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Summary
Submitted by emu on 4 May 2016
Pentagram, the third and last Filmation Ultimate game is now available for the C64.
It runs almost as fast as the original Spectrum version and if you run it on a C128 in C64 mode it runs at the same speed as the Spectrum version.
Pentagram is the slowest of the 3 Filmation games (as it has more going on than the others) so a version of Knight Lore converted in the same way would run faster than this.
Mariusz did the original Z80 to 6502 conversion for the Atari 800 and I used his optimised 6502 source code and converted it to run on the C64.
Mariusz has done an amazing job of optimising the code for the 6502. This shows whats possible when code is optimised to run on the 6502 rather than the 6502 almost trying to emulate the Z80.
None of the C64 video hardware (hardware sprites) was used in this conversion, its just plain CPU grunt and memory. To use hardware sprites you would have to re-write most of the games rendering engine.
The full 64k is open with around 4k spare for possible future optimisations.
The 4k under $D000 is used and holds part of the screen display and video data. The code is so modular it was easy to switch the IO in and out as required.
It would be possible to free up another 3k or so by using a slightly slower Updatescreen routine (less rolled out) and write the colour ram data directly into colour ram rather than somewhere else first.
Rather than use a normal bitmap screen I used 3 banks of chars with raster splits to emulate a 256x192 bitmap display. This had the advantage of saving a couple of k for the display (6k rather than 8k) and also the screen memory runs continually as a 8bit block so its quicker to calculate the screen addresses when bliting sprites etc.
As well as supporting the extra speed of the C128 I have also built in support for the second fire button on CGS joysticks for the pickup/drop function for all you CGS joystick fans out there!
It should work fine on both PAL and NTSC machines.
Ive included the C64 source code as Im new to asm coding Im sure it can be improved on (Im no Ninja coder!). Its in Atari MADS format so you will have to compile it with that and then edit out the bytes 00,01,04,05 at the start of the created binary to create a runable C64 file.
Ive played it all the way through (with mega jump and unlimited lives cheats) and havent found any problems yet. Please give it a try and let me know what you think. |
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