AOpen AP5TC User Manual page 86

Frequently Asked Questions
CPU, and slow down the CPU speed as well as warning when temperature
is high then a predefined temperature. (Normally, 55 degree C.)
Q: What is the Ultra DMA/33?
A: This is the new specification to improve IDE HDD data transfer rate. Unlike
traditional PIO mode, which only uses the rising edge of IDE command
signal to transfer data, the DMA/33 uses both rising edge and falling edge.
Hence, the data transfer rate is double of the PIO mode 4 or DMA mode 2.
(16.6MB/s x2 = 33MB/s).
The following table lists the transfer rate of IDE PIO and DMA modes. The
IDE bus is 16-bit, which means every transfer is two bytes.
Mode Clock per
33MHz
PCI
PIO mode 0 30ns
PIO mode 1 30ns
PIO mode 2 30ns
PIO mode 3 30ns
PIO mode 4 30ns
DMA mode 0 30ns
DMA mode 1 30ns
DMA mode 2 30ns
DMA/33 30ns
A-4
Clock Cycle Data Transfer rate
count time
20 600ns (1/600ns) x 2byte = 3.3MB/s
13 383ns (1/383ns) x 2byte = 5.2MB/s
8 240ns (1/240ns) x 2byte = 8.3MB/s
6 180ns (1/180ns) x 2byte = 11.1MB/s
4 120ns (1/120ns) x 2byte = 16.6MB/s
16 480ns (1/480ns) x 2byte = 4.16MB/s
5 150ns (1/150ns) x 2byte = 13.3MB/s
4 120ns (1/120ns) x 2byte = 16.6MB/s
4 120ns (1/120ns) x 2byte x2 = 33MB/s