Hardware Reference
In-Depth Information
Table 7.7 Multiword (16-Bit) DMA Modes and Transfer Rates
Note that multiword DMA modes are also called
busmaster DMA modes
by some man-
ufacturers. Unfortunately, even the fastest multiword DMA Mode 2 results in the same
16.67MBpstransferspeedasPIOMode4.However,eventhoughthetransferspeedisthe
same as PIO, because DMA offloads much of the work from the processor, overall sys-
tem performance is higher.Even so,multiword DMA modes were never very popular and
have been superseded bythe newer Ultra-DMA modes supported in devices that are com-
patible with ATA-4 through ATA-7.
Table 7.8
shows the Ultra-DMA modes now supported in the ATA-4 through ATA-7 spe-
cifications. Note that you need to install the correct drivers for your host adapter and ver-
sion of Windows to use this feature.
Table 7.8 Ultra-DMA Support in ATA-4 Through ATA-7
SATA
With the development of ATA-8, it seems that the PATA standard that has been in use for
more than 10 years has finally reached the end of the line. Sending data at rates faster
than 133MBps down a parallel ribbon cable is fraught with all kinds of problems because
