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Loading music

Cassette

Loading from cassette effectively uses all the CPU's time because you have to keep checking the cassette signal to see if it has changed, and you use a CPU timing loop to calculate length of signal.

So to do music and other things during loading requires precise timing. The C64 effectively had interrupt driven loading music and the serial chip handled clocking in of the data bits and signalled an interrupt when the byte of data was ready.

I think only Firebird games had loading music on cassette. The music was composed by Melvyn Wright (www.melright.com). The music data was embeded into the data on cassette. The data was read as a group of 3 bits and 8 data bits. The 3 bits determined if the 8 data bits were for data or for music.

This list is not complete, please add more. Will upload YM of the loading music soon.

Game	Loading music
Booty
Comet Game (The)	Media:Comet_game_(the)-loader.ym
Harvey Headbanger	Media:Harvey_headbanger-loader.ym‎
Thrust	Media:Thrust.ym
Spiky Harold	Media:Spiky_harold-loader.ym

Disc

The disc system on the Amstrad is "polled" which means the CPU has to keep checking if the FDC (NEC765) has more data to read/write. On the C64 the disc system is interrupt driven.

So to do music while loading requires careful timing and often the use of very small sectors (128bytes).

ZapTBalls

The Demo

5KB Demo 3

Games Which use hardware tricks (on old generation cpcs)

Useful if you want to dissect games to work out how they did it.

Please move to somewhere more appropiate

Page Flipping

Most good CPC games use the page-flipping technique in order to display sprites and/or scroll the playing area smoothly. In particular, two memory areas (instead of one) are reserved for the screen ram. In each frame, one of the two screens is displayed in turn, by using the hardware (exactly by changing the screen-offset, Reg 12 and 13 of the CRTC). At the same time, the next frame is being drawn in the non-visible screen until the next frame fly back signal. Then, the same cycle is repeated for each following frame.

The big advantage of this technique is that we can use a whole frame's machine-time for our code (with no animation problems that arise when we alter screen ram at the same time the electron beam displays it on the monitor). On the other hand, page flipping eats up a lot of memory area (which is crucial especially for 64Kb machines). This explains why a lot of games have very small game-areas !

Hardware Scrolling

This list is not exhaustive.

R3 used to make an approximate byte lenght horizontal scroll (not really smooth)
R5 used to make smoother vertical scroll (1 line)

Title	Year	Vertical	Horizontal	R3	R5	Confirmed
Action Force	1988	No	Yes	No	No	Yes
Anarchy	1988	No	Yes	No	No
Axys	1991	Yes	No	No	Yes	Yes
Bob Morane Science Fiction	1987	Yes	Yes	No	No
Builderland	1991	No	Yes	No	No
FlySpy	1986	Yes	Yes	No	No
Fusion 2	1988	No	Yes	No	No
Gothic	1988	Yes	Yes	No	No
Ghosts 'n' Goblins	1986	No	Yes	No	No
Jinks	1988	No	Yes	Yes	No	Yes
Killer Cobra	1987	No	Yes	Yes	No	Yes
Led Storm	1988	Yes	No	No	Yes	Yes
Legend of Kage	1986	Yes	Yes	Yes	Yes
Leviathan	1987	Diagonal	scroll!	No	No	Yes
Le 5eme Axe	1985	Yes	Yes	No	No
Mission Genocide	1987	Yes	No	No	Yes	Yes
Monty Python's Flying Circus	1990	Yes	Yes	No	No	Yes
Octoplex	1989	Yes	Yes	No	Yes(?)	Yes
Out Of This World	1987	No	Yes	Yes	No	Yes
Paraplane	1992	Yes	Yes	No	No
Prehistorik 2	1992	Yes	Yes	Yes	Yes	Yes
Prohibition	1987	Yes	Yes	No	No
Rick Dangerous 2	1990	No	Yes	No	No
Roland On the Ropes	1984	Yes	Yes	No	No
Sentinel (The)	1987	Yes	Yes	No	No	Yes
Skate Ball	1989	No	Yes	No	No	Yes
Skate Rock	1987	No	Yes	No	No	Yes
Skate Wars	1990	No	Yes	No	Yes	Yes
Star Avenger	1984	No	Yes	No	No
Stryker In The Crypt Of Trogan	1992	Yes	Yes	No	No
Super Cauldron	1992	Yes	Yes	Yes	Yes	Yes
Titan	1988	Yes	Yes	No	No
Ultima Ratio	1987	Yes	No	No	Yes	Yes
Warhawk	1987	Yes	No	No	Yes	Yes

Rupture (or splitscreen)

A technique to split the screen into more than one block vertically. (independant videoram offset) Used to hardware scroll one part of the screen while another is static. This list is not exhaustive.

Title	Year	Confirmed
Action Force	1988	Yes
Axys	1991	Yes
Dynamic Duo
Enlightenment: Druid 2
Grell and Falla
Mission Genocide	1987	Yes
Octoplex	1989	Yes
Prehistorik 2	1992	Yes
Skate Ball	1989	Yes
Skatewars	1989
Snowstrike
Super Cauldron	1992	Yes
Turrican	1990	Yes
Ultima Ratio	1987	Yes
Usagi Yojimbo
Xyphoes Fantasy
Sol Negro(opera)
Twin World (Ubi Soft)	1990	Yes
Warhawk	1987	Yes

Firmware

The following games are known to use firmware functions. This probably explains why they are poor. If the programmer had used the hardware directly they would have lots more cycles free which they could have used to make the game better.