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I desoldered the BIOS from my SMS-2 and fitted a socket so I could try different BIOS versions.

The Japanese BIOS (posted by Zoop earlier) works fine, plays all games as expected. Funnily enough I thought fitting a Japanese BIOS would put the SMS into Japanese text mode, but evidently not! I still have no clue how a language switch might be implemented.

The US BIOS (bios13.sms) is an odd one though - upon power on it displays the logo then goes straight into the snail maze game, regardless of what you press or what game is inserted. I can't get it to do anything else.

Is this a bad dump, or has the bios been hacked in some way?

Mike

Quote

> Is this a bad dump, or has the bios been hacked in some way?

I'm not sure. I didn't dump it myself but I have heard some models of the SMS behave this way.
(if no cartridge is inserted it jump to the snail game directly)

Quote

> > Is this a bad dump, or has the bios been hacked in some way?

> I'm not sure. I didn't dump it myself but I have heard some models of the SMS behave this way.
> (if no cartridge is inserted it jump to the snail game directly)

But this one jumps to the snail game regardless of whether a cartridge is inserted or not!

It may be to do with the fact that I'm using it on a Master System II - funny that the Japanese one should work fine though! I haven't an original SMS to hand to test it out on unfortunately.

Mike

Quote

>> I'm not sure. I didn't dump it myself but I have heard some models of the SMS behave this way.
>> (if no cartridge is inserted it jump to the snail game directly)
> But this one jumps to the snail game regardless of whether a cartridge is inserted or not!

Maybe it was hacked then, I don't know :(

It's not specific to your SMS, it's clear, in the code.

Quote

> The US BIOS (bios13.sms) is an odd one though - upon power on it displays the logo then goes straight into the snail maze game, regardless of what you press or what game is inserted. I can't get it to do anything else.

> Is this a bad dump, or has the bios been hacked in some way?

I tend to think it's a bad dump. I spent a great deal of time pouring over the disassembly of the BIOS while trying to get them to work in CHASMS, and well -- the bios13.sms posted simply isn't right. It loads the cartridge-detect routine into memory, but NEVER EXECUTES IT, among other things. And the code for the instructions screen is in there, but it's never accessed. So I'm quite certain that something just isnt right with the dump -- I can't imagine any situation where it would make sense. I finally just romhacked the BIOS to work the way I want it to -- But until I build a devcart of my own I can't figure out the proper way port $3E works (cartridge detect), so I can't create a truly fixed BIOS ROM yet.

- vecna

Quote

> > The US BIOS (bios13.sms) is an odd one though - upon power on it displays the logo then goes straight into the snail maze game, regardless of what you press or what game is inserted. I can't get it to do anything else.

> > Is this a bad dump, or has the bios been hacked in some way?

> I tend to think it's a bad dump. I spent a great deal of time pouring over the disassembly of the BIOS while trying to get them to work in CHASMS, and well -- the bios13.sms posted simply isn't right. It loads the cartridge-detect routine into memory, but NEVER EXECUTES IT, among other things. And the code for the instructions screen is in there, but it's never accessed.

Based on that, I'm -sure- it was a hack. Most likely it was hacked and released so people with an appopriate backup system (the game gear one, or a MGD^2 if you were lucky enough to find/afford one) could play snail race on a system which didn't come with it.

Quote

> Based on that, I'm -sure- it was a hack. Most likely it was hacked and released so people with an appopriate backup system (the game gear one, or a MGD^2 if you were lucky enough to find/afford one) could play snail race on a system which didn't come with it.

Hnmm. Well then, I've created a 'fixed' USA ROM BIOS. This BIOS will not actually properly run in any existing emulator right now, because none of us seem to know how port $3E works yet -- but this should run properly on a Real SMS. I've patched it to call the cartridge-detect routine and if the cart-detect routine returns, it will return to the instruction screen rather than straigh to the snail game -- and if a cart is there, it should load that up, too. My best guess is that this ROM is identical to what you should get with a proper dump.

Mike, I'd be real interested if you could try this out and let me know if it works or not. If it does, then I can confirm I have a pretty good grasp on how the BIOS works, if I can just decypher the damn cart-detect/page-in routine and how port $3E works.

You can get it here: http://chasms.midgetrebellion.com/bios13fixed.sms

- vecna

Quote

> > Based on that, I'm -sure- it was a hack. Most likely it was hacked and released so people with an appopriate backup system (the game gear one, or a MGD^2 if you were lucky enough to find/afford one) could play snail race on a system which didn't come with it.

> Hnmm. Well then, I've created a 'fixed' USA ROM BIOS. This BIOS will not actually properly run in any existing emulator right now, because none of us seem to know how port $3E works yet -- but this should run properly on a Real SMS. I've patched it to call the cartridge-detect routine and if the cart-detect routine returns, it will return to the instruction screen rather than straigh to the snail game -- and if a cart is there, it should load that up, too. My best guess is that this ROM is identical to what you should get with a proper dump.

> Mike, I'd be real interested if you could try this out and let me know if it works or not. If it does, then I can confirm I have a pretty good grasp on how the BIOS works, if I can just decypher the damn cart-detect/page-in routine and how port $3E works.

Your patch has done the trick, Vecna - the BIOS now behaves exactly as it should! With no cart present, it does go to the instruction screen rather than the snail game - and any cartridge inserted loads just fine.

I also tried it out in my hacked cart to test it on the GG and MD, and it works exactly as it does on a SMS with no cart inserted, i.e. instruction screen/snail game.

Trying this cart on the SMS (with Japanese BIOS) simply caused the logo sequence to cycle over and over.

Mike

Quote

> Your patch has done the trick, Vecna - the BIOS now behaves exactly as it should! With no cart present, it does go to the instruction screen rather than the snail game - and any cartridge inserted loads just fine.

So you're putting this bios rom in an alex kidd sms2, right?

here's a notion: Try this bios with tetracycline (aka my tetris) and let me know what you get. I suspect you may get a 'Software Error' (rarely happens but I have seen it on my SMS 1) since there's no checksum or 'TMR SEGA' code (YET!).

P.S. You are my hero. As much as I like to tinker with low level z80 code and stuff, I have -no- talent for hardware projects like what you've put together.

Quote

> So you're putting this bios rom in an alex kidd sms2, right?

> here's a notion: Try this bios with tetracycline (aka my tetris) and let me know what you get. I suspect you may get a 'Software Error' (rarely happens but I have seen it on my SMS 1) since there's no checksum or 'TMR SEGA' code (YET!).

Well... with the Japanese BIOS installed, the game loads and plays OK. With both the Alex Kidd and original US BIOS, it's as if no cart is inserted - the instruction screen, or Alex Kidd, appears instead.

The only time I've seen "Software Error", incidentally, was when I tried to play the Japanese "Alex Kidd in Miracle World" with the Alex Kidd BIOS in place. (Don't ask why!)

Quote

> P.S. You are my hero. As much as I like to tinker with low level z80 code and stuff, I have -no- talent for hardware projects like what you've put together.

Who me? *blush* :) Anyway, I'm hopeless at coding, and anyone who can program stuff for the SMS gets my utmost admiration!

Cheers,
Mike

Author	Message
Mike G Joined: 21 Apr 2000 Posts: 598 Location: Newcastle upon Tyne, England	BIOS weirdness Posted: Wed May 31, 2000 9:22 am
	I desoldered the BIOS from my SMS-2 and fitted a socket so I could try different BIOS versions. The Japanese BIOS (posted by Zoop earlier) works fine, plays all games as expected. Funnily enough I thought fitting a Japanese BIOS would put the SMS into Japanese text mode, but evidently not! I still have no clue how a language switch might be implemented. The US BIOS (bios13.sms) is an odd one though - upon power on it displays the logo then goes straight into the snail maze game, regardless of what you press or what game is inserted. I can't get it to do anything else. Is this a bad dump, or has the bios been hacked in some way? Mike

Zoop Joined: 24 Jun 1999 Posts: 1732 Location: Paris, France	Posted: Wed May 31, 2000 10:46 am
	Quote > Is this a bad dump, or has the bios been hacked in some way? I'm not sure. I didn't dump it myself but I have heard some models of the SMS behave this way. (if no cartridge is inserted it jump to the snail game directly)

Mike G Joined: 21 Apr 2000 Posts: 598 Location: Newcastle upon Tyne, England	Posted: Wed May 31, 2000 8:04 pm
	Quote > > Is this a bad dump, or has the bios been hacked in some way? > I'm not sure. I didn't dump it myself but I have heard some models of the SMS behave this way. > (if no cartridge is inserted it jump to the snail game directly) But this one jumps to the snail game regardless of whether a cartridge is inserted or not! It may be to do with the fact that I'm using it on a Master System II - funny that the Japanese one should work fine though! I haven't an original SMS to hand to test it out on unfortunately. Mike

Zoop Joined: 24 Jun 1999 Posts: 1732 Location: Paris, France	Posted: Wed May 31, 2000 9:27 pm
	Quote >> I'm not sure. I didn't dump it myself but I have heard some models of the SMS behave this way. >> (if no cartridge is inserted it jump to the snail game directly) > But this one jumps to the snail game regardless of whether a cartridge is inserted or not! Maybe it was hacked then, I don't know :( It's not specific to your SMS, it's clear, in the code.

vecna Guest	Posted: Wed May 31, 2000 9:37 pm
vecna Guest	Quote > The US BIOS (bios13.sms) is an odd one though - upon power on it displays the logo then goes straight into the snail maze game, regardless of what you press or what game is inserted. I can't get it to do anything else. > Is this a bad dump, or has the bios been hacked in some way? I tend to think it's a bad dump. I spent a great deal of time pouring over the disassembly of the BIOS while trying to get them to work in CHASMS, and well -- the bios13.sms posted simply isn't right. It loads the cartridge-detect routine into memory, but NEVER EXECUTES IT, among other things. And the code for the instructions screen is in there, but it's never accessed. So I'm quite certain that something just isnt right with the dump -- I can't imagine any situation where it would make sense. I finally just romhacked the BIOS to work the way I want it to -- But until I build a devcart of my own I can't figure out the proper way port $3E works (cartridge detect), so I can't create a truly fixed BIOS ROM yet. - vecna

Heliophobe Site Admin Joined: 25 Oct 1999 Posts: 2029 Location: Monterey, California	Posted: Thu Jun 01, 2000 5:24 pm
	Quote > > The US BIOS (bios13.sms) is an odd one though - upon power on it displays the logo then goes straight into the snail maze game, regardless of what you press or what game is inserted. I can't get it to do anything else. > > Is this a bad dump, or has the bios been hacked in some way? > I tend to think it's a bad dump. I spent a great deal of time pouring over the disassembly of the BIOS while trying to get them to work in CHASMS, and well -- the bios13.sms posted simply isn't right. It loads the cartridge-detect routine into memory, but NEVER EXECUTES IT, among other things. And the code for the instructions screen is in there, but it's never accessed. Based on that, I'm -sure- it was a hack. Most likely it was hacked and released so people with an appopriate backup system (the game gear one, or a MGD^2 if you were lucky enough to find/afford one) could play snail race on a system which didn't come with it.

vecna Guest	Posted: Thu Jun 01, 2000 7:08 pm
vecna Guest	Quote > Based on that, I'm -sure- it was a hack. Most likely it was hacked and released so people with an appopriate backup system (the game gear one, or a MGD^2 if you were lucky enough to find/afford one) could play snail race on a system which didn't come with it. Hnmm. Well then, I've created a 'fixed' USA ROM BIOS. This BIOS will not actually properly run in any existing emulator right now, because none of us seem to know how port $3E works yet -- but this should run properly on a Real SMS. I've patched it to call the cartridge-detect routine and if the cart-detect routine returns, it will return to the instruction screen rather than straigh to the snail game -- and if a cart is there, it should load that up, too. My best guess is that this ROM is identical to what you should get with a proper dump. Mike, I'd be real interested if you could try this out and let me know if it works or not. If it does, then I can confirm I have a pretty good grasp on how the BIOS works, if I can just decypher the damn cart-detect/page-in routine and how port $3E works. You can get it here: http://chasms.midgetrebellion.com/bios13fixed.sms - vecna

Mike G Joined: 21 Apr 2000 Posts: 598 Location: Newcastle upon Tyne, England	Posted: Thu Jun 01, 2000 9:58 pm
	Quote > > Based on that, I'm -sure- it was a hack. Most likely it was hacked and released so people with an appopriate backup system (the game gear one, or a MGD^2 if you were lucky enough to find/afford one) could play snail race on a system which didn't come with it. > Hnmm. Well then, I've created a 'fixed' USA ROM BIOS. This BIOS will not actually properly run in any existing emulator right now, because none of us seem to know how port $3E works yet -- but this should run properly on a Real SMS. I've patched it to call the cartridge-detect routine and if the cart-detect routine returns, it will return to the instruction screen rather than straigh to the snail game -- and if a cart is there, it should load that up, too. My best guess is that this ROM is identical to what you should get with a proper dump. > Mike, I'd be real interested if you could try this out and let me know if it works or not. If it does, then I can confirm I have a pretty good grasp on how the BIOS works, if I can just decypher the damn cart-detect/page-in routine and how port $3E works. Your patch has done the trick, Vecna - the BIOS now behaves exactly as it should! With no cart present, it does go to the instruction screen rather than the snail game - and any cartridge inserted loads just fine. I also tried it out in my hacked cart to test it on the GG and MD, and it works exactly as it does on a SMS with no cart inserted, i.e. instruction screen/snail game. Trying this cart on the SMS (with Japanese BIOS) simply caused the logo sequence to cycle over and over. Mike

Heliophobe Site Admin Joined: 25 Oct 1999 Posts: 2029 Location: Monterey, California	Posted: Fri Jun 02, 2000 4:41 pm
	Quote > Your patch has done the trick, Vecna - the BIOS now behaves exactly as it should! With no cart present, it does go to the instruction screen rather than the snail game - and any cartridge inserted loads just fine. So you're putting this bios rom in an alex kidd sms2, right? here's a notion: Try this bios with tetracycline (aka my tetris) and let me know what you get. I suspect you may get a 'Software Error' (rarely happens but I have seen it on my SMS 1) since there's no checksum or 'TMR SEGA' code (YET!). P.S. You are my hero. As much as I like to tinker with low level z80 code and stuff, I have -no- talent for hardware projects like what you've put together.

Mike G Joined: 21 Apr 2000 Posts: 598 Location: Newcastle upon Tyne, England	Posted: Sat Jun 03, 2000 1:33 pm
	Quote > So you're putting this bios rom in an alex kidd sms2, right? > here's a notion: Try this bios with tetracycline (aka my tetris) and let me know what you get. I suspect you may get a 'Software Error' (rarely happens but I have seen it on my SMS 1) since there's no checksum or 'TMR SEGA' code (YET!). Well... with the Japanese BIOS installed, the game loads and plays OK. With both the Alex Kidd and original US BIOS, it's as if no cart is inserted - the instruction screen, or Alex Kidd, appears instead. The only time I've seen "Software Error", incidentally, was when I tried to play the Japanese "Alex Kidd in Miracle World" with the Alex Kidd BIOS in place. (Don't ask why!) Quote > P.S. You are my hero. As much as I like to tinker with low level z80 code and stuff, I have -no- talent for hardware projects like what you've put together. Who me? blush :) Anyway, I'm hopeless at coding, and anyone who can program stuff for the SMS gets my utmost admiration! Cheers, Mike

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