SPEEDY
======


  Speeding up a C128 in C64 mode


  This code turns C128 into 2MHz when VIC is in the border rasters. You can
invoke it by jumping to the $c000, and to turn into normal mode you have to
jump to $c003. That is:
    sys49152   :   speedy is in charge
    sys49155   :   speedy is terminated
  You have to terminate speedy, whenever you want to access disk drives or
serial printers and such timing critical sections. You can use this utility
within your programs with a c128 detection. Your program decides whether
it is running on a stock c64 or a c64 mode of a c128 and if it's c128 the
code calls speedy when necessary. Speedy increases the performance by 40%
approximately. The measurements with MIPS program shows that:

speedy is off : 0.365 mips
speedy is on  : 0.511 mips

0.511 / 0.365 - 1.0 = 0.4 = 40% 




Here is the disassembled code of Speedy


;;
;; jump table:
;;  c000 : speedy is on
;;  c003 : speedy is off
;;
.
.,  C000  4C 06 C0   JMP $C006
.,  C003  4C 58 C0   JMP $C058
.,  C006  78         SEI  
.,  C007  A9 28      LDA #$28
.,  C009  8D 14 03   STA $0314
.,  C00C  A9 C0      LDA #$C0
.,  C00E  8D 15 03   STA $0315
.,  C011  A9 01      LDA #$01
.,  C013  8D 1A D0   STA $D01A
.,  C016  8D 0D DC   STA $DC0D
.,  C019  A9 FA      LDA #$FA
.,  C01B  8D 12 D0   STA $D012
.,  C01E  AD 11 D0   LDA $D011
.,  C021  29 7F      AND #$7F
.,  C023  8D 11 D0   STA $D011
.,  C026  58         CLI  
.,  C027  60         RTS  
;;
;; interrupt vector #1 (beginning of the border)
.,  C028  A9 01      LDA #$01
.,  C02A  8D 30 D0   STA $D030
.,  C02D  A9 32      LDA #$32
.,  C02F  8D 12 D0   STA $D012
.,  C032  A9 3D      LDA #$3D
.,  C034  8D 14 03   STA $0314
.,  C037  EE 19 D0   INC $D019
.,  C03A  4C 31 EA   JMP $EA31
;;
;; interrupt vector #2 (beginning of the visible screen)
.,  C03D  A9 00      LDA #$00
.,  C03F  8D 30 D0   STA $D030
.,  C042  A9 FA      LDA #$FA
.,  C044  8D 12 D0   STA $D012
.,  C047  A9 28      LDA #$28
.,  C049  8D 14 03   STA $0314
.,  C04C  EE 19 D0   INC $D019
.,  C04F  4C 81 EA   JMP $EA81
.,  C052  00         BRK  
.,  C053  00         BRK  
.,  C054  00         BRK  
.,  C055  00         BRK  
.,  C056  00         BRK  
.,  C057  00         BRK
;;
;; turning into normal speed, and tidying up the timing
;; you have to call this routine if you want to access serial port.   
.,  C058  78         SEI  
.,  C059  A9 31      LDA #$31
.,  C05B  8D 14 03   STA $0314
.,  C05E  A9 EA      LDA #$EA
.,  C060  8D 15 03   STA $0315
.,  C063  A9 00      LDA #$00
.,  C065  8D 1A D0   STA $D01A
.,  C068  A9 00      LDA #$00
.,  C06A  8D 0D DC   STA $DC0D
.,  C06D  8D 0E DC   STA $DC0E
.,  C070  8D 0F DC   STA $DC0F
.,  C073  A9 1A      LDA #$1A
.,  C075  8D 04 DC   STA $DC04
.,  C078  A9 41      LDA #$41
.,  C07A  8D 05 DC   STA $DC05
.,  C07D  A9 01      LDA #$01
.,  C07F  8D 0E DC   STA $DC0E
.,  C082  A9 81      LDA #$81
.,  C084  8D 0D DC   STA $DC0D
.,  C087  58         CLI  
.,  C088  60         RTS  
.,  C089  00         BRK  
.,  C08A  00         BRK  
.,  C08B  00         BRK  
.


Ilker Ficicilar
filker@newton.physics.metu.edu.tr
e068214@orca.cc.metu.edu.tr

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