For general info on I/O Ports, see:
* [[Standard Memory Expansions]].
=== Internal 64KB in 6128 and External 64KB RAM ===
This uses 1 bank, the bank is mirrored through the entire 512KB range.
e.g. c4,c5,c6,c7 access the same ram as cc,cd,ce,cf.
In terms of decoding the RAM selection byte:
11xxxsss
x = ignored
s = selection (0-7)
=== External 64KB Silicon Disk ===
The exact decoding is not known. Testing is needed to confirm.
=== 256KB RAM ===
This uses 4 banks (effectively 0-3 on 464 and 2-3 on 6128). It appears the 256KB RAM detects the 6128, possibly using /EXP but this is to be confirmed, so that it doesn't conflict with the internal RAM of the 6128.
The decoding looks like this:
110bbsss
b = bank (bank 0 is ignored on 6128 so that internal RAM is visible, 1,2,3 are from the 256KB RAM).
s = selection (0-7)
On 6128 you get 256KB RAM + internal 64KB base RAM
=== 256KB Silicon Disk ===
This uses 4 banks (effectively 4-7), the banks are not mirrored. The RAM doesn't conflict with the internal RAM of the 6128 OR the 256KB RAM. The decoding looks like this:
111bbsss
b = bank
s = selection (0-7)
On 6128 you get 256KB RAM + 64KB internal extra RAM+ 64KB internal base RAM
=== Bank Numbers ===
* 256K Expansion uses four 64K banks (bank 0..3)
* 256K Silicon Disc uses four 64K banks (bank 4..7)
The 256K Expansion and 256K Silicon Disc can be used together, resulting in 512K RAM in eight banks (bank 0..7). Plus, the 64K internal RAM is used (so total RAM is 576K).