will reveal that the screen is actually refreshing very slowly -- to the extent where I can visibly see the image on the monitor being drawn, almost line-by-line, from top to bottom.

This is rather bizarre from my perspective since the graphics performance of the system in general is fine. Most of the time, there is no visible sluggishness. So what's going on here? And more importantly, are there well-known steps one can take to fix this problem?

Mostly I'm just curious if anyone knows what the explanation for this graphical anomaly is.

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up vote 3 down vote accepted

I've had this. I believe the programs you are using require more ram. Information has been moved out of ram and has to be accessed from the hard drive. So all available ram is being used and so the window can only get a small amount of info at a time.

I'm not an expert so someone may have a more accurate answer.

Regards,

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Exactly. Out of RAM and most likely the display adapter is sharing what little there is with the system. Feed it RAM! –  boot13 Aug 20 '10 at 5:12
    
This makes sense to me. AND I am very happy to hear it as I just upgraded my 512 Mb to 2 Gb! So far, it definitely seems much better. –  Dan Tao Aug 24 '10 at 0:34
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I believe its not the memory pressure but the CPU.

When there is not enough memory, the system sends unused and underused memory to disk, to be called back when a program needs its memory back. (This is called "paging.")

When the memory is critically low - a real memory shortage - then the system starts to spend all of its time sending memory pages to disk and pulling them back off of disk. (This is called "thrashing.") When this happens, you'll see your hard disk light go solid as it spends all of its time reading and writing, and the CPU starts spending all of its time doing this shuffle.

When the CPU is busy, it can't redraw the screen as fast as it should. In the most extreme cases, the system becomes unresponsive as it spends its time moving data to and from disk.

The best way to resolve this problem without rebooting is to kill a large process that is unnecessary and thus free up memory. When memory is freed, the thrashing stops and the CPU can get back to doing useful work.

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