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Troubleshooting
2. Some overruns are caused by SMARTDRV write caching. To dis-
able write caching but continue read caching, specify the drive letter
without a + or -. For example, SMARTDRV C enables read caching
but disables write caching. Note, however, that this will slow the PC
down.
3. Remove the DOS=HIGH statement from CONFIG.SYS as it causes
interrupts to be delayed longer. Note that this will take up precious
CONVENTIONAL memory space.
4. An ill-behaved TSR may be contributing to the problem. If so, try to
isolate it by removing all TSRs then adding them back one at a time.
5. Run in standard mode. Windows stops virtualizing I/O and there is
less overhead.
6. Remove the SOUNDS.DRV driver (which enables a variety of
sounds from your PC speaker) if it is present, as this disables inter-
rupts while activated.
Other things you could try are listed below.
● Check that you are using the Windows versions of EMM386,
HIMEM.SYS and SMARTDRV, and not the DOS versions.
● Don't run multiple disk-caching programs.
● In CONFIG.SYS, set FILES to 30 or higher.
● Check that you have SHELL=COMMAND.COM / E:2048 /P i.e.
2K environment.
● If Windows hangs, increase the stacks to 64,512. The recommenda-
tion is 0,0.
● Check that your TEMP variable points to a subdirectory that actually
exists and that there are at least 2 megabytes free on the disk.
● Check that EMMExclude=A000-EFFF, otherwise Windows will
interfere with (DOS) high memory when it shouldn't.
● For bizarre problems, disable shadow RAM. If this rectifies the prob-
lem, upgrade your BIOS.
● Disable hardware cache in caching disk controller.
● If you are using V3.1 of Windows communication drivers then try
using a serial port with a 16550 UART.
Note: Microsoft has produced a document called CE_OVERRUN
Errors with Serial Communications which can be obtained
by contacting Microsoft and asking for document number
Q79988.