Search found 4677 matches
- Sat Feb 10, 2024 6:20 am
- Forum: Programming
- Topic: Recommendations for VIC-20 assembly tutorial, tools
- Replies: 10
- Views: 1618
Re: Recommendations for VIC-20 assembly tutorial, tools
To be specific, I have a copy of some VIC 20 Diagnostic firmware that has a bug when it comes to determining how to display on the screen (I get odd colors). Are you sure this is not due to a hardware bug (faulty colour RAM, for example) in your VIC-20 itself? In that case it would be a waste of ti...
- Sat Feb 10, 2024 5:42 am
- Forum: Programming
- Topic: Line drawing algorithm
- Replies: 20
- Views: 4133
Re: Line drawing algorithm
I was able to get it down to under 15 cycles per pixel on average? That would imply your routine accesses/modifies each involved bitmap byte only once, i.e.: having LDA - ORA/EOR/AND #imm - STA present and inlined for all 36 possible horizontal line segments, removing all further address arithmetic...
- Sat Feb 10, 2024 5:11 am
- Forum: Hardware and Tech
- Topic: Another ram expansion? Yes it is
- Replies: 25
- Views: 5639
Re: Another ram expansion? Yes it is
Mike sum[s] up the challenge with adding memory visible to the VIC chip, but, I made a prototype circuit that will fix this problem. Just for the record, I solved said "challenge" or "problem" years ago already with aforementioned VFLI mod, by installing the RAMx range memory on...
- Sat Feb 10, 2024 2:45 am
- Forum: Programming
- Topic: Need help with adding custom character set
- Replies: 6
- Views: 1082
Re: Need help with adding custom character set
How can I make sure the font file has the proper load address? The load procedure with SYS57809 ... SYS65493 that I highlighted above forcibly loads the font file to $1400, yet still a load address needs to be present as first 2 bytes of the file (making it 2050 bytes total). I have checked the fil...
- Sat Feb 10, 2024 2:17 am
- Forum: Programming
- Topic: Need help with adding custom character set
- Replies: 6
- Views: 1082
Re: Need help with adding custom character set
You normally would not want to do that as then the text screen and character set are at the same position.ricky_derocher wrote:What would be the poke(s) needed to set the font for $1000?
The first usable position for the font then is at $1400, see my edited post above for more details.
- Sat Feb 10, 2024 1:45 am
- Forum: Programming
- Topic: Need help with adding custom character set
- Replies: 6
- Views: 1082
Re: Need help with adding custom character set
Just "bload" the font 9 block font file into place, and then POKE the right address to change to the font. That works quite the same on the VIC-20. VIC register 36869 sets the character generator base address (bottom 4 bits) and the screen start (top 4 bits, together with the top bit of 3...
- Thu Feb 08, 2024 1:06 pm
- Forum: Hardware and Tech
- Topic: Another ram expansion? Yes it is
- Replies: 25
- Views: 5639
Re: Another ram expansion? Yes it is
I [...] saw your vfli mod, what you did there is superb, so you place 3k on the VIC side with hw mod. Is it possible to add more ram this way, i mean, can we add other blocks on the VIC side too? I know it is not much meaningful since VIC can utilize 4k but the display area could have been switched...
- Thu Feb 08, 2024 9:34 am
- Forum: Hardware and Tech
- Topic: Another ram expansion? Yes it is
- Replies: 25
- Views: 5639
Re: Another ram expansion? Yes it is
Is there a way to address this problem with this memory expansion? No. See here: https://sleepingelephant.com/ipw-web/bulletin/bb/viewtopic.php?t=10385&start=7&hilit=CPU+VIC+side , and to quote from there: The 6502 in the VIC-20 cannot tri-state its address bus, therefore the address (and d...
- Tue Feb 06, 2024 3:47 am
- Forum: Programming
- Topic: Resetting IRQs
- Replies: 10
- Views: 1325
Re: Resetting IRQs
Those 2 IRQs are not used for IO? The two VIA #2 timers control the timing of either the KERNAL IRQ (keyboard, jiffy clock, tape motor control) or the timing of tape load (T1 only) and save (T1 and T2). The VIA #1 timers produce NMIs (mostly for RS232 operations). It is somewhat possible to run sta...
- Mon Feb 05, 2024 4:30 pm
- Forum: Programming
- Topic: Resetting IRQs
- Replies: 10
- Views: 1325
Re: Resetting IRQs
;save the registers ldx #31 @ lda $9110,x sta $b9e0,x dex bpl @- That idiom isn't all that helpful to restore the state of the VIAs later - some of the registers (most notably the IER!) react differently to writes than to reads. Instead I'd simply do a SEI , then clear both IERs with LDA #$7F:STA $...
- Mon Feb 05, 2024 1:06 pm
- Forum: Other Systems
- Topic: Extremely Rare Ala Software game for C64 - Whiz Kid
- Replies: 12
- Views: 1771
Re: Extremely Rare Ala Software game for C64 - Whiz Kid
Thank you for dumping the tape, however as this is a C64 title it might be of minor interest in the VIC-20 Denial Games section. [...] if anybody has a means to convert it to a D64 file, that would be awesome. You should perhaps place that inquiry in one of the more numerous C64 forums instead. (mod...
- Mon Feb 05, 2024 6:19 am
- Forum: Programming
- Topic: Starting VIC-20 unexpanded-project UEFA European football championship 2024
- Replies: 5
- Views: 1318
Re: Starting VIC-20 unexpanded-project UEFA European football championship 2024
Loading longer programs from another program. [...] At the beginning of the program the locations 45,46,47,48,49,50 must be set with the correct values. [...] Calculate the space you need, calculate the address where the space must start. These are the memory-locations that must be filled with the ...
- Sun Feb 04, 2024 5:57 am
- Forum: Emulation and Cross Development
- Topic: Multipaint VIC 20 support
- Replies: 13
- Views: 3484
Re: Multipaint VIC 20 support
Perhaps an incomplete, multicolor-only MG mode would be still easy to add - and very useful for VIC 20 people... Multipaint saves also to some native formats, so it could have an option to save MG picture file. You could then do some hires edits/additions in Minipaint on VIC. Put the other way roun...
- Sun Feb 04, 2024 3:48 am
- Forum: Hardware and Tech
- Topic: Victor 6560 Replacement - Added graphics ops, just for fun
- Replies: 5
- Views: 1598
Re: Victor 6560 Replacement - Added graphics ops, just for fun
I am very well aware of that. :wink: Note though even for half axes 'just' in the range 0..255, the values in the work variables E, F, G, S, T, U and V can become rather large and need 32-bit registers to store them correctly. CBM BASIC can represent these numbers within its floating point format wi...
- Fri Feb 02, 2024 8:24 am
- Forum: Hardware and Tech
- Topic: Max screen size/area in pixels?
- Replies: 4
- Views: 1261
Re: Max screen size/area in pixels?
SparkyNZ, you try to draw conclusions from the document that are not in any way backed by what is actually the case: So working with a PAL monitor, I guess the maximum display resolution for any (non-VIC) signal would be 704×576? The TV norms as such do not define any horizontal resolution in pixels...