3.15.2. How do I tell how much memory my Lisa has?

You can use the Service Mode built-in to the ROMs to check the memory size, and do your own read/write tests to confirm it (although the self-test checks it pretty thoroughly).

To enter Service Mode:

press the space bar during the self test
"Startup From" the floppy drive (with no floppy inserted)
When you get the "no floppy" error, type Apple-S

The amount of memory is at location 2A8, so type this to see it:

  12a8[return]
  1[return]

The first two words of the data are the memory size in bytes, as shown below. Note that unlike intel chips, the 68K is big-endian; the high byte comes first.

512K 0008 0000

1M 0010 0000

1.5M 0018 0000

2M 0020 0000

4M 0040 0000

512K	0008 0000
1M	0010 0000
1.5M	0018 0000
2M	0020 0000
4M	0040 0000

More than 2MB is only possible with revision 3A ROMs, and CPU and memory board modifications.

Source: James MacPhail / LisaList 2006.06.26

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