sichermn@beach.csulb.edu (Jeff Sicherman) (06/22/91)
In article <1991Jun21.082150.11675@csc.canberra.edu.au> act@softserver.canberra.edu.au (Andrew Turner) writes: [ deleted upgrade details ] > >3. Microsoft uses the following terminology to describe memory: > > BASE MEMORY : 0-640 Kb > (CONVENTIONAL MEMORY) > UPPER MEMORY AREA : 640 Kb - 1 Mb > HIGH MEMORY AREA(HMA) : 1 Mb - 1Mb+64 kB >Due to a feature on 286's and 386's real mode execution is available in the >HMA per the A20 address line. DOS loads Command.COM into this area if you >specify DOS=HIGH in CONFIG.SYS. NB COMMAND.COM has been totally rewritten and >is RE-ENTRANT!!. This adds memory overheads of about 2.8k, I assume for each >re-entry. You also must specify DEVICE=C:\DOS\HIMEM.SYS in config.sys. > >4. You will not be able to use your 384 Kb on the 286 as this requires >EMM386.EXE to be loaded. > >5. To quote Microsoft: > > "UMA support for 80286 class machines is not supplied in MS-DOS 5.0. > The choice to use EMM386.EXE as the engine for using Upper Memory > Blocks has been motivated by two major factors. > > 1. High Memory is available on both 80386 and 80286 machines. To > prevent having two drivers, one for each machine. > > 2. Development research indicated that UMB savings on 80286 class > machines did not offset the memory costs of the UMB driver nor > development time. > > MS-DOS 5.0 OEMs have shown interest in developing UMA capabilities > into their releases. OEMs do have options that were not addressed > by Microsft's project, options such as Hardware and Firmware > solutions." > >Comment: Sounds like 'bull....' to me. > >Summary: > Until I try it on our 286's with 640+384 I'm not sure but it seems >like unless you have memory in the HMA you get nothing! Does this mean that upper-memory (640K-1Meg) is not available for high-loading on anything less than a 386 machine using DOS 5.0 ? If so, this implies that QRAM (or the like) is still necessary for high (UMB) loading on 286-class machines ? Is he current QRAM compatible with DOS 5.0 ? In either case (DOS 5.0 works in UMB's or QRAM necessary), on an AST Premium 286 with EEMS, is there a minimum revision level of REMM.SYS required with either package ? Jeff Sicherman