Frequently Asked Questions
A-4
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
Clock
count
Cycle
time
Data Transfer rate
PIO mode 0
30ns
20
600ns
(1/600ns) x 2byte = 3.3MB/s
PIO mode 1
30ns
13
383ns
(1/383ns) x 2byte = 5.2MB/s
PIO mode 2
30ns
8
240ns
(1/240ns) x 2byte = 8.3MB/s
PIO mode 3
30ns
6
180ns
(1/180ns) x 2byte = 11.1MB/s
PIO mode 4
30ns
4
120ns
(1/120ns) x 2byte = 16.6MB/s
DMA mode 0
30ns
16
480ns
(1/480ns) x 2byte = 4.16MB/s
DMA mode 1
30ns
5
150ns
(1/150ns) x 2byte = 13.3MB/s
DMA mode 2
30ns
4
120ns
(1/120ns) x 2byte = 16.6MB/s
DMA/33
30ns
4
120ns
(1/120ns) x 2byte x2 = 33MB/s
