Oh, the rom isn't 8kb... 
$ openmsx test.rom warning: (uncompressed) ROM image filesize was not a multiple of 8kB (which is required for mapper type Mirrored), so we padded it to be correct. But if the ROM you are running was just dumped, the dump is probably not complete/correct!
By the way, that was a pretty heavy necropost 
$ openmsx test.rom warning: (uncompressed) ROM image filesize was not a multiple of 8kB (which is required for mapper type Mirrored), so we padded it to be correct. But if the ROM you are running was just dumped, the dump is probably not complete/correct!
By the way, that was a pretty heavy necropost 
How can I pad the rom myself to be a multiple of 8kb.
I thought you could do it with another 'org' statement at the end of the source code, but I didn't get it to work (used org '&c000'.
ds -$ & 3fffh
Where in the code need I put this instruction?
Where you need the padding, in this case, at the very end.
It inserts the padding needed until the next multiple of 4000H. In other words, it aligns to 4000H.
It works by taking the 2’s complement address of the current location (negating), and then ANDing it with a power of 2 minus 1. It needs to be a power of 2 so that you get a binary number of all zeroes followed by all ones. This masks out all the bits and this is what calculates the alignment to a specific multiple.
For example, say we’re at address 42H, its 2’s complement is 0xFFFFFFBE. We want to align to 4000H (2^14), minus 1 is 3FFFH, or in binary 0011111111111111B. The result in this example is 3FBEH, which is the number of bytes you need to add to 42H to reach address 4000H.
The result is the same for e.g. 4042H, -4042H is 0xFFFFBFBE, AND 3FFFH is 3FBEH, and adding 3FBEH to 42H is 8000H. This is where you can see why the AND is needed.
If you want to just pad to a specific size, let’s say 128K, you can more simply write:
ds 20000H - $
If your code becomes greater than 128K, this particular calculation will give a negative number and cause an error, saying that you can’t DS a negative amount (define negative space). You will need to increase the padding.
Thanks for the in depth explanation, got it working (on blueMSX). With pasmo it was 'ds -$ & #3fff'.
