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Warp 4 tuning tips

It's sad but true ... the installation defaults for OS/2 are set up to emphasize a glossy appearance rather than performance. By changing various parts of the system configuration, you can get a much speedier system.

Also available in Japanese thanks to Toda Haruo.

See also

Recent changes

The information on this page is aimed at users of OS/2 Warp 4; but it comes from experience with all versions of OS/2 since version 2.0, so a lot of it is not version-specific. Most of the tips are not original with me, they came from various net.helpers. Unfortunately I didn't think to keep track of their names, so I'll have to confine my acknowledgments to a big thanks to the entire OS/2 community out there.

The programs mentioned here are available from the usual OS/2 archive sites. See my list of recommended freeware for more details.

Some useful tools

Changes that everyone needs

Speeding up desktop operations

Disk drivers

Most of the items in this section apply only to those people who have IBM1S506.ADD in their CONFIG.SYS. This is the driver for IDE and similar drives. I'd love to have something similar for SCSI drives, but so far I don't have much good advice for SCSI users. There's just one note at the end of this section that applies to SCSI drives. Here's an example of a CONFIG.SYS line where both these options are turned off, for a hardware configuration where there's a single disk adapter (controller number 0) that is controlling two hard drives (unit 0 and unit 1).
   BASEDEV=IBM1S506.ADD /A:0 /!BM /U:0 /!SMS /U:1 /!SMS
Note that you must specify which adapter and which unit(s) you want the options to apply to. For further details type HELP IBM1S506. You might need to experiment a little to work out whether it's better to enable or disable either of these features, it probably depends on your precise hardware configuration.

Remark: My own experience tends to suggests that there's some deeper problem here: something in the file system is effectively preventing multitasking which a disk operation is in progress. The above measures reduce the impact of the problem but don't really get at the root cause, which is (I believe) some sort of design error inside OS/2.

My reason for believing this is that the WPS also goes "dead" when a SCSI operation is in progress, or when you copy a file to or from a floppy disk. (This last case is particularly noticeable.) This did not happen in Warp 3 - there's something new in Warp 4 that makes the file system a processor hog.

Leonard Pennock ( has done some tests, on an HPFS/SCSI system, that tend to suggest that the slowdowns can be cured by turning off lazy writes. This didn't give any improvement on my system; but it's something you can easily try on your own system, to see whether it makes a difference. (The appropriate command is "CACHE -Lazy:OFF". You don't have to re-boot to do this.) If it does help, it could mean that there is a bug in the implementation of HPFS lazy writing. I'd be interested to get feedback on whether this works for other people.

Internet applications

Windows applications

The WarpCenter

To change WarpCenter features, use a right mouse click on the WarpCenter object in the OS/2 System folder, and choose Properties.

Deregistering unwanted classes

The concept of a "registered class" is fairly vital to the way OS/2 works, and most registered classes should stay registered. Unfortunately some such classes seem to slow the system down a fair bit, so it's worth getting rid of the ones you'll never use.

There are several alternative tools for deregistration. The one I recommend may be found in the archives as wpsutil/

Removing unnecessary files

Normally I don't physically delete unneeded files, in case I should change my mind later. (If you do delete any, keep track of which ones they were, so that you can restore them from CD-ROM if necessary.) Regardless of whether you keep these files, it's worth cleaning the rubbish out of CONFIG.SYS.


Dealing with a noisy phone line

This topic has generated so much discussion that it deserves a section of its own. This section will interest you if you use a modem, and you get a lot of "[NETW] Invalid FCS" error messages.

Any phone line has a certain amount of line noise, so you can expect an error like this now and then. (The software requests a retransmission when it detects the error, so you haven't lost anything except a bit of speed.) But if you're getting many such errors, you have a problem - especially when the connection degenerates to a "lost carrier" condition, at which point you've lost your connection.

There are actually several likely causes of modem data corruption:

Unfortunately the symptoms of all these problems are similar, so it can be hard to pin down exactly why you're having trouble. The tips below might or might not help you; all I can suggest is that you try them one at a time, to see which (if any) change gives an improvement.

Other sites with tuning and setup tips

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This information was compiled by Peter Moylan. Please send complaints, criticisms, praise, corrections, suggestions, etc. to peter at
Last modified: 23 July 2004