Chip RAM (Amiga 500)
A19If you are having issues with the chip RAM your best test is to chuck in a DiagROM, boot up the Memory Tests, then Extended Chipmem Test.
This test will test all chipmem even in the extended areas (upper 512k and extension port) regardless of if they are good or bad (as if bad they don't show up in AmigaDOS or Workbench etc...)
Interpreting the data is another thing.
Shown in extended memchip test at top as a bunch of numbers across the screen.
The first group is the upper byte (D8-D15), and the second group is the lower byte (D0-D7).
The third and fourth groups are just repeats of the first and second.
Beyond that they can also test the expansion port memory chips.
Here is an example where U21 D2 (pin 2) is faulty.
Notice the Checking Address is 0x00086400 which is higher than 0x0007FFFF so is the second 512kb of extended memory, making it U21 not U17.
As the memory is being tested, the following ranges are what is tested:
- 0 to 0007FFFF - 512kb Lower RAM (U16, U17, U18 and U19).
- 0008000 to 00FFFFF - Upper RAM (U20, U21, U22 and U23).
- 0010000 to 0020000 - Up to 1MB Expansion Port (Trapdoor)
NOTE: if you change the JP2 jumper to the top pin (A19, 0008000)
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