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-
- These charts were created by Quarterdeck Office Systems, using
- Quarterdeck's Manifest program, in order to compare 16-bit
- expanded memory boards from different manufacturers. All boards
- used in this comparison were tested on a 6 mHz IBM AT with a VGA
- video card and 256K of active memory on the motherboard. We did
- not test boards that could not map pages of expanded memory at
- least as far down as 256K (segment address 4000H).
-
- Here is a brief description of the Manifest reports displayed:
-
- System/Config: The parameters on the memory manager's CONFIG.SYS line
- give some indication of how much effort may be required to configure
- the memory manager for use with DESQview, although some memory
- managers' setup programs place these parameters automatically. When
- we knew how to do it, we reduced the number of expanded memory handles
- provided by the manager to 16, a number adequate for most users'
- purposes; this reduction both decreases the RAM taken up by the memory
- manager and improves some benchmark timings. The presence of the
- DESQview driver QEXT.SYS in the CONFIG.SYS indicates that we were able
- to configure the board so that it provided a small amount of extended
- memory as well as expanded memory - a very important feature for
- DESQview users.
-
- Expanded/Overview: More than 16 total EMS handles in this section may
- mean that the driver's size and performance could be further
- optimized, as discussed above. The existence of real alternate maps
- is an important feature for DESQview users who want to run high-speed
- communication programs in expanded memory.
-
- Expanded/Timings: These figures are to some extent dependent on the
- speed of the RAM chips on the memory board, but an unusually low
- figure may indicate that the manufacturers have chosen to slow down
- the memory that they map between 640K and 1024K.
-
- Expanded/Pages: The more " + " signs (indicating mappable areas below
- 1024K) visible on this map, the bigger the program that can be run
- inside DESQview. All boards tested allow the mapping of expanded
- memory pages between segment addresses 4000H and A000H (256K-640K).
- As these tests were done on a VGA system, the most pages above 640K
- that any expansion board can be expected to map is four: one at
- B000H, one at B400H, and two between C800H and E000H. 80286
- computers do NOT allow the use of the E000H area by expansion
- boards; an 80286 memory management unit on the motherboard, like
- an 80386 memory manager, can access the E000H area and provide
- four more mappable pages.
-
- Expanded/Benchmark: Low timings here indicate superior performance in
- the handling of expanded memory calls. All rows of figures except the
- first row represent the time required to complete various EMS
- functions; the first row (Timer Interrupt Latency) indicates the
- amount of time that interrupts are locked during the different EMS
- functions. Which figures are most significant depends on what you do
- with expanded memory; more information is available in the Manifest
- manual.
-
- DOS/Drivers: The size of the driver labeled EMMXXXX0 indicates how
- much conventional memory the memory manager takes up. This figure can
- sometimes be modified by changing the number of EMS handles, contexts,
- and names provided by the memory manager.