Hi!
No, you cannot use UMBs on anything less than an 80386.
Why that? On 386 or newer, you can map RAM from above 1 MB to UMB areas in software, but on older CPU, it can easily happen that your mainboard can support RAM which actually is in UMB areas. You could even use part of your VGA RAM as UMB when you never use monochrome or graphics, I guess.
There are exceptions but they are _extremely_ obscure and niche and do not apply here.
As said, this will depend on your mainboard etc. Computers with 8086 CPU are not likely to contain any more RAM than absolutely necessary, so people using those would rather buy EMS hardware ISA cards for those than install additional RAM in UMB areas. Computers with 286 and 386 CPU sometimes have the ability to support EMS, UMBs and shadow RAM as a feature of the mainboard chipset. You would have to use the mainboard-specific drivers for those. You sometimes find more generic drivers which know multiple chipsets, but those are usually rather for older than for newer mainboards :-)
FreeDOS is not a good choice of DOS for such a system. It's big.
In particular, if you have no 286 or newer, you will not have XMS or HMA, so the whole kernel will have to be in your low 640k RAM. You can still use the K-swap instead of XMS-swap version of FreeCOM: This lets you re-load parts of FreeCOM from disk instead of from XMS. The default version only supports XMS, which means default FreeCOM will block a lot of RAM on all computers which have no XMS available.
SvarDOS is smaller, but for an 8086 level PC, I recommend DR DOS 3.4. It gives you disk partitions over 32MB and it's tiny.
How about EDR-DOS? :-) You can also mix kernels and command.com shells from different versions of DOS, as well as different drivers. Regards, Eric _______________________________________________ Freedos-user mailing list Freedos-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-user
