| This package contains a
program that can be used to test DMA transfer rates and errors. Our PCI
boards transfer images to PC memory by DMA (Direct Memory Access). If the
PCI bus on your computer is overloaded, you will generate DMA errors when
transferring frames. This program will help you find the threshold where
your PCI bus begins to be overloaded. That will give you a good idea of
how many frame grabbers you can safely use on your system.
DMATEST provides input
displays at the top of the screen and output displays at the bottom of
the screen with global parameters and program controls in the center of
the screen.
The program will list
as many frame grabbers as it finds, up to 4 in the input boxes at the
top of the screen. You can set the test parameters for each frame grabber
by changing the width and height. You can also enable or disable a
frame grabber if you would like to test fewer than the total found
in your machine.
The test results are
displayed in the output boxes at the bottom of the screen. The main
field to watch in the boxes at the bottom is the DMA ERRORS. Our boards
always transfer at real time, but not always without errors. The errors
depend on the conflicts on the PCI bus. For successful transfers you
should get ZERO errors.
You can slow down the
screen updates by setting the update rate to 1 or more seconds. Anything
beyond 10 will not make any difference. This will take some traffic off
the PCI bus.
You can select
"Cache Hits" at any time even when the program is running. Selecting
"Cache Hits" will simulate running a program while grabbing frames and
will add traffic to the PCI bus. In general, if you are testing several
frame grabbers and not generating any DMA errors, you should enable the
"Cache Hits" to determine whether you are on the threshold of generating
DMA errors. If enabling "Cache Hits" generates errors, then you are on
the threshold. If not, then you are probably safe to run that number of
frame grabbers in a real situation without generating DMA errors.
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