Gears of War 5 - ZX Spectrum Version

 




Gears of War 5: ZX Spectrum Version



Ok, not really!

Another possible #WCCChallenge topic for this week was Gears. Seen as I'm on some sort of nostalgia trip today, I thought I'd rehash a very old routine that demonstrates a buffer technique in ZX assembly.

I used a Gears 5 wallpaper from some random wallpaper site, so I'm assuming it's fan art, converted it to a ZX Spectrum .scr file and then did some Z80 tomfoolery!

Simply put, you load the screen into a memory location and then use 12 bytes of code to move each byte of the screen data onto the ZX Spectrum's display.

The 12 byte routine goes like this:


    
	LD HL, 32768 ;(Source)
	LD DE, 16384 ;(Destination)
	LD BC, 6912  ;(Length)
	LDIR         ; Load, Increment Repeat (basically a loop until you move all 6192 bytes)
	RET	     ; return (go back to the BASIC routine)


Converted to BASIC:


    
10 CLEAR 32767: BORDER 0: PAPER 0: INK 7: CLS 
20 FOR n = 65000 TO 65011
30 READ a: POKE n, a
40 NEXT n


100 RANDOMIZE USR 65000: REM this is like a function in other languages. It basically calls the routine below


1000 DATA 33, 0, 128: REM LD HL, 32768 (Source)
1010 DATA 17, 0, 64:  REM LD DE, 16384 (Dest)
1020 DATA 1, 0, 27:   REM LD BC, 6912  (Length)
1030 DATA 237, 176:   REM LDIR         (The Copy Routine)
1040 DATA 201:        REM RET          (Return)

Use FUSE to load an image you've created into 32768 (6192 bytes long) then create a .tap of the code (zmakebas screen.bas -o screen.tap). Run the code and you should get your picture. Save as a snapshot and then you just need to load the .sna in future.

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