Search found 4648 matches

by Mike
Sun Feb 18, 2024 3:47 pm
Forum: Programming
Topic: Can the display window be re-triggered? (was: 9001 when read?)
Replies: 8
Views: 652

Re: Can the display window be re-triggered? (was: 9001 when read?)

No. The display window is only triggered once per frame (when $9004 compares equal to $9001), i.e. you can't restart it after it ended by writing a corresponding higher value into $9001. What you *can* do is filling part of the display window with characters in multicolour that use %01010101 (85 dec...
by Mike
Sun Feb 18, 2024 3:56 am
Forum: Games
Topic: Multiplayer VIC20 Games
Replies: 5
Views: 406

Re: Multiplayer VIC20 Games

Especially unexpanded for extra charm. What's the point of advocating the use of an essential non-standard hardware extension and at the same time 'disallowing' the use of RAM expansions? No - it wouldn't add any 'extra charm' to me. It just places an unnecessary restriction on any related endeavou...
by Mike
Sun Feb 18, 2024 3:44 am
Forum: Programming
Topic: "Free ZP" which ones?
Replies: 6
Views: 243

Re: "Free ZP" which ones?

$2A $52 $FB - $FE I wouldn't be that sure about $2A and $52. Even though there are no direct ZP operand fields of instructions in the BASIC interpreter that point to these two addresses, these two addresses are part of temporary float values (actually their 5th byte) and might be referenced by indi...
by Mike
Sun Feb 18, 2024 3:33 am
Forum: Programming
Topic: "Free ZP" which ones?
Replies: 6
Views: 243

Re: "Free ZP" which ones?

heaven6502 wrote:what are the ZPs which are really free? :)
Just $FB..$FE, actually.

...

You find more details in this post of mine. :)
by Mike
Thu Feb 15, 2024 1:41 pm
Forum: Programming
Topic: Playing better notes
Replies: 1
Views: 176

Re: Playing better notes

You probably mean this one: 10-Bit Oscillator Frequency Resolution
by Mike
Tue Feb 13, 2024 4:15 pm
Forum: Programming
Topic: Line drawing algorithm
Replies: 20
Views: 1037

Re: Line drawing algorithm

MrSterlingBS wrote:the Demo [...]
... uses overlapping sprites to render filled vectors on the C64 which is a method that does not transfer at all to the VIC-20 (again, that method is nothing spectacularly new. The demo "Snapshot" already did so in 2010, see the part at 7:14).
by Mike
Tue Feb 13, 2024 12:10 pm
Forum: Programming
Topic: Line drawing algorithm
Replies: 20
Views: 1037

Re: Line drawing algorithm

http://www.quiss.org/boo/ "BRR" is nothing new and effectively is an 8-bit 'randomized' DDA . It is illusory to assume a line routine plots ~200000 pixels/second just because the 'deciding' part within it executes in 5 cycles. This is completely ignoring the other necessary parts of the r...
by Mike
Mon Feb 12, 2024 12:39 pm
Forum: Collecting and History
Topic: How to convert Tap files to D64?
Replies: 11
Views: 297

Re: How to convert Tap files to D64?

Transferring all these files from *.tap to *.d64 is only doing half the job. The tape original very likely assumes (and can rightfully do so!) it was run from tape, and issues further load commands from tape. You would at least need to identify those code sections that load the next files and adapt ...
by Mike
Mon Feb 12, 2024 11:20 am
Forum: Collecting and History
Topic: How to convert Tap files to D64?
Replies: 11
Views: 297

Re: How to convert Tap files to D64?

When this can't be done by just LOAD from tape and SAVE to disk (within VICE, for example), this more or less amounts to do a full crack. Even when there's no fast loader involved, the game can feature an autostart, binary non-BASIC program data (like machine code, character sets or level data) and ...
by Mike
Sun Feb 11, 2024 2:57 pm
Forum: Emulation and Cross Development
Topic: Corrupt end of basic program
Replies: 7
Views: 263

Re: Corrupt end of basic program

And I start the program with setting the pointers after chaining. The values in addresses 174 and 175 are only valid immediately after LOAD ! If you in-between edit the program and re-start it, indiscriminate copying of 174/175 to 45/46 will reference the old values, possibly truncating the program...
by Mike
Sun Feb 11, 2024 2:40 pm
Forum: Programming
Topic: Line drawing algorithm
Replies: 20
Views: 1037

Re: Line drawing algorithm

MrSterlingBS wrote:00,00 to 99,99 5516 per pixel 39
That should be 55 cycles/pixel.

You are improperly using the Euclidian distance here to pretend the line was 141 pixels long. The rasterization of lines with Bresenham plots max(dx,dy)+1 pixels, which is also 100 in the diagonal test case.
by Mike
Sun Feb 11, 2024 2:37 pm
Forum: Programming
Topic: VIC-20 joystick - which is the real way?
Replies: 5
Views: 233

Re: VIC-20 joystick - which is the real way?

I did not know much about VIC-20 hardware during the time I had one, but on my Radio Shack Color Computer I am aware that there were certain I/O registers that were ghosted, [...] ... or mirrored ... [...] and would appear in multiple places. Is something like this happening here? Not here, in a ce...
by Mike
Sun Feb 11, 2024 5:07 am
Forum: Emulation and Cross Development
Topic: Corrupt end of basic program
Replies: 7
Views: 263

Re: Corrupt end of basic program

Hi, I only use VICE. It happens 10% of the savings, and mostly at the end of the disk-directory or at the end of the tape. I made backups. I made a backup of this program with this error and didn't touch it after that. The backup is fine, curious. Other strange thing: I make backups of the floppies....
by Mike
Sat Feb 10, 2024 6:36 pm
Forum: Emulation and Cross Development
Topic: Corrupt end of basic program
Replies: 7
Views: 263

Re: Corrupt end of basic program

What tool did you use to create the program file in first place? This error is typical for a BASIC program file that for whatever reason was saved with a missing last byte . By itself, the SAVE command of BASIC does not produce that problem - but once a BASIC program is loaded that has been produced...