Rockwell Automation 9323-S5500D A.I. SERIES MICROLOGIX 1000 AND PLC-500 SOFTW - Manual (Page 31)

MicroLogix 1000 and PLC-500 A.I. Series Software Reference
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RAM Considerations
PLC-500 A.I. requires an 80386 or faster processor and at least 3 M of extended
memory (XMS) free. If your system has less than 3 M of available RAM, the software
will be forced to use a swap file on your hard drive, which slows down many software
operations considerably.
Note If you are running under Windows, be sure to shell to DOS to check your free memory.
An ideal system would contain at least 8 M of RAM, where at least 3 M of RAM is
available after allocating some memory to a disk cache (such as MS-DOS’s Smartdrv).
The version of MS-DOS on your system also affects the amount of available RAM.
Although the software can run on MS-DOS 4.01 and 5.0, consider MS-DOS 6.0 as the
minimum version due to its advanced memory management features.
PLC-500 A.I. no longer has a minimum conventional RAM requirement of about
580K. As long as you have more than 500K free conventional memory (and at least 3
M of XMS memory free), you will be able to run the software without memory errors.