Symbol PDT 7500 Series Product Reference Manual page 66

PDT 7500 Series Product Reference Guide for DOS
EMM386.EXE Device Driver
This driver provides alternate access to extended memory. This driver requires that
HIMEM.SYS be loaded first and uses the XMS API provided by HIMEM.SYS to further
manage extended memory.
Extended memory is "translated" into other types of memory such as Upper Memory Blocks
(UMBs) and Expanded Memory (EMS). UMBs allow additional RAM memory to be located
in unused areas of the first 1 MB of the address space. TSRs and drivers can be loaded into
UMBs via the LOADHIGH and DEVICEHIGH commands, leaving additional Transient
Program Area (TPA) available for application use. Expanded memory uses a 64K page frame
within the first 1MB of the address space to allow RAM to be mapped in 16K pages via the
EMS (LIM 4.0) API.
Note: Include this driver in the PDT 7500 configuration ONLY if UMBs or
EMS are required.
Recommended command line switches include:
1. If EMS memory is not required, add the following line to allocate all unused Upper
Memory Blocks for DEVICEHIGH and LOADHIGH commands:
DEVICE=EMM386.EXE NOEMS X=B000-BFFF
CONFIG.SYS DOS Settings
• BREAK = [ ON | OFF ]
Controls whether or not extended CTRL+C checking is enabled. Since this feature introduces
additional overhead and is useful only when a keyboard is attached, it should be disabled
under most circumstances. Off is the default setting; hence this command need not be used
unless this feature is being enabled.
• BUFFERS = n[,m] 1 ≤ n ≤ 99 0 ≤ m ≤ 8
Specifies the number of disk buffers to be allocated for use by DOS. The default value for the
PDT 7500 is n=15 and m=0. Many applications and environments request a larger setting.
Windows, for example, recommends a setting of n=20 and m=0. Using too large a value
wastes memory and using too small a value can reduce performance. Unless there is a specific
requirement, we recommend using the n=20 and m=0 settings.
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