Using Ultra DMA with my CD-ROM drive

  • Thread starter Thread starter Ameer K.
  • Start date Start date
A

Ameer K.

I have a 44x cd-rom drive thats using UDMA 2 on the
secondary master. Earlier today I added an old cd burner
to my computer that uses UDMA 1 as the secondary slave. I
have read that using devices with different UDMA speeds
on the same channel will cause both devices to operate at
the lower speed, is this true? Will my CD-ROM drive now
operate at UDMA 1? thanks.
 
You do not need to worry about it as you can't even reach the full speed
of DMA Mode 1 with a CD-ROM drive. DMA Mode 1 provides 25 MB/s whereas
your 44x CD-ROM drive's max throughput is 6,600 KB/s or about 6 MB/s.
It will run both in DMA Mode 1, but you don't need to worry about that
at all unless you are hooking up a DVD Drive to it.
 
The ability of IDE/ATA channel to operate a master and slave device using
different transfer modes is called independent device timing. The hard disk
controllers integrated on modern chipsets all pretty much support
independent timing, as do modern add-in controllers, but this was not always
the case. Independent timing can be an issue if, for example, you upgrade an
older PC and get a new, high-speed drive, but want to continue to be able to
use the older one on the same channel with the new one.

There are several reasons why optical drives (or other ATAPI devices) should
not be shared on the same channel as a fast hard disk. ATAPI allows the use
of the same physical channels as IDE/ATA, but it is not the same protocol;
ATAPI uses a much more complicated command structure. Opticals are also
generally much slower devices than hard disks, so they can slow a hard disk
down when sharing a channel. Finally, some ATAPI devices cannot deal with
DMA bus mastering drivers, and will cause a problem if you try to enable bus
mastering for a hard disk on a channel they are using.
 
Uhm, such twisted logic might lead to imagination we don't need anything
better than i386 computer :o) For instance, internal sustained transfer rate
of any hard disk is much less than external STR and far below 66MB/s. The
only advantage of the fast IDE interface is that IDE device can release the
bus earlier.
 
Ameer said:
I have a 44x cd-rom drive thats using UDMA 2 on the
secondary master. Earlier today I added an old cd burner
to my computer that uses UDMA 1 as the secondary slave. I
have read that using devices with different UDMA speeds
on the same channel will cause both devices to operate at
the lower speed, is this true?
Click to expand...

No it isn't. On any half way modern motherboard and controller they are
handled independently
 
-----Original Message-----
I have a 44x cd-rom drive thats using UDMA 2 on the
secondary master. Earlier today I added an old cd burner
to my computer that uses UDMA 1 as the secondary slave. I
have read that using devices with different UDMA speeds
on the same channel will cause both devices to operate at
the lower speed, is this true? Will my CD-ROM drive now
operate at UDMA 1? thanks.
.
Yes, I'm afraid that it is true but only if you have
Click to expand...
both devices on the same controller. Both cd-rom's will
run at UDMA 1 if used on the same controller/cable. Good
news though, within the last couple of weeks there have
been a few DVD recorders released that run SATA.
 
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