INVADERS game on 2P

[nama]

So as some of you know I have a 2P MF, unfortunately with no micro floppy (MF), so it's basically a 2P except it boots to the H/D/M? prompt, so the ROM is not wired in a way that it accesses the BASIC in ROM. I have a few machine code only .LOD files that I got from the web and I load these into the C2-4P via serial. I had previously separated the .LOD files into working and non working folders. Just out of curiosity I tried to load a few of the non working ones again on the off chance that I missed something that was actually working. I loaded a few programs and as I suspected non worked just as before. then I loaded INVADERS, and I was very surprised when it suddenly started to work. I thought that was rather strange but promptly moved the .LOD file into the 'working' folder. Later I tried to load it again and it didn't work. The only thing I could think was that something I had previously loaded into RAM had caused it to work. I scratched my head and tried to remember what I had loaded before. After a few goes with various programs, I decided to load BASIC. A few months back I had extracted the BASIC code from OS65D in the hopes that I could load it over serial. Unfortunately I was not able to get it to function as the machine would just hang. However loading BASIC, the reseting the machine and then loading INVADERS would allow INVADERS to now function were before it would just hang...I love happy accidents.

Phil

[nama]

...Strangely enough I can't replicate this on my C2-4P which is setup almost identical to the 2P.

[Mark]

Hi,
I recall one of the .LOD files I had was missing an RTS as the last instruction before jumping to the run address. Depending on what you have in memory it would work or not. Could it have been Invaders? If it doesn't have one already make sure the .LOD file ends 20<cr>70<cr>02<cr>60<cr>.0222G or set $0AD8 to $60 The entry point is $0222, which sets 32col mode on the 540, and jumps to $0400...

-Mark

[dave]

Do I recall correctly that you mapped an 8K block to $A000 on the C4P? Did you do the same on the C2-4P?

A lot of 6502 machine language programs used the BASIC-in-ROM as a kind of library, since it was full of useful routines, and RAM was often tight. Add to that the relatively low code density of the 6502, the RAM and development time savings could be significant.

Dave

[Mark]

I built an OSI RAM/ROM replacement board ~25 years ago (!) where I swapped out the RAM at $A000 for an OSI BASIC EPROM. This reduced the RAM from 48K to 40K for OS65D, but it didn't care. The board uses CMOS static RAM which use a fraction of the power that normal OSI boards use, saving my power supplies. Back then I used those Radio Shack dry transfer sheets to layout a 2 sided board, but now it would be much easier using modern layout software and a board house or laser printer transfer.

I added a SPDT switch to the SYN600 mapping jumpers on the 505B board to switch personalities from a C4PMF to a C4P. (I also had to build an RS232/Cassette interface with baud rate generator to let me load old tapes.)

The board filled the 2K memory holes. An Extended Monitor was relocated to $E800 (EXMON requires the BASIC ROM I think) --handy for debugging, and RAM filled $C800. Looking back on this project, I should have put in a socket for the Cegmon/C2e ROM, though the mapping would have been a problem.
I found my notes on changing the 505B jumpers in case anyone wants them. You can just sort of see the 4 pin header I used to connect the SPDT switch to the 505B board in the center of this picture http://osi.marks-lab.com/boards/images/OSI505b.jpg (near the brown wire-wrap wire).

-Mark

[dave]

Hi Mark,

Your notes would be most welcome.

Great to have you here on the forum!

Dave

[Jeff]

Mark, this is a thing of pure beauty!

I would love to try and make one today with an additional 24k of ram for my C4P.

[Jeff]

Mark, do you know what those white bus connectors are called and if they are available to buy still?

Also, do you have any info on PBC houses that do one-offs at a reasonable price?

I'm sure you know what I am thinking!

[MK14HAK]

Dont forget : viewtopic.php?f=3&t=180

[Klyball]

Mark, do you know what those white bus connectors are called and if they are available to buy still?

Also, do you have any info on PBC houses that do one-offs at a reasonable price?

I'm sure you know what I am thinking!

these should work

http://www.digikey.ca/product-detail/en/0/WM3309-ND