Appendix 3: Ems Technical Reference; A3.1 Expanded Memory Definition - Everex EV-159 Owner's Manual And Reference Manual

Appendix 3.'
EMS
Technz'cal Reference
Applications programmers writing software for the EMS
mode on the RAM 3000 Deluxe should refer to the Lo-
tus/Intel/Microsoft (LIM) specification, Version 3.20, re-
leased September 1985. Use of this document will facilitate
portability to all EMS-compatible expanded memory cards.
A3.1 Expanded Memory Definition
Expanded memory is a bank switching technique that in-
creases the memory capacity of the PC up to eight
megabytes beyond the present DOS memory addressing
range of OK-640K (OOOOOH-9FFFFH). A 64KB window
(called a
page frame)
is located between the 640K and %OK
(AOOOOH-EFFFFH) reserved area boundaries. The page
frame is divided into four contiguous 16KB pages. The EMS
mode on the RAM 3000 Deluxe is divided into 128 16KB
blocks, totaling two megabytes. By sending commands to
the control circuitry on the RAM 3000 Deluxe, the
EMM.SYS expanded memory manager can map anyone of
these blocks into any of the four pages. Refer to the
Lotus/Intel/Microsoft (LIM) Expanded Memory Specifi-
cation (Version 3.20), September 1985 if you need a more de-
tailed explanation of expanded memory.
72