Specifications

Page D-3Roadrunner AM-174 Programming Information
In versions of M68 appearing in earlier AMOS releases, the instructions
MOVECD7,CACR and CINVA were not implemented. With the release of AMOS 2.2C,
which includes M682.0(181), these instructions are now supported. Examples of their
use are shown above.
D.1.3One More Caution
The 68040 also has internal registers called Transparent Translation Registers (also
present on the 68030) that you must be sure not to modify. This is far less common
than instruction cache issues, but will cause system failure if modified.
D.1.4New Cache Control Program
Some existing third party software packages making use of self modifying code, which
worked fine with the 68030, will no longer work with the 68040 based Roadrunner. This
is due to the 68040’s large (4096 byte) instruction cache.
The ideal way to handle this problem is to have the software developer either not use
self modifying code, or to properly disable and enable the instruction cache as required.
However, you may find yourself in a position where a third party software developer is
no longer available, or is unwilling to make the necessary changes in a timely fashion.
As a solution to this problem, AMOS 2.2C and 1.4C include a new program called
COMPAT.LIT. This program works in conjunction with an ASCII file, which you create
using AlphaVUE, called COMPAT.DAT. Within COMPAT.DAT, you list programs that
can only be run with the 68040’s instruction cache disabled.
For example, the COMPAT.DAT file shown below would disable caching for the three
programs listed:
SCHDLP
INIJOB
;This is a comment
FAXUIT
Since there are no Alpha Micro programs that require the instruction cache to be
disabled, the program names used in the example are fictitious.
By using COMPAT, you can disable the instruction cache for selected programs, while
allowing other users on the system to run non-selected programs with the instruction
cache enabled.
Once you have created your COMPAT.DAT file, you can run the COMPAT program one
of two ways:
PDI-00172-10, Rev. A03