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-
- CD-BENCH v2.0
-
-
- Many people think that the data transfer rate of CD-ROM drives
- is constant from the beginning to the end of the disc, but this is
- true only for old-and-slow models, the so-called CLV (Constant
- Linear Velocity) drives. High speed drives use the CAV (Constant
- Angular Velocity) technology or the mixed CLV/CAV one. The speed
- of CAV drives grows continuosly from the beginning to the end of
- the disc while in CLV/CAV drives it rises quickly up to the maximum
- and then remains constant.
-
- Many common benchmarks report a completely wrong result because
- they suppose that the reading speed is constant, so they read only
- at the beginning of the disc. CD-BENCH, instead, is the only
- benchmark that reads the disc in six different points and displays
- six results, so you can see if and how the speed varies.
- To perform a complete test (six readings), you need a CD
- containing at least 301500 sectors (589 MB). Note that CAV drives
- reach the maximum speed only towards the end of the disc (of a
- *full* disc) so you should use the fullest disc you have.
- If you use the -S switch, CD-BENCH reports the size of the
- inserted disc without performing any test. Note that many DOS
- programs (including Microsoft DosShell) report a wrong size.
- By the -D switch you can change the delay that precedes each
- reading. During this time the drive's read-ahead buffer (an
- internal cache memory) is filled with the data that CD-BENCH is
- going to read. The default is -D=500 (500 milliseconds), it should
- be enough to let your drive perform well. With -D=0 the drive is
- tested in the worst case.
- By the -B switch you can change the quantity of data that
- CD-BENCH reads. High values reduce the influence of drive's
- internal cache so giving worse results; in other words you can use
- this switch to modulate the influence of caching on results. The
- default is -B=15 (1500 sectors).
-
- CD-BENCH also measures the average access time by performing 100
- random accesses to sectors located in the first 300 MB of the disc.
- Using a fixed portion of the disc ensures that the result depends
- only on the drive speed and not on the disc size. If the disc
- contains less than 300 MB of data, CD-BENCH skips this test.
- The sequence of 100 accesses is only apparently random: it is
- always the same, every time you perform the test; in this way,
- again, the result depends only on the drive speed.
-
- You can effect only the first test (data transfer rate
- evaluation) or only the second one (access time evaluation) by the
- -1 and -2 switches.
-
- CD-BENCH can also be used to verify whether a disc is defective
- (that is whether it causes read errors or not): by the -A switch,
- in fact, you get CD-BENCH to read the whole disc. Of course
- this task takes several minutes.
- IMPORTANT NOTE. Many drivers have a little bug that causes
- CD-BENCH to read farther the end of the disc so generating a read
- error. This problem takes its origin from a wrong formula in a
- Microsoft's official document; a more recent version of that
- document is correct but many drivers are still buggy (this includes
- Windows 95's internal driver!).
-
- CD-BENCH interacts with the 8253 timer chip to get high
- resolution timing (0.1 ms) and, therefore, highly accurate results.
-
- The presence of a disk cache like SMARTDrive can lead to
- unrealistic results. CD-BENCH temporarily disables SMARTDrive
- v4.0+ or compatible caches (PC-Cache v8.0+ and the most recent
- versions of Norton Cache are known to be compatible) and restores
- their original status before returning to DOS, even if you abort
- the program by pressing Ctrl-Break or ejecting the disc (I don't
- lock them so you are free to do as you like).
-
- If no parameter is supplied on the command line, CD-BENCH tests
- all the available CD-ROM drives; if you want to test only one of
- them, just specify its letter.
- IMPORTANT NOTE. If you didn't install both MSCDEX.EXE and a
- proper device driver for your CD-ROM drive, CD-BENCH can't see the
- drive and displays the message "No CD-ROM drive found".
-
- CD-BENCH cannot run as a DOS task of Windows 95 or OS/2: you
- have to use "plain" DOS.
-
-
- --=<>=--
-
-
- How to get good results.
-
- 1) Use a clean, unscratched, "silver" disc. CD-Recordable weakly
- reflect the laser beam so they are harder to read. When a read
- error occurs the drive repeats the read operation twice or more
- times and can also reduce the spin (some models only). Of course
- this behaviour influences negatively the result.
-
- 2) Some discs are unbalanced and cause strong vibrations when they
- rotate at high speed. Some drives detect these vibrations and
- reduce the spin, so, if the first run doesn't give good results,
- try to use another disc. BTW: never attach labels on CD-ROMs!
-
- 3) Visit the web site of your drive's manufacturer and check
- whether a new version of the driver is available.
-
- 4) Some old BIOS is programmed in the way that it recognizes any
- CD-ROM drive as a "PIO Mode 0" device. This is not a good thing if
- you have a very fast drive (20x or more) because PIO mode 0
- actually holds your drive back. If this is your case, you should
- contact your mainboard vendor for a BIOS upgrade so that your high
- speed drive will be recognized as a PIO mode 4 device.
-
-
- --=<>=--
-
-
- I thank the persons that have tested a pre-release of this
- program on drives different from my one so giving me a general
- survey of the market. They are Andrea Campagnolo, Adriano Cata-
- pano, Giacomo Cocchella, Vittorio Colosio, Alessandro Del Rosso,
- Andrea Galli, Allan Jong, Patrick Lee, Gaetano Petronzio, Alessan-
- dro Queri, Cicci Serra.
-
- CD-BENCH is a copyrighted free program. It can be freely used
- and distributed but cannot be bundled with hardware products
- (drives, CD recorders, etc.) without my written permission.
-
- Your feedback is welcome.
-
-
- My addresses are:
-
- E-mail: pnavato@poboxes.com
- pnavato@geocities.com
- Pino Navato, 2:335/225.18 (The Bits BBS, Fidonet)
-
- WWW: www.poboxes.com/pnavato
- (currently forwards to
- www.geocities.com/SiliconValley/4421)
-
- Mail: Pino Navato
- Via Pittore, 164
- 80046 S.Giorgio a Cremano (NA)
- ITALY
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