User Guide

Frequently Asked Questions
B-6
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.
MB : AOpen AP5T
CPU : P54C-200 Mhz
DRAM : 16MB * 2 (FP-7)
VGA : AOpen PV60
CDROM : AOpen CD-920E (20X)
OS : Win95 OSR2