Assuming you're still able to boot the C128...
1. Start the C128 in C128 mode.
2. Start the machine language monitor with F8.
3. Fill memory with zero's with the following command (this takes a while):
F 1C00 EFFF 00
4. Inspect the contents of memory with the following command:
M 1C00 EFFF
(use commodore key to slowdown, use "run stop" to stop)
5. All bytes should be set to 00; if you see bytes with values other 00
then one of the bits is stuck at one. Use the table below to
determine which DRAM chip is suspect:
01 - U38
02 - U39
04 - U40
08 - U41
10 - U42
20 - U43
40 - U44
80 - U45
6. If all bytes were zero, then there might be bits stuck at 0.
Fill memory with zero's with the following command:
F 1C00 EFFF FF
7. Inspect the contents of memory with the following command:
M 1C00 EFFF
8. All bytes should be set to FF; if you see bytes with values other FF
then one of the bits is stuck at zero. Use the table below to
determine which DRAM chip is suspect:
FE - U38
FD - U39
FB - U40
F7 - U41
EF - U42
DF - U43
BF - U44
7F - U45
The above test only checked bank 0 DRAM chips. Here's the DRAM mapping for both banks.
bank 0 1
bit
0 U38 U46
1 U39 U47
2 U40 U48
3 U41 U49
4 U42 U50
5 U43 U51
6 U44 U52
7 U45 U53
Can someone please tell us how to perform a similar test for bank 1 DRAM chips?
Wouldn't it be the same except issue command
F 10400 1FEFF 00
or
F 10400 1FEFF FF
??
Quote from: hydrophilicWouldn't it be the same except issue command
F 10400 1FEFF 00
or
F 10400 1FEFF FF
??
Thanks Hydrophilic. I wasn't sure if you needed to switch to that bank somehow before being able to access it using the monitor.