8086/V20/V30, Win 3.0 and 'virtual memory'?

[krebizfan]

EMS requires more than just the 64kB of the page frame. The handles also have to be stored in conventional RAM. 2 MB under EMS 3.2 only needs 1 kB for handles but 4 kB under EMS 4.0. Go all the way to 32 MB of EMS 4.0 and another 64 kB becomes unavailable.

EEMS and large page frame EMS in EMS 4.0 was intended to prevent swapping entire applications to disk. Emulating those EMS functions in order to swap applications to disk seems rather roundabout.

One could emulate most EMS 4.0 on a XT but it would be slow and use too much memory to be very useful. EMS emulation makes the most sense with versions of Lotus before Lotus finally added the ability to handle files larger than memory available. That means EMS 3.2 satisfies all requirements for a XT EMS emulator.

 

[bhtooefr]

Ah, fair enough. So, basically, it's slow (as I expected), memory hungry (more so than I expected), and pointless, but you could do it.

 

[lameboyadvance]

Obviously having real memory available is preferable, but I was just thinking it may be handy for those times you wish to run a program (likely under Windows) that you simply don't have enough memory for.

 

[krebizfan]

Obviously having real memory available is preferable, but I was just thinking it may be handy for those times you wish to run a program (likely under Windows) that you simply don't have enough memory for.

If you want more memory under Windows 3 real mode, you would be best served by changing from Program Manager to the old MS-DOS Executive. Large numbers of color icons consumes lots of memory the system just doesn't have.

An EMS emulator does not provide much benefit under Windows. The major restriction on Windows memory management is programs that create data structures larger than 64kB. These can't be sent through EMS memory and just completely clog the Windows memory pool. Applications whose initial Windows version was in 1991 or later expect the big expanse of protected mode memory and handle running in real mode poorly. Using programs originally designed for Windows 2 will produce much better results with real mode Windows.

If you ever get bored, track down a copy of Petzold's Programming Windows in either Windows 2 or Windows 3 incarnation. It covers the complex design of real mode Windows memory management in great detail. 'Tis the stuff of programming nightmares.