Andor Technology iXon Ultra 897 User Manual page 57

DATA ACQUISITION
This is faster and more reliable than making use of the virtual memory feature of the
operating system (which simulates extra physical memory using a buffer on the hard
drive to hold data larger than would normally fit in the RAM available) because
Andor's Virtual Memory system is specifically designed to handle the large file you
are attempting to load and work with in the MCD application.
Whereas the operating system's virtual memory management is attempting to
"guess" which data should be held in physical memory, and which should be cached
to the buffer, based on data traffic, Andor Virtual Memory knows exactly how to
handle the large file being opened in MCD.
There are three simple choices for you to make when the Virtual Memory dialog
opens. First, a tick box enables/disables Andor Virtual Memory.
Secondly, you may set a Threshold value. This is the file size in megabytes above
which Virtual Memory will be used. Many of your data series might well fit
normally into the physical memory of your computer, in which case using Virtual
Memory carries no speed advantage. Set this value to reflect the size of your
computer's RAM initially. You may find that you need to lower the threshold if you
often have other applications running, or open multiple data files in MCD at one
time, as these activities can cause there to be less physical memory available than
you expect. Generally, the lower the threshold value, the faster large files will open.
However, if a large kinetic series is held in virtual memory it may be somewhat
slower to step through or 'play' as a movie, compared to the same file opened
without virtual memory.
Finally, you must choose a hard drive Location where the Virtual Memory buffer
will reside. It is important that you choose a location on a LOCAL hard drive
(ideally an uncompressed volume), because the speed of file access across a network
connection may be much slower than to a local hard drive – thus negating the speed
advantage of using Virtual Memory.
Section 4 . 4
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