Comment by oblio
7 years ago
Read the article... Yes, obviously those CPUs didn't support it. But the later CPUs and PCs did, and yet the software (MS-DOS), didn't really support it. They had to use some gross hacks to access more memory.
That excuse is valid for 8086, but it's no longer valid for the 386.
Early DOS was designed to be as lightweight as possible so as much memory as possible was available to applications. Including expanded memory bank switching code and 32bit protected mode support on early primitive hardware that didn’t have those features anyway would have left little or nothing for actual applications to run in.
Even when expanded memory was an option, loading a bank switching memory extender to work around the cpu’s Address range limitations left less base memory left for non-EMM aware apps to run in. Many times I remember discussing with users the pros and cons of different memory managers and aporoaches, but most of the time in that era, not using them at all and using bare bones MS-DOS was actually the best choice. Some users would have two boot disks. One without EMM386 to run software that wasn’t expanded/extended memory aware to maximise the memory available to them, and another with EMM386 to run one or two apps that were.
Ems / xms was a hack to use the extra memory. Without those systems you would never see more than the base ram. These started out as 3rd party software before eventually becoming part of msdos. I still remember the sticker shock when buying a retail copy of EMM386. So I suppose 'support' is a bit weasely here.
Expanded memory cards did exist before EMM386, and could be programmed to map in 4×16 KB pages to D000 or E000: https://en.wikipedia.org/wiki/Expanded_memory#Expansion_boar...