EMS40.SYS Is Valid LIM 4.0 Driver for EM Use in Basic PDS (64591)

SUMMARY

EMS40.SYS is a device driver that emulates the Lotus/Intel/Microsoft (LIM) Expanded Memory Specification (EMS) version 4.0. This software permits AT-class machines with extended memory to adapt their extended memory (defined by XMS) to expanded memory (defined by EMS). This driver is compatible with Microsoft Basic Professional Development System (PDS) versions 7.00 and 7.10 and can map Basic PDS source code segments less than 16K in size to the expanded memory of the machine.

EMS40.SYS is freeware and it is available for downloading from the PC MagNet bulletin board. Although the source code is also available on MagNet, EMS40.SYS is already compiled and ready to use. Much of the information in this article comes from the "readme" file also available on MagNet.

MORE INFORMATION

EMS40.SYS can be installed as a driver specified in your CONFIG.SYS file with the syntax shown below. The drive and path should be specified so the system can find the driver during machine boot-up. Once installed, EMS40.SYS cannot be removed from memory without rebooting the computer.

   DEVICE=[LogicalDriveName:\][path\]EMS40.SYS [xxx]

The optional "xxx" parameter allows you to specify the amount of extended memory in kilobytes (K) to be used as expanded memory by EMS40.SYS. If the "xxx" parameter is omitted, the default value is 384K. By setting "xxx: to a smaller value than that of the extended memory installed, space can be reserved for extended memory programs, such as HIMEM.SYS.

EMS40.SYS maps extended memory into four contiguous 16K pages in conventional MS-DOS memory and permits access to memory in situations that otherwise could result in a "Memory Full" error. EMS40.SYS is not as fast as a dedicated LIM 4.0 EMS board and driver, but it implements (within the limitations of software emulation) all 28 functions specified in the LIM 4.0 EMS. It does not attempt, however, to emulate the DMA functions included in Function 28, Alternate Map Register Set.