Author Topic: TEOS replacement OS for the TurboEverDrive v2  (Read 1674 times)

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Offline elmer

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TEOS replacement OS for the TurboEverDrive v2
« on: January 27, 2021, 04:44 AM »
Here is the latest public beta of TEOS.

It fixes problems with the following games ...

* Tower of Druaga
* Space Harrier
* Shiryou Sensen
* Out Live
* Benkei Gaiden
* Gekisha Boy
* Night Creatures


TEOS Beta5

Just extract the archive, and copy the files to the root of your Turbo EverDrive's SD card.

In particular ... the contents of the /TBED/ directory *must* go in that directory.

If you have already got some of those files in your /TBED/ directory, then you must have been running an earlier beta version ... please do NOT overwrite those files, or you will lose your BRAM saves.

While you *can* theoretically rename teos.pce to OS.PCE and put it in your /TBED/ directory, and it should work, I do NOT recommend doing that at this point. This is a beta test version of TEOS, and it is far safer to just run it like a normal cart from Krikzz's OS ... you have been warned!

If you find any problems, then it would be better to report them in the "Homebrew Development" section of the "PC Engine Software Bible forum", rather than cluttering up KRIKzz's forum here.

Developers ... please note that TEOS does not currently support uploading HuCard images through the Turbo EverDrive's USB connection!
« Last Edit: January 27, 2021, 03:27 PM by elmer »

Offline phoenixdownita

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Offline elmer

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Re: TEOS replacement OS for the TurboEverDrive v2
« Reply #2 on: January 27, 2021, 03:29 PM »
Fixed link

Whoops, thanks! :-)

I've fixed the link in the top message now.

Offline nuu

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Re: TEOS replacement OS for the TurboEverDrive v2
« Reply #3 on: January 27, 2021, 06:11 PM »
It fixes problems with the following games ...

* Tower of Druaga
* Space Harrier
* Shiryou Sensen
* Out Live
* Benkei Gaiden
* Gekisha Boy
* Night Creatures
Thank you for making this elmer!
I have a question. Why didn't these games work on the original OS? I thought most games (not counting Street Fighter II', Populous, System Cards etc) worked the same way as far as flashcarts like the TED are concerned?

Offline elmer

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Re: TEOS replacement OS for the TurboEverDrive v2
« Reply #4 on: January 27, 2021, 09:37 PM »
I have a question. Why didn't these games work on the original OS? I thought most games (not counting Street Fighter II', Populous, System Cards etc) worked the same way as far as flashcarts like the TED are concerned?

All of the games listed above (except for "Tower of Druaga") fail to reset the VCE clock-speed register when they start up, and they just assume that it is "0" (i.e. a 5MHz pixel clock for the VDC).

In earlier versions of TEOS, I did not reset that register to "0" before starting up the HuCard, and so those games display 4-screens-in-one ... which is obviously wrong.

Now I do reset all VDC values to "safe" settings before starting a HuCard.

KRIKzz's OS doesn't have this problem with those games, so it is pretty obvious that he is reseting the VCE speed before running a HuCard ... which it turns out is actually important for some games.


It is just like the problem with "Populous" on KRIKzz's OS ... I must be setting/clearing some hardware register that he isn't, which is why the game runs fine on TEOS, but has graphical glitches on KRIKss's OS.


The issue with "Tower of Druaga" is that when it is started, it will crash if it gets to a certain point in the game code before it gets its first VBLANK interrupt.  This is a horrible bug in the game code, and it *seems* as though KRIKzz's OS *may* have just been lucky in that his startup condition is such that the game gets the interrupt that it needs in time.

Earlier versions of TEOS start the HuCard image just a few scanlines after a VBLANK ... which allows this game bug to occur, and so the game crashes.

TEOS has been changed to wait until the screen has actually begun to display before starting the HuCard image, which is enough difference in time to avoid triggering that bug, and so "Tower of Druaga" now works on TEOS. :-)


So "yes", all games on the TED2 basically run with the same startup conditions, but they aren't *exactly* the same startup conditions that you get when you turn on your PCE's power, because either KRIKzz's OS or TEOS is run first.

It turns out that some games are just a little more sensitive to the exact startup conditions than others. ;-)

Offline nuu

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Re: TEOS replacement OS for the TurboEverDrive v2
« Reply #5 on: January 28, 2021, 01:44 PM »
Ok it's all just initialization errors, I understand. This problem exists more or less for all flashcarts that loads roms after selecting them on a menu that's running on the console itself. Thanks for explaining.