[atari7800] Re: DMA TIMING

>Maybe the answer to my last question will help...

Thanks, Dennis, however, either I'm being completely dense, or everything I've 
read so far on the subject is indirect and circular (or maybe I've just 
frustrated and cranky that my "big breakthrough" of layered parallax scrolling 
may not be possible).

So I am going to make a some of very simple, very direct statements. I welcome 
anyone who can tell me if they are correct or not.

- DLLs, DLs and bitmap data may be in RAM *or* ROM. (True/False?)

- DLLs and DLs *must* be in RAM because ROM access time is too slow to be read 
by Maria. (True/False?) 
  - But somehow Maria is able to read bitmap data from ROM. (True/False?)

- RAM is accessed more quickly by Maria so it is generally preferable to put 
DLLs, DLs and bitmaps in RAM. However, for displays which are not overly 
complex keeping everything in ROM would be perfectly acceptable. (True/False?)

- The DMA TIMING values listed in the Software Guide are for data read from ROM 
 (True/False?)
- The DMA TIMING values listed in the Software Guide are for data read from RAM 
 (True/False?)
- The DMA TIMING values listed in the Software Guide are for data read from ROM 
or RAM, it doesn't make any difference  (True/False?)

I expect I'm coming off as a complete jerk here, and I appologise. However, my 
impression at this point is that if I rewrite my routines to use sprites 
instead of characters and put all bitmaps in RAM that it will work (128 bytes 
per line * 2 = 256 cycles or 128 bytes per line * 3 = 384 cycles either of 
which should leave enough time for overhead but the former would have the added 
bonus of being able to display other sprites on the layered scanlines). 
However, I don't have the timing values nailed down and I don't want to spend a 
day or day and a half in rewrites only to find out it's still not fast enough.

Thanks!!

Chris...

Other related posts: