FullHD81 - an improved video driver

[dr beep]

Still a question about your 9600 bytes size. When 6 lines are stored in 256 bytes, then I can store 200 lines in max 34x256=8706 bytes, so where is the rest needed for?

If you read again the first post, then you see that the unexpanded picture (320x240) requires 9600 bytes.

Btw. there are 2 other problems in your code:

Code: Select all

Cp 210 ; test for final line done in front, flag will be used after display
:
Jp lines+#8000

These 2 instructions use more machine cycles. The 2nd (and the 3rd in case of the jump) is a simple memory read (without /M1+A15), so the CPU will read some other than expected.

Just my thoughts written down ...

And I always really glad to read

Regards,
Zsolt

The instructions are the famous 48K bug when memory above 32K is available. On 16K this works. Used the trick in my 1K hires games. Solution is a copy of the routine on same memory above 32K. rework with extra register might get problems with timing.

Edit:
Preset HL to lines +#8000
Preset C to 209

Alter code
CP C
JP (HL)

Remain a gap of 17 tstates to be filled with
RET Z ; never true
LD B,B
LD B,B
LD B,B

[zsolt]

and I'm always really glad to read

[dr beep]

Thinking of doubling the displayroutine to make setting stack in unused bytes possible and just 50 bytes overhead in double displayroutine.

Screen will become larger at just a few bytes overhead.

[dr beep]

Looks like that in this way I can make screen up to 336 pixels without extra overhead but 50 bytes double displaybuffer.

[dr beep]

Timing is an issue. Need to fill 2 tstates.

[dr beep]

I think I can make it 328 with stack in open spaces.
Only thing needed is double displayline, so for app. 50 bytes more you get 200x8 pixels more displayfile.

[dr beep]

Yes,

Timing is perfect and stack on free spaces in screenarea.

Displayroutine will be 104 bytes. Screen will become 328x200.

Now I need a screen and first display and test on real machine.

[dr beep]

Code: Select all

Cp (hl) ; retnxtblock, start of hires
Ld a,h
Ld i,a
Ld a,l
Ld r,a
Defs 41
Ld sp,hl
Ld a,h
Add a,d
Ld h,a
Ret z
Ret z
Ld a,l
Add a,e ; ixpointer
Ld r,a
Defs 41
Ret

Ret z ; retinblock
Cp (hl)
Jp ix

Set in advance
Hl=#nn05
Ix=ixpointer+#8000
De=#129 , d=1, e=41

[dr beep]

Stack holds 4x retinblock, 1x retnxtblock
Final stack only holds outofhiresdisplay

[dr beep]

Wider screen can only be reached with a full display routine per line.
The stack will be too small.