SymbOS MSX multitasking operating system - help needed!

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By PingPong

Prophet (3332)

PingPong's picture

09-05-2006, 20:29

Prodatron, i've wrote a 'drawchar' routine that draw a 8x8 pattern requiring hl pointing to the charater shape, d=foreground color e=background color . This sub can draw at any x,y location. To give you an idea of much is fast i can draw about 768 8x8 patterns in less more than 1 second.

If you want, i can send you the source.

Regarding vdp command speed, as already said by artrag, depends much. However, to give an example:

Blitting an area in logical (pixel mode) can copy from a specified location to another location about 100000 pixels/sec. @50hz
Blitting an area in byte ( so called high-speed mode) can copy from a specified location to another location about 175000 bytes/sec. @50hz

If, you disable the HW sprites, you can increase the speed a little. For example:
with sprites on
Blitting an area in byte ( so called high-speed mode) can copy from a specified location to another location about 175000 bytes/sec. @50hz

with sprites off
Blitting an area in byte ( so called high-speed mode) can copy from a specified location to another location about 220000 bytes/sec. @50hz

By PingPong

Prophet (3332)

PingPong's picture

09-05-2006, 20:31

Umh, I forgot: it is not a proportional routine, it draws an 8x8 pixels area, using 1 bit per pixel font stored in RAM not VRAM

By PingPong

Prophet (3332)

PingPong's picture

09-05-2006, 20:36

Fill box operations are roungly 2x faster than copy operations. If you want bigger charaters maybe you can get decent result by submitting to vdp single box fill operations for each dot you want to draw. However this can be better that let do the hard work to the cpu only if you work with charaters bigger than 1 dot (for example x/y zoommed charaters).

By Prodatron

Paragon (1788)

Prodatron's picture

09-05-2006, 21:08

Thanx, PingPong, maybe your routine can be useful for chars inside the text line. I would be interested in the source (jmika at symbos dot de). Anyway I have more and more the feeling, that preparing a text line in the CPU memory and then copying it into the screen ram will be the fastest way.

Another problem: Currently I try to switch to screen mode 6 with this sequence:
di

ld a,8
out (#99),a
ld a,128+0
out (#99),a

ld a,32
out (#99),a
ld a,128+1
out (#99),a

ld a,0
out (#99),a
ld a,128+2
out (#99),a

ei

After this I set the palette like described here ( http://map.tni.nl/articles/vdp_tut.php#palette ) and then I write 256 bytes starting from address 0 in the VRAM. Unfortunately the screen stays completely black and empty. In the debugger, I can see, that the bytes have written correctly in the VRAM but I don't see anything on the screen.
Any idea what I did wrong?

By Edwin

Paragon (1182)

Edwin's picture

09-05-2006, 21:12

You need to set bit 6 of register one. This enables the screen.

By Edwin

Paragon (1182)

Edwin's picture

09-05-2006, 21:19

For practical purposes you need to set a few more registers though. I usually set the screen by writing the first 12 registers with an otir to port $9B. You can copy values for that from basic screens (easiest with an emulator) and change them as you figure out what you need.

By Prodatron

Paragon (1788)

Prodatron's picture

09-05-2006, 21:29

Great, now I see something Smile Now there is a repeat of the screen data every 8 lines. So you are right, I didn't initialize all necessary things. Where do I find the default values ("basic screens")?

By Edwin

Paragon (1182)

Edwin's picture

09-05-2006, 21:36

With that I meant, do a

10 screen 5
20 goto 20

and copy the values from debugger or something Smile

By Manuel

Ascended (15529)

Manuel's picture

09-05-2006, 21:37

check the regs in the emulator when you set it to a screen mode in basic.

By Edwin

Paragon (1182)

Edwin's picture

09-05-2006, 21:38

copied from my table:
Screen5Regs:
db 6 ; Set screen 5 plus disable horizontal retrace int.
db 2 + 32 ; Disable screen (!64), vblank int (!32), 16x16 sprites unmagnified (2)
db $1F ; Select page 0
db $80 ; Reg 3 unused in Sc5-8
db 0 ; Reg 4 unused in Sc5-8
db $ef ; Reg 5 low bits sprite attr table
db $0f ; Reg 6 low bits sprite pattern table
db 0 ; black background (col=0)
db 8 ; reg 8 (64k VRAM mode)
db $80 ; reg 9 NTSC + 212 lines
db 0 ; colour table hi bits (>16kb)
db 0 ; sprite attr table hi bits (>32kb)

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