Philips DVDRW22899 User Manual page 20

the IDE cables. But sometimes it is possible to disable this BIOS search for individual internal drive
positions.
So always check whether your BIOS allows detection of a newly connected internal drive (e.g. a new
CD-ReWriter or DVD+RW drive), otherwise the Windows operating system will probably not be able to
use this drive.
For checking and/or changing your BIOS settings, watch closely for any texts appearing on your
screen during start-up of your computer. You will have to press the key mentioned on the screen (e.g.
F2, Delete, Esc, etc.) to go to the BIOS settings menu. Then find the drive detection settings and make
sure they are all set to "AUTO DETECT" so that any newly connected drive will be enabled by your
computer's BIOS.
DMA vs. PIO mode
Traditionally, CD-ROM drives have used Programmable Input Output (PIO) rather than Direct Memory
Access (DMA) for data transfer. This was favored for the earlier designs because hardware
implementation is simpler and is adequate for devices requiring low transfer rates. The drawback is
that the CPU must mediate the transfer of data, often byte by byte. As the data rate of CD-ROM drives
has risen, so has the load on the CPU, to the point where 24-speed and 32-speed drives can
completely saturate CPU utilization in PIO mode.
DMA data transfer is always more efficient and requires only a few per cent of CPU time. It uses
hardware to control data transfer directly to system memory, and requires only initial memory
allocation and minimal handshaking from the CPU. A further advantage is that performance is device-
rather than system-dependent. DMA-capable devices should give consistent performance, regardless
of the system to which they are attached.
DMA has only recently been common for IDE devices and interfaces, and only the Windows 95 OSR2
service release and higher Windows versions have included DMA drivers for the Intel PIIX range of
IDE/PCI bridge chips. But DMA is often not enabled in systems equipped with these operating system
versions,either due to ignorance or from concerns about overall system stability.
The CD-ReWriter Setup program automatically assigns DMA control for the drive if possible on the
system.
Firmware upgrades
The embedded software in the drive itself can also be updated with newer software versions. Go to the
Philips Support web site for downloading the necessary software tools and firmware updates. See
Downloads for more information.
See http://www.pctechguide.com/search.htm for an explanation of any terms in the text above.