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by Alistair Mackay >> Tue, 16 Nov 1999 3:30:30 GMT

I have an application which accesses documents on a CD-ROM. It is fine with Windows NT, but very slow on Win 95. Can you help?

by Skull >> Tue, 16 Nov 1999 9:12:05 GMT

Alistair,

Firstly, some questions:

1) Is this a JADE app? If so what facility are you using to access the documents, the JADE File class or something else?
2) Is your document access typically sequential or random in nature?
3) Do all applications exhibit slower performance using the CD-ROM from win95 or just this particular app. Try comparing the elapsed time to copy files from the CD-ROM to Hard disk between win 95 and NT, allthough this test may not provide a true reflection of performance variations for random access.
4) When accessing your documents under win95 does the CD spindown or start/stop more often than under NT? Compare the behaviour of the inuse light between the two.
5) Just for the record what is the CDROM brand, model, speed and interface (IDE or SCSI)?

Here are some things to try or check under win 95:
1) Ensure that you don't have a legacy real-mode device drivers installed for the CDROM. To check this go from the My Computer - properties - performance tab. This should read 'Your system is configured for optimal performance', if you have real-mode CDROM drivers installed it will say so here, and if you do remove them!
2) While still on the System Properties performance tab, click File system and select the CDROM tab, from there ensure that 'Supplemental Cache Size is set to large and 'Optimize access pattern' is set to the highest speed shown in the listbox.

By the way if your drive is E-IDE or Atapi with DMA (Direct Memory Access) support you can achieve performance improvements in both Win 9x and NT by enabling DMA. In particular DMA dramatically reduces the CPU utilisation required to transfer data. You will probably find that DMA is not enabled by default in win 95, or NT 4 (it should be in Win 2000 if the hardware supports it).