CDRW: cdrecord: No disk / Wrong disk!

[Lennart Sorensen]

On Fri, Jul 14, 2006 at 06:28:45PM -0400, Zbigniew Koziol wrote:
> I never thought there is such  a thing as firmware update for CD drive ;) OK, 
> I did the homework. There is just one, it seems, firmware update available 
> for this particular drive but it is related to its reading capabilities of 
> DVD.

For DVD writers firmware updates are a big deal to support new media as
it comes out.  That is why I tend to buy plextor drives (well that and
they are just great drives if you buy their high end models), since you
can flash the firmware from linux on a plextor.

> Thats an educative information in my case. But I did try several CDs, from 
> various manufactures, and got also a pair of two for free from the store I 
> bought the drive.
> 
> I guess I will end up buying another CD recorder ;)

Well you can pick up a pioneer or LG dvd burner for about $40.  A
plextor will be closer to $125.

> What is the role of DMA during the recording? One of tools I used on Linux 
> throws out a message that there is no DMA at all. Is that important? That 
> particular CD drive works as a secondary master.

The author of cdrecord to put it mildly is a bit nuts.  He hates how the
linux kernel developers have decided to handle atapi and prints out lots
of warningsa (which only apply to a few specific kernel releases) on just
about every kernel version.  DMA is important for decent recording speed
(I wondered why a DVD was taking 2 hours to burn on my machine, when
something accidentally disabled DMA.  With DMA enabled it took 15
minutes instead.)  Without DMA the cpu has to copy every byte to the
device, while with DMA the cpu just places the data in ram, and tells
the device the address in ram to go get the data, and the
device/controller takes care of getting the data there while the cpu
goes and does something useful instead.  This is much faster and much
more efficient.

To check if DMA is enabled do:
cat /proc/ide/hdc/settings|grep dma (where hdc is your writer).  

If you see using_dma 1 0 1, then it is enabled, while 0 0 1 means
disabled.  You can enable it with 'hdparm -d 1 /dev/hdc' assuming you are
running a native driver for your ide controller, and not ide-generic.
Some kernels enable DMA all the time, some only do it for harddisks,
and some don't do it at all.  You can make it run the hdparm command at
boot from one of the startup scripts.

Without DMA burns are much more likely to fail if you don't have buffer
underrun protection enabled (cdrecord disables it by default, while
cdrdao, and growisofs and most other things enable it by default).

--
Len Sorensen
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