MS-DOS 6 MEM Command Reports 384K for Adapter RAM/ROM (99008)

The information in this article applies to:
    Microsoft MS-DOS operating system 6.0

This article was previously published under Q99008


The MS-DOS 6 MEM command may display an incorrect value for Adapter RAM/ROM. On many machines, MEM displays a table similar to the following:
   Memory Type        Total =  Used  +  Free

   Conventional        640K     126K     515K
   Upper               139K     111K      28K
   Adapter RAM/ROM     384K     384K       0K
   Extended (XMS)     7029K    2781K    4248K

   Total memory       8192K    3401K    4791K
It is not possible to have 384K Adapter RAM/ROM and a value greater than zero for upper memory.


Adapter RAM/ROM

The value specified by Adapter RAM/ROM is calculated as follows:

1 MB (1024K) minus conventional memory, minus upper memory
block (UMB) space

Therefore, Adapter RAM/ROM is the sum of the following:
    Excluded UMB space
    Memory used by BIOS and adapter cards
    Expanded memory services (EMS) page frame(s)
However, on machines in which the amount of reported extended memory is below the 1 MB boundary (384K or less), MEM increases the value reported for Adapter RAM/ROM so that the total memory on the system is a multiple of 1 MB.

NOTE: The amount of extended memory reported is correct.


The upper memory area (UMA) is a range of addresses between 640K and 1 MB (1024K). This area is also commonly called the reserved address space.

Upper memory blocks (UMBs) are areas in the UMA that EMM386.EXE has reserved for loading device drivers and terminate-and-stay-resident (TSR) programs high.

Modification Type: Major Last Reviewed: 11/21/1999
Keywords: KB99008