The command cat /proc/dma will show you what?
A.
Whether DMA is enabled
B.
Which DMA channels are in use
C.
Which DMA mode is in use
D.
General information about DMA on the machine
Explanation:
/proc/dma contains a list of the registered ISA direct memory access (DMA) channels in use. It shows whether DMA is enabled or not.Example
# cat /proc/dma
4: cascade
Answer should be A.
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DMA Addresses
Direct memory addressing (DMA) is an alternative method of communication to I/O ports. Rather than have the CPU mediate the transfer of data between a device and memory, DMA permits the device to transfer data directly, without the CPU’s attention. The result can be lower CPU requirements for I/O activity, which can improve overall system performance.
To support DMA, the x86 architecture implements several DMA channels, each of which can be used by a particular device. To learn what DMA channels your system uses, examine the /proc/dma file:
$ cat /proc/dma
2: floppy
4: cascade
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Correct answer is B
See info about /proc/dma here[1]
[1] http://linux-training.be/files/books/html/fun/apcs04.html#idp8289712
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Correct answer is B
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