Display list in banked memory

[TGB1718]

I think I know the answer, but thought I would ask, in a 130XE, you can switch banks so that both CPU and Antic

access any combination of main/banked memory to the windows starting at $4000.

 

But if you switch to Antic only to extended memory, is that only for the display memory only, not the display list ?

I've had a bit of a play and it seems to me the display list has to be where the CPU also has access.

 

So in a nutshell can Antic access a display list in extended memory while the CPU is accessing main memory.

Hope that's clear what I'm asking

 

The reason I'm asking is I have a program that's manipulating the display list on the fly and it's taking quite a bit

of CPU time to do it, I was thinking of using the extended memory to place a load of display lists and just switch

to the appropriate one, saving a ton of CPU time.

I have a load of graphics data currently sitting between $4000 and $77D5 in main memory

[Rybags]

When you tell Antic to use extended banking, then any normal read access by it to $4000 - $7FFF addresses will hit whatever bank is selected.

That includes DLIst, display Ram, PM graphics.

If you have need to manipulate DLists then there's plenty of options.  You could cycle through 2 or more, performing updates on one while the other is active.

The time to change PORTB bank isn't much different than changing 2 bytes of DList pointer.

If you disable the OS Stage 2 VBlank you can even chain DLists together using the JVB at the end to point to the next one to run from, though potentially it could become a pain to debug.

 

Edited July 8, 2023 by Rybags

[woj]

It creates a nice opportunity to ask a question that passed through my head a couple of days ago and that I once before found an answer to by googling, but for whatever reason cannot find anymore:

 

What is the neatest / least display disruptive way of detecting extended memory with independent CPU/Antic access? I think the answer I once saw involved a temporary DL with one DLI setting a flag or something along this line...

[Rybags]

I think I posted an answer to that one elsewhere last week - yep, the DLI method was one.  The other could use a setup PM collision to do the detection.

 

[woj]

4 hours ago, Rybags said:

I think I posted an answer to that one elsewhere last week - yep, the DLI method was one.  The other could use a setup PM collision to do the detection.

 

Found it, thanks! Though it was last month  Regardless, I still want to find the code snipped I once saw, I think it might have been on the PL forums, yet I am unable to locate it again...