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Expanded Memory - Causing Computers To Lock
DocumentID: 651879
Revision Date: 29-Feb-96 8:29:10 PM

The information in this document applies to:
WordPerfect® 5.1 for DOS

Problem

Symptoms: Random stations on a network lock when retrieving a file. Solutions: The expanded memory manager is a device driver that is called from the CONFIG.SYS file. It is a device driver that essentially converts any extended memory to expanded memory. This is done so that applications that require and or use it will run correctly on the PC. WordPerfect is designed to take advantage of expanded memory whenever possible.

When WP executes, it does many different things. One of those things is write overlay files to memory. This memory can be conventional, extended or expanded. Once the file has been written to memory, WordPerfect verifies that the overlay file is in one piece and in the same location in memory where it was originally placed.

In all releases of WP 5.1 prior to the 06/29/90 release of WordPerfect, a DOS call was used to do this, entitled FIND FIRST; it basically searches the directory sequentially looking for the overlay file. If it finds the overlay file, all is well; if it does not find the file, it returns the error, "Can't Find WP.FIL" and, in most cases, locks. In many cases there was no way to know why the computer locked. This method did not verify the integrity of the overlay file in memory and was very slow.

With the 06/29/90 and 08/20/90 releases of WP 5.1 the method of verifying the WP.FIL file was changed to help the user and Customer Support understand why the error was occurring. This was done by changing the way overlay files are verified by using a CHECKSUM routine and introducing the numbered codes that are associated with the error e.g., {0}, {65335}. The most common of these is the "Can't Find WP.FIL {0}." The 0 code informs WP that the new method of verifying overlay files failed.

The CHECKSUM routine adds up the bits in the overlay file written to memory and compares that with what is on disk. If there are any discrepancies, the error is displayed and, in many cases, the computer will lock.

The 0 helps WP understand where the problem is and what to look for. If the file is being written to expanded memory, then WP starts checking to see if the memory manager is up to date and compatible with the 3.2 and or 4.0 LIM standards. This is a must. It is possible that the manager does conform to the LIM standards and still causes the CHECKSUM to fail and WP to generate the error. In this case it is a good idea to check the CONFIG.SYS and see what is happening with respect to the memory manager itself.

QEMM.SYS by Quarterdeck is an example device driver. When this device driver is used a line will appear in the CONFIG.SYS that looks like this:

DEVICE=C:\QEMM\QEMM.SYS

This line calls the device driver and converts the extended memory to expanded memory.

It does not specify the PAGE FRAME. The page frame is an address in the system memory (like a window) that allows applications to address the rest of the memory in the PC. It doesn't exclude any other areas of memory where other devices and or drivers may be sitting, such as network or video cards.

It is possible that conflicts can occur if the PAGE FRAME tries to use the same memory address already in use by another device. The same is true if the page frame is set, and some other device tries to use the same memory address. If this condition exists, the CHECKSUM will fail, and WP will lock because the page frame has been damaged and the overlay files have essentially been lost.

To avoid this situation, Problem Resolution is suggesting that all users of expanded memory managers exclude (set aside) memory address being used by video and network cards where applicable and set the PAGE FRAME. The methods of doing so vary depending on the type and version of expanded memory manager.

To exclude the memory address's for the network and video card and set the page frame using Quarterdeck, the following additions would be made to the line in the CONFIG.SYS where QEMM.SYS is being called.

DEVICE=C:\QEMM.SYS exclude=c800-cbff frame=d000

This will help eliminate the problems associated with this error.

Answer:

Details:


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