EMS Not Recommended with LAN Man, Windows 386 Enhanced (97872)

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Expanded memory managers differ from expanded memory hardware. Software emulators each behave with some unique characteristics and may even behave differently from version to version. An emulator that breaks in one environment may work fine in another.

EMM386 is an emulator type, which depends on protected mode mechanisms. The emulation is much slower than hardware and during the switch locks out interrupts.

If expanded memory is used too frequently, the system spends too large a portion of its bandwidth just switching, and this increases the periods during which interrupts are not serviced. Users sometimes hang when interrupts are missed, due to driver situations.

One of the most common problems with expanded memory emulators, is dropped characters in serial communications applications at high data rates, although some applications might be able to hide such troubles under certain conditions. Another problem is hanging up an environmental shell, such as Windows.

Recent versions of the NETWORK.WRI file for Windows 3.1 state that if you are running Windows in 386 enhanced mode, using expanded memory with LAN Manager is not recommended because it may downgrade system activity. (One version said downgrade or HALT; this difference is due to the unpredictability of system performance factors when expanded memory is involved.)