ERRORMSG: Overrun error detected during download

Article ID: 010307sab
Last Reviewed: July 10, 2023

The information in this article applies to:


Pronto for Windows produces the error message during download:

Overrun error: Character received, but not processed before the next character arrived.


This problem is caused by the Windows serial driver failing to collect a character from the serial port before another one arrives and overwrites it, causing it to be lost.


On Windows 95/98 and ME, Windows 2000/XP
A solution is as follows:

  • open MY COMPUTER
  • open SYSTEM
  • click on DEVICE MANAGER tab
  • select PORTS
  • select the COM port that is being used
  • click on PROPERTIES
  • click on PORT SETTINGS tab
  • click on ADVANCED
  • Reduce the setting for the Receive Buffer (move it to the left).
  • click on OK
  • click on OK

Typically it is only necessary to move the setting one division to the left but some device drivers may ‘hog’ the processor requiring further reduction. Using a lower setting reduces processor performance very slightly (a couple of percent). Note that changes made to this setting only take effect after a reboot. On Windows NT4 the receive buffer setting can only be changed using the registry editor, this setting is stored under the key:


In the value:


In Windows NT4 the default is 8, change this setting to 4 or 1 to reduce the incidence of overrun errors. Note that changes made to this setting only take effect after a reboot.

NOTE also:

On Windows 3.1 and on some old computers (particularly 486 and early Pentium laptops) had a different sort of COM port called a 8250 as opposed to the newer 16550. On these machines the adjustment above is not available and the only solution is to try one or more of the following:

  • Close applications that consume processor time.
  • Turn off power management and / or screen savers during download.
  • Reduce the baud rate.
  • Buy one of the after-market plug in cards with the new sort of COM port.

Computers affected by this problem will almost certainly suffer the same errors in other communication packages. If it occurs rarely it will be masked by the automatic retry process in most modern e-mail and terminal programs.


See also the following article in the Microsoft knowledge base at