Dracula Unleashed (U) reboots to BIOS screen

[Former user]

Original issue 328 created by theothermii on 2013-03-01T01:37:57.000Z:

What steps will reproduce the problem?
1. Use BIOS 2 for US consoles (haven't test BIOS 1)
2. Load Dracula Unleashed (U) rom (tried many different sources)
3. Rom is on USB 2 device, BIOS is on SD card

*Dracula Unleashed (E) using BIOS 2 for European consoles works fine.

What is the expected output? What do you see instead?
I expect the game to continue after the first screen that says Sega. Instead, it reboots to the BIOS screen

What version of the emulator are you using (official, SVN revision,...)?
1.7.3 (IOS 58), downloaded using Homebrew Browser

Please provide any additional information below (Emulator settings, Console
setting,...) Tried many different emulator settings arrangements and nothing works. Research on google indicates that some others have had issues loading this rom on PC's and that a "perfect sync" option fixed it, although I was not able to find that option in Genplus-GX. (on a side but related note... is there a way to put all the settings back to default easily? Since I've been mucking with them, I'm not sure where they were to begin with)

[Former user]

Comment # 1 originally posted by ekeeke31 on 2013-03-01T16:02:53.000Z:

Genesis Plus GX does not have a "perfect sync" option because it does it by default, although not exactly the same as in other emus ( it is more optimized here).

I will look at it when I have some time, i am pretty sure I tested all US releases and this one used to work fine.

[Former user]

Comment # 2 originally posted by ekeeke31 on 2013-03-01T16:12:08.000Z:

You can reset the settings to default by deleting the config.ini file on your sdcard in genplus directory.

[Former user]

Comment # 3 originally posted by ekeeke31 on 2013-03-02T20:07:29.000Z:

It seems compatible with Sega CD BIOS v1.00 and v1.10 (Model 1).
Not sure why it resets with later model BIOS.

[Former user]

Comment # 4 originally posted by ekeeke31 on 2013-04-06T18:45:42.000Z:

It is indeed a synchronization issue between MAIN & SUB CPU.
MAIN-CPU is reading the communication register and if SUB-CPU is not synchronized at that time, it won't update the value in time and MAIN CPU will read an incorrect value.

As a result, MAIN-CPU thinks the shared 2M Word-RAM is available and that it can run code from it, which later cause an exception because the Word-RAM does not hold yet any valid instructions.

It should be fixed in a later revision once I check that the improved synchronization code does not cause any issues in other games or with different BIOS (some games, mainly those using unsafe synchronization methods like this one, are very sensitive to this)

[Former user]

Comment # 5 originally posted by ekeeke31 on 2013-04-19T14:47:05.000Z:

Fixed in r770

I improved the synchronization between the two CPU as well as polling loop detection, and took the time to verify that all existing games boot fine and go to gameplay with either Model 2 or Model 1 BIOS.