Dreamcast VGA adaptor - possible to add a 15khz/31khz switch?

[eastbayarb]

I have a Dreamcast with a VGA adaptor and my monitor supports 15khz and 31khz. As you probably know, some games don't support 31khz VGA (even with the supposed trick that forces 31khz), so I was wondering if it was possible to add a switch that can let you choose between 15khz and 31khz?

thanks

[ken_cinder]

Yes, just put a switch on the line for pin 6 or 7 to open or close the circuit, though I'm not sure which one as I don't understand what these "two different kinds of RGB" even means. With the circuit open it will output 15khz, with it closed you'll have 31khz.

Read this - http://www.gamesx.com/wiki/doku.php?id=av:dreamcastav

[Link83]

Yes, if you keep one pin grounded (I think its pin 7) you get 15kHz RGB, and then if you ground both pins 6 and 7 you get 31kHz RGBHV.

However, (some one please correct me if im wrong) I think I have read that in 15kHz RGB H-Sync and V-Sync signals are disabled, so you would need to use a sync separating circuit on the C-Sync line to replace them. Also you may need to use a multiple throw switch in order to disconnect these 'extra' syncs when using 31kHz 

[ken_cinder]

Yes, if you keep one pin grounded (I think its pin 7) you get 15kHz RGB, and then if you ground both pins 6 and 7 you get 31kHz RGBHV.

However, (some one please correct me if im wrong) I think I have read that in 15kHz RGB H-Sync and V-Sync signals are disabled, so you would need to use a sync separating circuit on the C-Sync line to replace them. Also you may need to use a multiple throw switch in order to disconnect these 'extra' syncs when using 31kHz 

Depends on his display. My LCD TVs accept 15/31 over VGA and one of them only requires H-Sync, feeding it V-Sync changes nothing and the other requires H+V tied together on the H line......no separation required in the case of either TV.

This is pretty much one of those "Try it and see" things if you have no schematics/docs on the display in question.

[Blaine]

Yes, if you keep one pin grounded (I think its pin 7) you get 15kHz RGB, and then if you ground both pins 6 and 7 you get 31kHz RGBHV.

However, (some one please correct me if im wrong) I think I have read that in 15kHz RGB H-Sync and V-Sync signals are disabled, so you would need to use a sync separating circuit on the C-Sync line to replace them. Also you may need to use a multiple throw switch in order to disconnect these 'extra' syncs when using 31kHz 

I'm 90% sure it is pin 7 and 99% sure that it's composite sync.

15khz RGB is just Euroscart (which you have on the Dreamcast).

LM1881 circuit to strip sync from the composite video and you're bangin'.

http://gamesx.com/wiki/doku.php?id=av:lm1881

[ken_cinder]

Sorry I re-read what my silly butt posted earlier. My displays will accept COMPOSITE sync over those pins, I've hooked my arcade boards up to both displays over VGA with no problems.

I think I need a posting break, I've probably made over 1000 posts in the last week or so on all the forums I visit and I'm starting to type without thinking about what I actually say.

[Link83]

I think that you could use either the Composite Video (Pin 13) or Composite Sync (Pin 10) as when the Dreamcast is in RGB mode it switches Composite Video on Pin 13 into Composite Sync anyway - thats why you cant get a Composite picture from the Official RGB Scart cable as the Dreamcast is only sending C-Sync once Pin 7 is grounded (I imagine this means theres two Composite Sync pins in 15kHz RGB mode)

I am not sure if there any place that has all the 'effects' of the mode pins fully described (eg what signals get enabled/disabled with each RGB mode) Perhaps if someone knows they could add it to the Wiki?:-
http://gamesx.com/wiki/doku.php?id=av:dreamcastav

In 90% sure that in the Official RGB Scart cable Pin 7 is grounded, not Pin 6. (If anyones interested I will double check)

I have always been curious to know what the 'alternate' 15kHz RGB mode with Pin 6 grounded instead actually does. I read in one old thread that some games that wouldnt usually work in 15kHz RGB with Pin 7 grounded actually work with in 15kHz RGB with Pin 6 gounded instead  (I have even read that some third party Dreamcast Scart cables actually have Pin 6 grounded instead of Pin 7!)

[Paper]

Allow me to give my two cents, and as far as I'm concerned final and complete solution, of this "two types of RGB" Dreamcast dilemma.

The Dreamcast supports one type of 15kHz RGB which can be enabled in two ways.

What lead to the confusion of thinking there are two types of RGB is because some games only work in "one" mode, while others work in the "other". It has to be added that there are also two games working in neither (Giga Wing and Timestalkers, according to an older thread on this forum).

So, what is the cause of this?

The core idea is RGB protection related to importing. RGB protection means disabling RGB output on a non European title to prohibit importing.

a) Enabling RGB output via pin 6 or 7 differentiates between (RGB) region Japan or Europe. This way American games can be RGB protected to not work in Europe, but do work in Japan.

b) Sega's own files were unclear about this function leading some American game programmers to disable RGB output by checking only for pin 7 and others for only pin 6 while thinking this would cause a complete removal of RGB output. The smart few checked for both.

[Endymion]

Sounds like a reasonable enough position. I'll leave it at that as I have no exact knowledge of Sega's decree for implementation. However, is there really a reason to do this with each line? (6 and 7) I recently added a switch to my VGA box at line 6 and it works like a treat, Bangai-oh in RGB, Dino Crisis with working movies, etc. etc. But I really cannot bring myself to install a second switch for line 7 without anything more concrete. All the other games that the 6-switch do not enable are either working in VGA mode (6 & 7 grounded), or can be fooled into doing either RGB or VGA by using the PC/TV switch.

I don't think I've ever seen an answer as to which games might work with pin 7 switched and not pin 6. Anyone?

[Link83]

Sounds like a plausible explanation, but when you said:-

a) Enabling RGB output via pin 6 or 7 differentiates between (RGB) region Japan or Europe. This way American games can be RGB protected to not work in Europe, but do work in Japan.

I dont believe Sega (or third parties) ever released a Japanese RGB-21 'Scart' cable, which would kind of rule out the 'RGB region protection' idea, so once again were stuck with why there were two different ways to enable the same 15kHz RGB mode. (Perhaps it was just a feature of the video chip?)

I have looked through the Katana SDK and the 15kHz RGB Scart option seems to have been added as abit of an afterthought. When compiling a game/burning a GD-R there is no specific option to enable Scart cable support, as there is for the VGA box and all other accessories. The game must have specific lines of code in the development library in order to enable 15kHz RGB/support the Scart cable, and although it appears that this was already enabled by default in the standard development software, there is also mention that it was possible to accidentally 'break' Scart support, and Sega even gave instructions on how to fix the necessary lines of code.

I can try and dig up some pictures about Scart support in Sega's SDK documentation if anyones interested? (If im allowed to post them that is? As they are from the official development software)

[Paper]

I didn't know that (regarding the lack of official Japanese SCART cable). A quick search draws indeed blank on it.

I came up with the RGB protection idea mainly as concerned with the USA to EUR importing, because as far as I know there are no EURO titles not working with RGB. The Dreamcast I bought, around the time it came out, even came with a SCART RGB cable packed in.

Curious how there is indeed plenty of reason the coders might have made mistakes in this area. We might all be looking for logic and reason were there is none.

I'd love to see those pictures. If not here, somewhere else.

Edymion:

There is a list of those games on this forum. I came across it while searching here before I posted.

http://nfggames.com/forum2/index.php?&topic=2504.0

Another interesting thing is that there are some homebrewn games in that list. I wonder what light the coders of those can shed on this.

[Link83]

Paper, I guess you are from France then? As I believe only French Dreamcasts came with an RGB Scart cable as standard. In the UK we got rubbish RF cables in the box 

btw, in the thread you linked to the OP seems to have made a slight misunderstanding(?) Pin 7 is the default pin that is grounded on the official Dreamcast Scart cable, not Pin 6. As such all those games he listed will work using a standard/official scart cable (I have even played quite a few on original disks over an official RGB Scart cable) The question should be which games dont work with pin 7 grounded. Heres a list of the few US/JPN Dreamcast games I have read of which dont work with an RGB Scart cable:-

Timestalkers
Giga Wing
Street Fighter Zero 3
Street Fighter II X
Vampire Chronicles
Eternal Arcadia

What would be interesting is if the few games that dont work with pin 7 grounded, do work with pin 6 grounded instead.

Another interesting thing to test would be to see if these few games that wont output in 15kHz RGB (Scart) can be 'tricked' into 15kHz RGB much like the VGA switch trick, eg. boot the game with no pins grounded, and then after the disks gets up to speed (ip.bin file has already been read) you flick a switch and ground Pin 7 (or pin 6) and see if you can 'trick' these games into 15kHz RGB.  Sometime I might even see if I can add a switch to one of my Scart cables (Disconnecting pin 7 from ground, and putting a switch in between)

----------------------------------------------------------------------------------------------------------------------------------

Im not sure im if allowed to post these SDK pics (Although I cant see why Sega would still care!) but if i'm not supposed to post them someone please let me know and I will remove them immediately.

Heres one pic from the 'Sega of Europe software standards' slides which shows that RGB support was a requirement for PAL Dreamcast software:-


Heres a small quote from a 'PAL modes' document' (The full thing is quite an interesting read, and shows that Sega really cared about European gamers):-

NOTE: SCART Compatibility for European Software

SHINOBI USERS: To ensure compatibility with RGB cables, which is completely essential for European software, please switch to the new syCblCheck()shinobi function.   Correct implementation of this is shown below in the Extended PAL mode section.

and heres a small sequence from the 'Shinobi Sega Library' slides which shows the old and new coding required to identify the cable type connected to the console:-


The last image mentions that there is 'no specific return for RGB'  so I dont even think the software can tell that an RGB cable is connected.

The Dreamcast Dev box uses dip switches to set the video mode (basically grounding pins 6 and/or 7) and the SDK 'Getting Started' guide gives this information:-

Note: The left two DIP switches determine the standard video output
mode reported to software:

Switch 1  Switch 2  Meaning

OFF       OFF       Stereo AV cable, S-video, or RF output
ON        OFF       RGB (NTSC or PAL)
OFF       ON        Undefined
ON        ON        VGA cable

As you can see, the 'second' RGB mode is set as 'Undefined' by Sega themselves (Assuming 'Switch 2' = Pin 6)

Theres quite abit more info about 15kHz RGB in the SDK but im afraid I havent got time to find all the little tidbits scattered around at the moment 

Hope that someone finds this interesting! 

[Tiido Priimägi]

The H, V and C sync are all useful when in RGB mode (this includes both 15 and 31KHz modes). The Undefined mode is usually interpreted as 15KHz RGB mode, but some games like Bubble Bobble will go into S-vid/composhit mode with that setting instead of RGB.

[Link83]

The H, V and C sync are all useful when in RGB mode (this includes both 15 and 31KHz modes). The Undefined mode is usually interpreted as 15KHz RGB mode, but some games like Bubble Bobble will go into S-vid/composhit mode with that setting instead of RGB.

Really?! H, V and C-Sync are all active in both 15kHz and 31kHz RGB? Thats quite surprising, because if thats the case why does this mod require a sync combining circuit?:-
http://gamesx.com/wiki/doku.php?id=av:dreamcast_480i-480p_scart_cable

Something I have been wondering about recently is if the Composite Video pin is still active in either RGB mode, or is it totally disabled? Or does it just switch into a C-Sync signal instead? (Making two active C-Sync pins) There seems to be alot of confusion about what pins are active in any given mode, so I recently started to compile a chart at the bottom of the Wiki page:-
http://gamesx.com/wiki/doku.php?id=av:dreamcastav

If somebody with an oscilloscope would like to help me determine which pins still produce a valid signal in each mode to help fill in the blanks in the chart (and correct any that may be wrong) it would be very much appreciated 

[Endymion]

Edymion:

There is a list of those games on this forum. I came across it while searching here before I posted.

http://nfggames.com/forum2/index.php?&topic=2504.0

Another interesting thing is that there are some homebrewn games in that list. I wonder what light the coders of those can shed on this.

Wow, thanks for that. I don't know how I ever missed it. It looks like all of the games in that list either work in VGA natively or via the PC/TV switch though. I think I'll not bother with a pin 7 switch.

[Tiido Priimägi]

Really?! H, V and C-Sync are all active in both 15kHz and 31kHz RGB? Thats quite surprising, because if thats the case why does this mod require a sync combining circuit?:-
http://gamesx.com/wiki/doku.php?id=av:dreamcast_480i-480p_scart_cable

Something I have been wondering about recently is if the Composite Video pin is still active in either RGB mode, or is it totally disabled? Or does it just switch into a C-Sync signal instead? (Making two active C-Sync pins) There seems to be alot of confusion about what pins are active in any given mode, so I recently started to compile a chart at the bottom of the Wiki page:-
http://gamesx.com/wiki/doku.php?id=av:dreamcastav

If somebody with an oscilloscope would like to help me determine which pins still produce a valid signal in each mode to help fill in the blanks in the chart (and correct any that may be wrong) it would be very much appreciated 

Actually now thinking, I don't know if Csync is available in 31KHz, but H and V sync most definitely are in 15KHz, I have my own sync joining circuit in my DC for slightly better sync.... I see no reason whatsoever for Csync not to be active in 31KHz mode... must check next time I open my DC.
The S-vid and Composite signals seem to be non active in RGB mode.

[Paper]

What would be interesting is if the few games that dont work with pin 7 grounded, do work with pin 6 grounded instead.

Yes, actually that brought me here.

Skies of Arcadia (USA) does not work with pin 7 grounded, but it does work with pin 6 grounded. Again we are talking about USA games.

Wetrix +, Elemental Gimmick Gear and Gunbird 2 (all USA) eventhough not tested by me are likely to work with pin 6 as I know they do not work with pin 7 grounded and they are not on the above posted list.

Judging from your info it looks like PAL games were extensively tested on the RGB front, but the other regions weren't; leading to broken or absent support for RGB.

[Link83]

Thanks, so a more complete list of RGB incompatible games (as standard) with regions added would be:-

Wetrix+ (USA/JPN)
Gunbird 2 (USA/JPN)
Timestalkers (USA/JPN)
Giga Wing (USA/JPN)
Elemental Gimmick Gear (USA/JPN)
Skies of Arcadia (USA) / Eternal Arcadia (JPN)
Street Fighter Alpha 3 (USA) / Street Fighter Zero 3 (JPN)
Street Fighter II X for Matching Service (JPN)
Vampire Chronicle for Matching Service (JPN)
Touken Retsuden 4 (JPN)
Pop 'n Music (JPN)
Pop 'n Music 2 (JPN)
Pop 'n Music 3 Append Disk (JPN)
Pop 'n Music 4 Append Disk (JPN)
(Information compiled from user reports, not all regions have been tested)

Does that seem right?

One thing that is abit of a shame is that whilst adding RGB support to the PAL version of Skies of Arcadia they seemingly forgot to 're-tick the box' to enable VGA support, meaning that the PAL version no longer supports VGA 

<EDIT> Found out theres alot more games than those I have listed, some mentioned here:-
http://ntsc-uk.domino.org/showthread.php?t=11538
and some more mentioned 3/4 of the way down this page as having RGB Fix's available (Although RGB could just be broken because the games were copied):-
http://www.snesorama.us/board/showthread.php?t=29432

[Paper]

You can see the same confusion in the thread from NTSC-UK.

I have a feeling some people there had cables with pin 6 grounded and others with pin 7 leading to endless confusion and having them go as far to say some people couldn't see the difference between a cdr or the real thing, or RGB and composite (yeah, right).

Yeah, and they didn't add 60hz support to Skies or Arcadia PAL either. Do you know perhaps if it can be forced into 60hz by using the region changer to patch the bios? I can't say I like the small changes between the PAL and US version.

[Endymion]

All that does is change the console's region, it will not alter the content in your game.

[Link83]

All that does is change the console's region, it will not alter the content in your game.

Actually the region changer mod can also switch the consoles default video mode to NTSC /60Hz aswell as changing the region  It doesnt change the game content, but it does force most 50Hz only games into 60Hz (Although I havent tried it with Skies of Arcadia yet)

[Paper]

What he said.

More interestingly though it is able to switch the region to PAL, but the video output to NTSC, at the same time, making even PAL games lacking 60hz (such as Grandia 2) and impossible to force into 60hz otherwise play in 60hz.

In the case of Grandia 2 though timing problems turn up, I wonder how SOA take

[Tiido Priimägi]

And Csync is available in all RGB modes.

By RGB incompatible is meant that neither mode won't work or only VGA does not work ?

[Link83]

Yeah, and they didn't add 60hz support to Skies or Arcadia PAL either. Do you know perhaps if it can be forced into 60hz by using the region changer to patch the bios? I can't say I like the small changes between the PAL and US version.

I have just tested PAL Skies of Arcadia (original) on a PAL Dreamcast with the video mode set to NTSC 60Hz using Region Changer, and unfortunately once the Sega logo comes up it seems to switch into 50Hz  Guess the NTSC version (without RGB Scart support as standard) is the only way to go for 60Hz and VGA goodness...

Out of curiosity what are the small changes between the PAL and US versions, apart from the available video modes?

And Csync is available in all RGB modes.

By RGB incompatible is meant that neither mode won't work or only VGA does not work ?

So do you mind if I ask if its now 'definite' that H, V and C-Sync are all active in both 15kHz and 31kHz RGB modes? If so I guess there really wasnt any need for that H&V-Sync combining circuit mod I linked to in my earlier post? 

I would also be very interested to know if the Composite Video and S-Video pins are at all active in either RGB mode. I have read that they are both are disabled in 31kHz RGB mode, but I wonder if they are still active in 15Khz RGB mode? (Im guessing they are still disabled, but it would be nice to confirm it for sure) Im also curious if they are totally disabled, or for instance does the Composite Video pin become an extra C-Sync?

'RGB incompatible' in this instance just means that it wont work in 15kHz RGB mode (RGB SCART) The listed games could still work in 31kHz RGB mode (VGA) as the two dont seem settings dont seem to be related/connected. Many games that dont support 15kHz RGB still support 31kHz RGB, or visa-versa

[Paper]

Names and dialog. It was softened up here and there.

There is an enemy for example consisting of a man with a bug on his head, apparently controlling him. In the Euro version (and I guess the Japanese version) it is called "Dementis". In the USA version it is called Mindripper or something with similar lameness.

It is the same thing with Skies of Arcadia Legends on the Gamecube (but that port is so completely horrible!).

Actually the Euro version is softened up too compared to the Japanese version. In the original game people drink alcohol and not the "juice" loqua, among other things.

http://hg101.classicgaming.gamespy.com/skiesofarcadia/skiesofarcadia.htm has some more info (if little).

On the Sync topic. In the RGB cable it is the C-Sync pin that is used and not the composite video pin (at least in my cable, maybe this pin differs in use too).

[RGB32E]

The official Sega Dreamcast Scart Cable (model MK-5516-50):
-Uses mode select pin 7
-Sync connection is from pin 10 (CSYNC)
-Composite video pin is not used, wired, nada (no pin on connector position 13)
Looks like a fun waste of time testing out the games I have! 

Crappy pix: