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direct memory access
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What is the meaning of PMA in tellabs 8110 modem?
DMA Stands for -- Deferred Maintenance Alarm PMA Stands for -- Prompt Maintenance Alarm Ashish Kumar Nawada, Bihar
When was DMA Distribuidora created?
DMA Distribuidora was created in 1950.
When was DMA - magazine - created?
DMA - magazine - was created in 1993.
When did DMA - magazine - end?
DMA - magazine - ended in 2003.
What types of operations is DMA used to accelerate?
DMA operations
Does a DMA channel bypass the CPU?
Yes, DMA does bypass the CPU.
How is DMA different that busmastering?
DMA is the same thing as bus-mastering.
Generally which transfer mode is faster DMA or PIO?
DMA transfers data directly from the drive to memory without involving the CPU. PIO involves the CPU and is slower than DMA mode.
How many DMA channels are in AT class?
There are 8 DMA channels in an AT class computer.
How many DMA channels are supported by Windows XP?
8 DMA Channels .
What is DMA structure?
Using interrupts driven device drivers to transfer data to or from hardware devices works well when the amount of data is reasonably low. For example a 9600 baud modem can transfer approximately one character every millisecond ( 'th second). If the interrupt latency, the amount of time that it takes between the hardware device raising the interrupt and the device driver's interrupt handling routine being called, is low (say 2 milliseconds) then the overall system impact of the data transfer is very low. The 9600 baud modem data transfer would only take 0.002% of the CPU's processing time. For high speed devices, such as hard disk controllers or ethernet devices the data transfer rate is a lot higher. A SCSI device can transfer up to 40 Mbytes of information per second. Direct Memory Access, or DMA, was invented to solve this problem. A DMA controller allows devices to transfer data to or from the system's memory without the intervention of the processor. A PC's ISA DMA controller has 8 DMA channels of which 7 are available for use by the device drivers. Each DMA channel has associated with it a 16 bit address register and a 16 bit count register. To initiate a data transfer the device driver sets up the DMA channel's address and count registers together with the direction of the data transfer, read or write. It then tells the device that it may start the DMA when it wishes. When the transfer is complete the device interrupts the PC. Whilst the transfer is taking place the CPU is free to do other things. Device drivers have to be careful when using DMA. First of all the DMA controller knows nothing of virtual memory, it only has access to the physical memory in the system. Therefore the memory that is being DMA'd to or from must be a contiguous block of physical memory. This means that you cannot DMA directly into the virtual address space of a process. You can however lock the processes physical pages into memory, preventing them from being swapped out to the swap device during a DMA operation. Secondly, the DMA controller cannot access the whole of physical memory. The DMA channel's address register represents the first 16 bits of the DMA address, the next 8 bits come from the page register. This means that DMA requests are limited to the bottom 16 Mbytes of memory. DMA channels are scarse resources, there are only 7 of them, and they cannot be shared between device drivers. Just like interrupts the device driver must be able to work out which DMA channel it should use. Like interrupts, some devices have a fixed DMA channel. The floppy device, for example, always uses DMA channel 2. Sometimes the DMA channel for a device can be set by jumpers, a number of ethernet devices use this technique. The more flexible devices can be told (via their CSRs) which DMA channels to use and, in this case, the device driver can simple pick a free DMA channel to use. Linux tracks the usage of the DMA channels using a vector of dma_chan data structures (one per DMA channel). The dma_chan data structure contains just two fields, a pointer to a string describing the owner of the DMA channel and a flag indicating if the DMA channel is allocated or not. It is this vector of dma_chan data structures that is printed when you cat /proc/dma
How do you get onto anti-dma?
anti-dma code is a code that disables bad egs
