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This page is a result of my own research. I made one after very strange article in one ukranian computer magazine. For this research I wrote tree applications: for Windows 95/NT, MS-DOS and UNIX. You can download it here. These applications read CD-ROM sector by sector and measure reading time. Applications allow save measurement results in file and you can plot reading speed graphics using program like Microcal Origin. Windows application is a GUI program, you can see it window below.
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CDSpeed32 have separate function for Windows 95 and Windows NT written correspondently Microsoft documents Q137813.txt and Q138434.txt.
My friend Alex Filippov, using my DLL, wrote similar more facilities program "CDRom Drive Analyser". First version was written on Visual Basic 5.0 and require VB DLL and OCX, but version 2.0 rewritten and work properly itself.
Experiment was made on Pentium 200MHz with 32MB RAM with two 24x IDE CD-ROM: Teac CD-524 and Creative CD-2423. You can see results below. Besides Windows 95, NT and MS-DOS, I test UNIX FreeBSD 2.2.5 and Sun Solaris 2.6 for x86 (2 processors Pentium 2 260MHz 128MB RAM, Teac CD-524 only, block interface). As you know UNIX system have two means access to disk: character and block. In first case data is read directly to process address space, but in second case kernel reads data in own memory and next copies data to process address space. Therefore, first interface must be more performance than second.
Modern CD-ROM drives have continuous rotation speed and, therefore, reading speed must linear grows from begin of disk to end of one.Well, look at the picture below!
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You can see that Windows NT 4.0 perfectly copes with a task, but Windows 95 (4.00.950 ), MS-DOS and FreeBSD (from block interface-usually using interface) have growing speed only on short piece of disk and long "tableland" on certain speed. This speed may be in two times less then manufactory speed! For my request my friend tested 32x Teac CD-532 on Pentium 188MHz, 64MB RAM under Windows 95/98/NT and MS-DOS. See results below...
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I made similar research for hard disks. When I setup DMA driver bmide_95 , I test my CD-ROM again and obtain results which you can see below.
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This page has existed more than one year without changes, but I can't understand "Why Windows 9x doesn't use all speed possibilities of modern CD-ROM drives". Microsoft documents recommend to use for CD-ROM sector access old MS-DOS fashion MSCDEX interface. Probably this interface limit reading speed? I wanted to write similar test program which used ASPI interface for sector access, but I had not time. At last I knew, that such program exit, it is CDSpeed99. Speed test result obtained with this program looks more optimistic, but I had only one last question: which interface use Windows 9x itself (I hoped that ASPI, but I wanted to know more definitively)? I have write a program CDSpeed32Ex, this program read the file and measurement reading speed and wrote to CD one file with size 650MB, therefore this file was the same that CD, it was a image of all CD-ROM sectors. You can see results below:
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Definitively that Windows 9x use ASPI interface for CD-ROM access and my old results are very doubtful!
“You never make mistake, if you do nothing” :-).
visitor on this page.All contents copyright © Victor M. Grinenko, Ver 1.00 October 8, 1998. changed May 27, 2000