If You Have Trouble Mapping Memory; If Emulation Memory Behavior Is Erratic - HP MC68040 User Manual

Chapter 9: Solving Problems

If you have trouble mapping memory

If you have trouble mapping memory
The emulator uses a best fit algorithm to assign memory blocks to map requests.
Because the memory block sizes available depend on the emulation memory
module installations and the use of the dual-port memory, it's possible that a
256-byte map request may use 512 Kbytes. (The map term will be only 256 bytes.)
Most systems won't have such differences between memory block size
requirements and available memory. However, certain emulation memory module
installations will aggravate the problem.
Also, use of the dual-port memory is controlled first by monitor selection and next
by explicit selection of a dual-port term in the map. If you choose a foreground
monitor, the dual-port memory block is reserved for the monitor. If you choose a
background monitor, and don't explicitly map a term with the dp attribute, the
dual-port memory may be used to satisfy any map request. For example, if you
request a 256-byte map term and this memory block is available, it will be used to
satisfy the request because it is closest to the needed size. Or, if you request a term
that is slightly larger than another available block, the dual-port memory will be
used with another map term to satisfy the request. (For example, a 260-Kbyte
request may use one 256-Kbyte block and the 4-Kbyte dual-port memory.)
Refer to the section "Mapping Memory" in Chapter 8, "Configuring the Emulator",
for more information on memory allocation.

If emulation memory behavior is erratic

Check to see if you have installed HP 64171A or HP 64171B memory modules on
the emulation probe board. These memory modules are too slow to work with the
MC68040 emulator. Use HP 64172A, HP 64172B, or HP 64173A memory
modules.
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