NYYRIKKI's MSX ROM loader for SVI

Who would have thought that we ever would get a NYYRIKKI emulator But impressive work, and finally some light for this forgotten generation of early SVI adaptors...

Thank you for your kind words... Indeed I'm also quite impressed, how well this program actually works. Most of the games don't have any problems! Seems that virtual me is doing a good work, LOL

Ah, I see... I thought the downloads database was for MSX programs only.

Yes... The routine works so that you point a byte with HL and call the detection routine. It will simply return "Yes, this is likely Z80-code" or "No, I don't think I should execute this" in a C-flag.

The actual detection is combination of tests... As we all know you can't look a byte and say what it is meant for, but we need to take a look at a big picture and what context the byte is. For humans this is quite easy, so I just tried to copy my own thinking process in to the code.

To evaluate the code I count "likely events" and "unlikely events" and in the end number of these events define the result. First I take a few dozen bytes back from the location and step trough the code until I'm back in the address. If I accidentally jump over the command byte that I was expecting to patch then this is unlikely event... As you might have noticed programs tend to start stepping correctly very fast even if you start from wrong byte because Z80-commands have different lengths...

After this I actually read what the code does if it is executed from the interesting byte forward... If I can see for example command series like: LD L,D / XOR A / LD HL,#6512 then I can say that this is very unlikely to be Z80-code as L-register is overwritten before it is used to anything. -> Unlikely event. If I see call to address range #200-#3FFF -> Unlikely event. If I see program trying to write it's own ROM or BIOS -> Unlikely event. If I see command like LD E,E -> Unlikely event. If I see call to address where previous command in memory is RET or JP -> Likely event.

I think you get the idea... If the code is packed then there is no much that I can do... How ever this is quite unlikely as most ROM's expect MSX to have only 16KB RAM and it is usually used to store variables. If something is packed in ROM it is more likely graphics. For sure there is always the one program that proves that I'm wrong (hello Beepertron) but mostly my logic seems to work. From the start I understood that this kind of program can't be 100% but I focused to things that are most likely/unlikely and in the end putting these things together made the end result surprisingly rock solid.

Thank you. The good thing in this project is that there was no boring moments while working on it. Although the code separation was very interesting problem the actual patching was just as interesting...

I give you an example from "Gommy medieval defender"... The music player in the game looks like this:

	XOR A
	LD C,#A0
	LD HL,#D615
LOOP:	OUT (C),A
	INC C
	OUTI
	DEC C
	INC A
	CP #D
	JR NZ,LOOP

After my program has done patching the routine it looks like:

	XOR A
	LD C,#8B
	LD HL,#D615
LOOP:	OUT (#88),A
	INC C
	OUTI
	DEC C
	INC A
	CP #D
	JR NZ,LOOP

Making that to happen automatically also requires quite a fuzzy logic.

Hmm... That is not a bad idea...

Not at all, and quite possible, but we would need to think on some changes for Interrupts and sound.
On sound, for instance, as the chip is not the same, instead of an out, we need to call a routine. As that uses more bytes, most of the time I need to "transplant" part of the original code to some specific calls.
Sometimes, I can use an RST, but some games use them all. Maybe with RST 0...
About BIOS, I'm more flexible than the majority of other users, so, the original copyrighted BIOS is included into the ROM file. There's no C-BIOS for Coleco as far as I know.

Last, but not least, maybe it's a good idea to improve the sound emulator. I already "open-sourced" (posted full source code) of the latest one here. It's like a proof of concept that I did in some hours to test noise emulation.

here: http://www.msx.org/forum/msx-talk/software/sn76489-simulator...

Maybe, you two guys would like to take a look.

The original one is way faster than that, but lacks noise completely.

That is not a very big issue... The AI has enough information of Z80 internal working that it can make enough room without breaking the code as long as we just have enough RAM space to move stuff into. I think I only need to add some special logic in case OUT is followed by JR / DJNZ

Yes, this is the approach I also used for MSX ROM loader... As C-BIOS does not have BASIC I used RST #0, #8 and #18 for better purposes (In, Out & other I/O) This way I didn't need to start moving things around. I think RST #0 would be enough to get all functionality in, but it would require quite a much translating things back and forth with tables... Maybe in this case "transplant" is better idea anyway...

No, but luckily I found disassembled version of the ROM that I think we could use.

My knowledge of Colecovision and it's sound chip at the moment is close to 0, so don't expect much help from me. How ever this is interesting stuff and maybe together we could make something out of this... Too bad that the time I have for these MSX (and related) projects is so limited... Please don't expect me jumping right in to this new project. I have also lots of other things WIP.

actually I already have the BIOS fully converted and it goes from 0 to 1FFF. You can check that on the files I've sent you.
Most of the "extras" I had to add, like joystick emulator and sound chip emulator, are already placed after $2000.
I boot @ 4000 with a small routine that copies (sometimes depack) the bios and extras to 0 and then I jump to that area to fix the game on the right position 8000 and beyond. Coleco RAM is just 1k, at page 1 (don't remember exactly where) but it's mirrored somewhere else.

Have you got the email?

c'mon!
On a small community like ours, if we don't join forces, we'll soon disappear...
Finnish parties like these are still happening?
Amazing Skis BTW!

@hbarcellos I've looked what you have done and I must say that you have already made almost general Colecovision emulator... Seems that practically only the automatic patching is missing... This project should be walk in a park. -> Just plug in AI

@Nyyrikki: please consider adding support for the Franky card also. It just needs another address for the VDP, but the vdp also has the compatible coleco soundchip inside. And thanks for your code, however Dennis is currently to busy to patch the sega romloader. I hope he'll find time later.

Ah, so you do read that mail address In case you get to patch the romloader, please contact me first... The AI is still under development and it has improved quite a bit since I wrote to you...

I haven't even heard about that, so I can't really tell... I know only the MSX emulation program by H. Klopper and P.Zevenhoven (Adaption Electronics Nederland) that mostly run only BASIC-programs.

Thanks for making this NYYRIKKI. I recently acquired myself a Spectravideo SV328 (I had one for about a year when I was 6-7 years old) and it's great to not just be limited to SV-specific software (which there isn't terrible much of).

- I understand that it converts an MSX-ROM to a SVI-ROM (using lots of magic). I might be able to try running the converted files on a real PCB in my SV-328 in the future and I can experiment it with already now in openMSX, but is it somehow possible to add a cassette loader and be able to load them this way as well? I think I saw this mentioned somewhere, but wasn't sure if there's an automated way to do that.

- When I googled on this I saw that you posted a new version (MSX_ROM-load_for_SVI_v1.3.zip) on a Facebook group. I don't have Facebook anymore however and I couldn't get the link to download, could you maybe post it in here as well?

(My first post here, so hi!)

Hello NYYRIKKI. While searching online a while ago I think I saw a mention of a newer version of this utility, now I can't find where I saw it. Could you perhaps post it here and describe what's has been updated? Thanks in advance.

Thanks! Will give it a spin when I find the time