User`s guide

Frequently Asked Questions
B-5
A: The traditional PIO (Programmable I/O) IDE requires the CPU to involve in
all the activities of the IDE access including waiting for the mechanical
events. To reduce the workload of the CPU, the bus master IDE device
transfers data from/to memory without interrupting CPU, and releases CPU
to operate concurrently while data is transferring between memory and IDE
device. You need the bus master IDE driver and the bus master IDE HDD to
support bus master IDE mode. Note that it is different with master/slave
mode of the IDE device connection. For more details, refer to section 2.3
"Connectors".
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
Q: What is the performance of Ultra DMA/33? Do we need special driver?
A: You need driver to activate DMA/33, there are now driver from INTEL or you
can use driver in the Windows 95 Memphis, which can recognize South
Bridge PIIX4.
We got the mass production sample Quantum Fireball ST1.6A, following are
the test result.