ON TEST BURN-PROOF CD WRITERS
Burn-proof technology
FIREBREAK
CHRISTIAN REISER
Most burn interruptions are due to buffer seconds. The burner software forms a buffer in the
underruns. A buffer underrun occurs when the memory, meaning that, in burner software such as
computer fails to transport data fast enough to the cdrecord, buffer allocation is up to you. The
CD burner. This means that the internal buffer standard size is 4MB.
memory of the CD burner is empty, thereby The latest method for avoiding buffer underrun,
rendering the CD-ROM incomplete and unusable. BURN-Proof, stands for Buffer Under RuN and
The reason for this is that the data has to be comes from Sanyo (http://www.sannet.ne.jp/ BURN-
Even in these days
written onto the CD at a constant rate. It is Proof/). BURN-Proof takes the innovative approach
of gigahertz CPUs,
therefore crucial that both the speed of CD of attempting to prevent not the underruns
rotation and the laser path across the surface of themselves, but their consequences.
CD burning often means
the disc are kept at a regular rate. The inner tracks A small microcontroller inside the CD burner
burnout. But you can
are shorter, the outer ones longer. In order to run constantly clocks the fill level of the built-in buffer. If
at the required constant rate, the CD-ROM must it detects a risk of buffer underrun (where the
blank out memories
run faster when reading the inner tracks than it buffer is less than 10% full), it initiates the ending
of meltdown with
does when reading the outer ones. Consequently, of the burn procedure. If the data has been written
CLV (Constant Linear Velocity) ensures that the onto the CD-R, the chip remembers its location. As
BURN-Proof technology.
laser always covers the same distance per unit of soon as the buffer is full again, the CD burning
time. software restarts the burn procedure. This means
In the case of single-speed devices, the data rate that this software must also support BURN-Proof.
is 2352 x 75, giving a speed of 176,400 bytes per The microcontroller recommences burning at the
second. A burner with 12x acceleration point at which the last data was burned.
consequently writes at 12 x 176,400 bytes per Similar software from Ricoh and Yamaha are
second a speed of just over 2MB per second. This called JustLink and Waste-Proof Strategy
quantity of data has to be supplied constantly by respectively. So far however, only BURN-Proof has
the computer. Until now, incremental burning was made it onto the market. Linux supports this
not an option. technology with cdrecord and cdrdao from version
1.1.5 onwards.
Buffer solution
Using BURN-Proof
Several procedures have been developed to
circumvent this well-known problem. The first You can determine whether a drive supports
solution developed was to incorporate the buffer BURN-Proof by using the command
into the burner itself. The newer burners hold
# cdrecord -checkdrive dev=0,X,0 driveropts=U
buffer capacities of up to 4MB, meaning that a
help
maximum burn rate lasts for about 1.5 to 2
Cdrecord 1.10a16 (i586-pc-linux-gnu)U
Copyright (C) 1995-2001 Jrg Schilling
[...]
Driver options:
How we tested
burnproof Prepare writer to use SanyoU
BURN-Proof technology
Tests were performed on an AMD K6-2 at 350 MHz and with kernel 2.4.2. In
noburnproof Disable using Sanyo BURN-U
the CD-R tests a 691 MB ISO-9660-Image was burnt onto the CD-R. In the
Proof technology
CD-RW tests we settled for 137MB. The read tests always went via the inner
tracks the first 100MB and the first 10 minutes of the test CD.
The X can be defined via cdrecord -scanbus. An
example can be found in the IDE/ATAPI burner
42 LINUX MAGAZINE 10 2001
BURN-PROOF CD WRITERS ON TEST
CD burners with buffer-underrun protection
Manufacturer Lite-On Plextor Plextor Plextor Ricoh Teac
Website www.liteonit.com.tw www.plextor.be www.plextor.be www.plextor.be www.ricoh.de www.teac.de
Model LTR-12101B PX-W1210A PX-W1210S PX-W1610A MP9120A-DP W512E
Shop price Ł115 Ł150 Ł225 Ł170 Ł175 Ł120
Speed (Write/Rewrite/Read) 12/10/32 12/10/32 12/10/32 16/10/40 12/10/32(/8 DVD) 12/10/32
Connection ATAPI ATAPI SCSI ATAPI ATAPI ATAPI
Buffer-underrun protection BURN-Proof BURN-Proof BURN-Proof BURN-Proof JustLink BURN-Proof
Speed test:
Burn CDR [kB/s] 1750 1736 1747 2265 1761 1739
Fix CDR [s] 25.3 24.2 24.6 18.9 22.9 27.9
Burn CDRW [kB/s] 1212 1278 1272 1107 1406 1302
Fix CDRW [s] 28.0 33.8 34.1 33.7 35.4 34.4
Read CD-ROM [kB/s] 2145 2479 2512 3094 2483 2414
Read audio (playing time/read time) 2.27 5.45 6.06 5.22 1.86 3.05
under Linux box. BURN-Proof is activated with the and starting other tasks. In the end we managed to
addition of the parameter driveropts=burn-proof to fabricate a buffer underrun on all the drives and
the normal cdrecord command. BURN-Proof always caught them, although
cdrecord does not issue a message when this
happens.
But does it work?
Now to reality: We had five drives using BURN-
Conclusion
Proof and one drive using JustLink in our test.
Although employing the same approach to buffer All burners with BURN-Proof function perfectly,
underrun as BURN-Proof, JustLink has to be started the interruption of the flow of data has no effect on
up differently; cdrecord cannot do it. We did not the legibility of the CDs. But Sanyo states that CDs
experience this problem with either SCSI or with produced using BURN-Proof should preferably be
ATAPI. But it was considerably harder than expected read with a 4x CD-ROM or a CD-player built after
to test the CD burners on BURN-Proof. Since 1995. Every interruption in the write process results
cdrecord uses the POSIX real-time expansion, it has in a small gap, which could in some circumstances hdX: Under Linux, all
a higher priority than all other tasks; only the kernel cause older drives to get out of step. Only the Ricoh IDE devices are addressed
takes precedence. This is no place to start. There is drive produced illegible blanks in the test. JustLink is as /dev/hdX. hdX in this
no point in blocking the IDE bus in order to slow the not currently supported by any Linux burn program. case stands for: hda: first
progress of data to the burner, since no modern IDE If you are buying one, check whether cdrecord or controller, master hdb:
device is capable of overtaxing the IDE bus cdrdao can cope with the respective burner. first controller, slave
permanently. The only remaining option is to slow Considering today s high-performance hdc: second controller,
down the data to be burnt before it gets to computers however, a question naturally presents master hdd: second
cdrecord. We created the data on the fly (without itself: Do we really need a device with this controller, slave.
dumping it on the hard disk) with mkisofs and technology? Burnt CDs are something of a rarity
brought this task to a stop by lowering its priority at least under Linux. %
IDE/ATAPI burner under Linux
cdrecord directly supports SCSI burners, assuming correct installation of the SCSI-Host adapter. ATAPI devices must first be
converted from IDE to SCSI-API. This is conducted via the kernel module ide-scsi: This module provides a SCSI emulation for
every IDE drive which is not yet occupied by another driver, so that it appears to programs as a genuine SCSI drive. The real
problem now is to keep the CD burner free for the IDE-SCSI module. Here the methods differ depending on whether the IDE
CD-ROM is permanently supported in the kernel, or if it is loaded as a module (IDE-CD). The simplest way to find this out is by
mounting a data CD into the file system and then using lsmod to check if the IDE-CD module has been loaded. If the IDE-CD
support is firmly anchored in the kernel, this means you have to tell the kernel by boot parameter that it should keep the
burner free for the SCSI emulation. This is done using the parameter hdX=ide-scsi. From now on, /dev/hdX is no longer
available and the burner can be addressed via /dev/scd0. The boot parameter should be permanently entered in the
bootloader; in the case of LILO, the append entry in the /etc/lilo.conf is extended to do this:
10 2001 LINUX MAGAZINE 43
ON TEST BURN-PROOF CD WRITERS
append = hdX=ide-scsi
If parameters already exist under append, hdX=ide-scsi is placed before them and separated from the rest by a comma.
If ide-cd is not fixed in the kernel, then the ide-cd parameters must be adapted first so that this module no longer accesses the
burner. Secondly, the ide-scsi parameter must be altered so that other devices are not occupied, even when their driver has
not yet been loaded. Both settings are defined in the file /etc/modules.conf. For the ide-cd-module, just the line
options ide-cd ignore=hdX
needs to be inserted. Making sure that ide-scsi only occupies the burner is unfortunately not that simple there are no
options for modules. For this reason, you need to make sure that all drivers for any other possible devices are already loaded
before the ide-scsi module is initialised. This is effected by the following entry:
pre-install ide-scsi modprobe -k ide-cd;modprobe -k ide-tape;modprobe -k ide-floppy
The parameter -k ensures that the drivers are unloaded automatically when they are not needed.
Last of all, in both cases the ide-scsi emulation must be entered as SCSI controller:
alias scsi_hostadapter ide-scsi
Whether everything has worked is shown by
# cdrecord -scanbus
Linux sg driver version: 3.1.17
Cdrecord 1.10a16 (i586-pc-linux-gnu) Copyright (C) 1995-2001 Jrg Schilling
Using libscg version schily-0.4
scsibus0: 0,0,0 0) TEAC CD-W512EB 2.0B Removable CD-ROM
0,1,0 1) *
0,2,0 2) *
0,3,0 3) *
0,4,0 4) *
0,5,0 5) *
0,6,0 6) *
0,7,0 7) *
44 LINUX MAGAZINE 10 2001
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