Search found 4648 matches

by Mike
Sat Feb 10, 2024 6:26 am
Forum: Programming
Topic: "Ultimate Expansion" - new firmware for FE3
Replies: 58
Views: 9601

Re: "Ultimate Expansion" - new firmware for FE3

srowe wrote:I guess [the RTC is] used to set the timestamps of files written to the SD card.
This.

Unfortunately, many other (commercially available) SD2IEC drives economize on this aspect. :(
by Mike
Sat Feb 10, 2024 6:20 am
Forum: Programming
Topic: Recommendations for VIC-20 assembly tutorial, tools
Replies: 10
Views: 668

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...
by Mike
Sat Feb 10, 2024 5:42 am
Forum: Programming
Topic: Line drawing algorithm
Replies: 20
Views: 1050

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...
by Mike
Sat Feb 10, 2024 5:11 am
Forum: Hardware and Tech
Topic: Another ram expansion? Yes it is
Replies: 25
Views: 4118

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...
by Mike
Sat Feb 10, 2024 2:45 am
Forum: Programming
Topic: Need help with adding custom character set
Replies: 6
Views: 190

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...
by Mike
Sat Feb 10, 2024 2:17 am
Forum: Programming
Topic: Need help with adding custom character set
Replies: 6
Views: 190

Re: Need help with adding custom character set

ricky_derocher wrote:What would be the poke(s) needed to set the font for $1000?
You normally would not want to do that as then the text screen and character set are at the same position.

The first usable position for the font then is at $1400, see my edited post above for more details.
by Mike
Sat Feb 10, 2024 1:45 am
Forum: Programming
Topic: Need help with adding custom character set
Replies: 6
Views: 190

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...
by Mike
Thu Feb 08, 2024 1:06 pm
Forum: Hardware and Tech
Topic: Another ram expansion? Yes it is
Replies: 25
Views: 4118

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...
by Mike
Thu Feb 08, 2024 9:34 am
Forum: Hardware and Tech
Topic: Another ram expansion? Yes it is
Replies: 25
Views: 4118

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...
by Mike
Tue Feb 06, 2024 3:47 am
Forum: Programming
Topic: Resetting IRQs
Replies: 10
Views: 334

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...
by Mike
Mon Feb 05, 2024 4:30 pm
Forum: Programming
Topic: Resetting IRQs
Replies: 10
Views: 334

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 $...
by Mike
Mon Feb 05, 2024 1:06 pm
Forum: Other Systems
Topic: Extremely Rare Ala Software game for C64 - Whiz Kid
Replies: 12
Views: 672

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...
by Mike
Mon Feb 05, 2024 6:19 am
Forum: Programming
Topic: Starting VIC-20 unexpanded-project UEFA European football championship 2024
Replies: 5
Views: 377

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 ...
by Mike
Sun Feb 04, 2024 5:57 am
Forum: Emulation and Cross Development
Topic: Multipaint VIC 20 support
Replies: 13
Views: 2524

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...
by Mike
Sun Feb 04, 2024 3:48 am
Forum: Hardware and Tech
Topic: Victor 6560 Replacement - Added graphics ops, just for fun
Replies: 5
Views: 655

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...