Super-Slasher said:
I found a copy of EMM from MS-DOS and installed it into my Zenith, and it appears that I now have the full 1MB of memory addressable by the 8088 processor, but that leads me to another question.
If it says it's working, then it prob'ly is, I'd imagine. Although the 8088 can only address memory up to 1024Kb, the Expanded Memory Manager is able to "trick" the CPU into using memory which resides above 1024Kb. It does this by setting up a "page frame" within the 8088's 1Mb address space (in the "reserved" memory area, 640K-1024K). All that the CPU "sees" is this page frame, so it doesn't know that it is using higher memory. The memory manager maps the high memory into the page frame, thus into the 8088's address space. Therefore, you can use much more memory than just the 8088's 1024K (up to 32Mb), so if your board can hold more memory, feel free to use as much as you can put on it, or even add another EMS board someday.
Is this RAM totally useable by the system? What I mean is, is this EMS memory (384KB) as readily accessable as the base 640KB RAM is to the system, or can it be only accessed by high-memory devices, drivers and files?
Is the RAM available to the
operating system? Yes, but only with applications which are "aware" of EMS, which know enough to look for the page frame in the reserved area. Programs like spreadsheets, (Lotus 123) CAD programs, (AutoDesk) some games, and other memory-hungry apps generally can use EMS memory. Windows 3.0 is aware of Expanded memory, and uses it, so any program running under Win3.0 is using the memory too. Usually the documentation of those old programs will tell if they use expanded mem or not. DOS by itself does not use expanded memory, only the apps that run under it do. Later processors and apps use Extended memory, but a memory manager for such systems, like EMM386 use extended memory to
emulate expanded memory, for backwards-compatability with older soft- & hard-ware that uses expanded memory and not extended. Here's a link to more EMS info:
http://wombat.doc.ic.ac.uk/foldoc/foldoc.cgi?LIM+EMS
I'd still like to see the Zenith boot disk and EMM file, but this one seems to work as well. Strangely enough the EMM seemed to pick up the memory board without any parameters to be set, almost like plug and play. I set some parameters, anyways, to be safe.
Of course, you want your DOS startup banner to read "Zenith MSDOS 3.21", just for authenticity's sake. So check yr email, already...
--T