If you have installed DOS support under ArcaOS 5.1.x on a UEFI-based system, you may be able to gain another 64K or so of usable conventional DOS memory by disabling the Compatibility Support Module (CSM) in the system BIOS.
This 64K may be a game changer for applications using EMS, as conventional memory can run out of room for pointers to EMS locations. An example here would be Lotus 1-2-3 for DOS with a large spreadsheet.
It is also important to note that it may not be possible to disable the CSM on some systems, either due to BIOS restrictions or other system functions where the CSM is required for ArcaOS. However, in general, the Arca Noae Compatibility System (ANCS) should provide the necessary support for ArcaOS without the aid of the CSM. The good news is that if the system does not boot properly without the CSM enabled or if something doesn’t seem to function as expected, it can always be enabled again with no harm to the existing ArcaOS installation.
So, if you find yourself in need of just that little extra bit of conventional DOS memory, check the CSM setting in the system BIOS and see if you can disable it.
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