Re: cdrecord: DMA speed too slow

[scdbackup@gmx.net]

I found a way to slow down my writer drive (hdc) by simultaneously using
my DVD-ROM (hdd). That produces DMA speed measurements of about 1500
to 2500 kB/s. 

cdrtools-2.01a35 reports :

  Drive DMA Speed: 1435 kB/s 8x CD 1x DVD
  ...
  cdrecord: DMA speed too slow (OK for 8x). Cannot write at speed 10x.
  Starting to write CD/DVD at speed 10 in real TAO mode for single session.

After a few minutes i stopped the reading process at hdd and cdrecord began
to report speeds of 10.1x to 10.6x. Average speed was ~ 7x.

Blanking without driveropts=burnfree worked fine despite this measurement :
  Drive DMA Speed: 1428 kB/s 8x CD 1x DVD
Thanks, Joerg. (I'll try to read more AN.*)

Quite funny, nevertheless, is this message :

  Drive DMA Speed: 2429 kB/s 13x CD 1x DVD
  ...
  cdrecord: DMA speed too slow (OK for 13x). Cannot write at speed 10x.
  Starting to write CD/DVD at speed 10 in real TAO mode for single session.

cdrecord was started with speed=10 . Why does it complain about speed 13x ?

Now i kept the reading process alive during the whole burn of 589 MB.
cdrecord reported speeds of 2.2x until suddenly it went up to 10.3x or 10.9
after half of the CD was done. The DVD-ROM was busy all the time.
After about 50 MB cdrecord slowed down to 2.0x again. Average speed was ~ 3x.

I never saw a prediction below 8x during my tests whereas the reported
writing speed is quite enduringly near 2x when hampered by the DVD-ROM.

Despite "Total of 27 possible drive buffer underruns predicted." the
CD was readable. (It is a "4x-12x" media which does not work with 2x writers
and even not with some 4x writers. My DVD writer refuses to use old 2x CD-RW.
But with "4x-12x" CD-RW it writes speed 2x.)


Have a nice day :)

Thomas