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Tempest

Skip Startup Screen BIOS Game Compatiblity

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I've been thinking about trying that BIOS hack that allows you to skip the startup screen if you push a button (which is how it should have been from the beginning if you ask me).  However I seem to recall some people saying that certain games don't work with it because it's not the 100% original BIOS.  Does anyone have a list of games that had issues?  Does anyone know if they've been patched?

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Posted (edited)

The game that has issues with the fire skip BIOS is Sewer Sam.  ChildOfCv documented what the problem was here and highlighted that the fire skip BIOS may cause issues with other timing-critical games.  I remember a few others saying that there was possibly another affected game but I can't recall if that is correct or not.  I also summarise the various BIOS alternatives here.

 

Because of this issue I now use, and recommend, a BIOS that simply reduces the startup screen duration (my choice being that of what CBS Electronics chose for PAL systems, i.e. 3.3 seconds instead of the 12.65 second NTSC default).  Here's more info about that.

 

 

Edited by Ikrananka
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So using a BIOS that reduces the time doesn't break games but the skip BIOS does?  That's interesting.  I'm ok with waiting 3 seconds or so, that's fine.

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6 minutes ago, Tempest said:

So using a BIOS that reduces the time doesn't break games but the skip BIOS does?

Yes, that's the case.  The BIOS was designed to have a configurable startup duration so it's in effect an original feature of the design.  However, the fire skip BIOS is a hack that can have unintended consequences with some games.

 

Here's my 3.3 second delay NTSC BIOS if you need it.

 

 

ColecoVision BIOS OS7 (2019)(Ikrananka)(NTSC)[3.3s Title Delay].rom.zip

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5 hours ago, Tempest said:

So using a BIOS that reduces the time doesn't break games but the skip BIOS does?  That's interesting.  I'm ok with waiting 3 seconds or so, that's fine.

The issue is that Sewer Sam (and possibly other games) call into unofficial parts of the BIOS code.  Since they are unofficial and undocumented, the idea is that future BIOS revisions may change them as needed, invalidating any behavior you attempted to use.  But SS did it anyway.  The fire-skip modification is an unofficial mod to the BIOS, but at least it doesn't affect the documented functions.  So only the "bad" games might be affected by it.

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Thanks for refreshing my memory on this subject. Good to know about the fire/skip BIOs and it's minor incompatibilities, which I totally forgot about. That's what I currently have in my main rig, but I'll be changing that out for the 3.3 sec one sometime (Thanks for uploading that BTW!). :)

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Also the 3.3 sec delay BIOS is what Console5 is now selling to replace the previous no delay they used to sell. I have one of these newer ones but haven't installed it into my CV yet. One game I had nothing but issues was was the initial release of Risky Rick. The game flat our refused to start up at all with the no delay bios installed. It was the main reason I put the original back into my CV and still use that for the time being. 

 

I'm sure it would work better with the shorter 3.3 sec delay version and I have the ROM for the game now as well so it is more of less a null issue for me at this point.

 

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Posted (edited)
On 6/20/2021 at 2:49 PM, ChildOfCv said:

The issue is that Sewer Sam (and possibly other games) call into unofficial parts of the BIOS code.

This. A long, long time ago (2005-2007) I tried to see just how much I could optimize out of the ROM, so I checked the disassembly of every game I could find to see what parts of the ROM were called. I made a list of those addresses, and marked those in a certain way in my .asm of the ROM, so that I could see in the symbol table dump if they changed. I actually got over 1K of contiguous free space, you could put a small game in there. I may have even made a version with a controller test built in before I got tired of doing Colecovision stuff.

 

So basically the "skip startup screen BIOS" is just someone's sloppy hack that stepped on the wrong bit of code that broke the even sloppier code in a single released game.

 

Here are the notes I put in the source code for my optimized ROM:

; LOCKED ADDRESSES -- THESE *MUST* BE CORRECT OR SOME CARTRIDGES WILL NOT RUN!
;
; In order to allow easy verification, these addresses have labels
; starting with an 'A' and containing the locked address.
;
; These are the important addresses (like vectors), plus a few used by the
; small-time offenders.
;
;    0000    0066    080B    18A3
;    0008    0069    08C0    18D4.
;    0010    006A    143B    18F7*
;    0018    006C    144D    1968
;    0020    01B1*    1463    196B
;    0028    01D5    14B4    1CCA.
;    0030    023B.    14C1    1D43
;    0038    02EE    14C3    1D47
;    003B.    07E8*    15A3    1F61
;            158B*
;
; ...and these are the addresses used by three of the four Interphase
; games, most of which have vectors available.
;
;    0213.    114A*.    1BAA*    1D3E*.
;    025E.    18E9.    1C27.    1D57.
;    027F.    1979*.    1C4F*    1D5A.
;    0300.    1B1D*.    1C82*.    1D60*.
;    1105*    1BA3.    1D01*.    1D66*.
;
; These two were called from Boulder Dash, but the call instructions
; themselves may be unreachable from the rest of the game.
;
;    01C1*    026A*
;
; Any address with a '*' is only referenced by ONE game that I can find.
; Note that Interphase games account for 11 out of 15 of these.  Any address
; with a '.' has a vector available.  Note also that all but two Interphase-
; only addresses (18 of 20) have vectors!  Oh the humanity!
;
; These are in the "OS7SYM" file which was provided to Adam programmers:
;
;FREQ_SWEEP          EQU     000FCH !
;ATN_SWEEP           EQU     0012FH !
;DECLSN              EQU     00190H !
;DECMSN              EQU     0019BH !
;MSNTOLSN            EQU     001A6H !

 

 

Also, f*** Interphase.

coleco29.asm ctltest.asm

coleco.h

Edited by Bruce Tomlin
added coleco.h for ctltest.asm
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The Atari 5200 Ultimate SD cartridge has a similar option where you can skip the splash screen before each game.  I found that if this is enabled then Pole Position won't work properly.  The car just won't control at all and goes off to the upper left.  I wonder how many other 5200 games are broken when skipping the splash screen?

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On 7/7/2021 at 7:28 PM, Tempest said:

The Atari 5200 Ultimate SD cartridge has a similar option where you can skip the splash screen before each game.  I found that if this is enabled then Pole Position won't work properly.  The car just won't control at all and goes off to the upper left.  I wonder how many other 5200 games are broken when skipping the splash screen?

See I like those Atari splash screens so I wouldn't disable that myself.

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36 minutes ago, -^CrossBow^- said:

See I like those Atari splash screens so I wouldn't disable that myself.

I do too, it was on by default and I didn't notice. 

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