Chapter 13: System Resources^307
Ultra DMA
PIO data transfers are no longer used on newer systems, having been replaced by DMA
and more recently, Ultra DMA (UDMA), which supports data transfers between a device
and RAM of up to 100 MBps. Most of today’s PCs support at least UDMA/33 (33 MBps
transfers) and many support UDMA/66. UDMA mode 5, the newest version, supports
data transfers of 100 MBps and is known as UDMA/100 and Ultra ATA/100.DMA versus UDMA
Understand that UDMA is a transfer mode that is used almost exclusively by ATA (AT
Attachment) and ATAPI (ATA Packet Interface) devices, like hard disk drives,
CD-ROMs, or DVDs. UDMA is not normally considered a system resource and was in-
cluded primarily to contrast it to DMA, which is a system resource that is assigned to and
used by many devices.Resolving Resource Conflicts
As has been mentioned more than once in this chapter, the Windows Device Manager is a
good place to start when you think you may have a system resource conflict. How do you
know you have such a conflict? Typically, if you’ve installed a new device and any of the
following symptoms show up, you most likely have a resource conflict: The PC locks up frequently for no apparent reason.
The mouse operates erratically or not at all.
The PC boots into Windows Safe Mode.
You cannot format a floppy disk in the floppy disk drive.
Anything printed on the printer is gibberish.
The monitor displays distorted or strange images.
The sound card either doesn’t work or doesn’t sound just right.
Any existing device that was working before suddenly stops working.
You have updated your antivirus program and scanned the PC, so a virus is
not causing the problem.Once you’ve determined you might have a system resource conflict, look at the De-
vice Manager to see if any of the installed devices have one of the three get-your-attention
symbols: the bluei, the redX, or the yellow exclamation point. If they do, determine if it
may be related to the problem. It isn’t always easy to tell if a particular device is causing
problems with another; if a device has a red or yellow symbol, your best bet is to resolve
that issue before proceeding.