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Gravis Ultrasound bug with setup and EMM386

Posted: Wed 27 Dec, 2017 11:59 am
by Fenix77

First of all would like to thank for the hard work done. Its a complete PC emulator and the emulated hardware is greater than any other.

I know this bug may be not top priority now, because a real SB can be used instead SB emulation in the GUS.

I found some strange bugs that locks up the emulator if i run the setup utility of the Gravis Ultrasound (It came with v4.11 of installation disks) ,with EMM386 loaded (of MS-DOS 6.22 version).
The lock ups occurs when the setup test the Sound Blaster and Roland emulation *and* the EMM386 device driver is loaded in config.sys.

The other bug is related to the aforementioned because SBOS (the Sound Blaster Emulator) locks up the system too if EMM386 is loaded. Additionally, if I try to load "loadsbos.sys" driver in the config.sys
it says "No Ultrasound chip detected".

I also discovered that the default configuration of the GUS sets the port to 240 and the emulated Blaster to 220 in autoexec.bat environment, but in the after running the setup (without EMM386) it will set blaster to 240 (same as real Gravis).
Using port 240 for Sound Blaster will produce same (I tested both *original* SB emulation and GUS with SBOS) sound effects that the original Sound Blaster in Prince of Persia v1. 3, but the game locks up when prince opens the door to level 2.

MEGA-EM 2.07 works ok with Incredible Machine II but not in first version.

I found a 3.x version of MEGA-EM that merges SBOS the old Mega-EM and Ultramid, but it rquires EMS memory and lock up the emulation too.

I have some hypothesis,after using the GUS emulation.

1. There is a conflict In the use of umb memory regions, hence the problem with EMM386. I read that SBOS 3.82 try to load itself in UMB memory
2. Some functions of the GUS are not emulated
3. i don not know if the emulation of GUS was ported from dosbox, but found a bug in "PC globe maps and facts" from 1994 when using GUS emulation and drivers in Win 3.1 that were the same in previus releases of PCEM, ( it was related to national anthems musics not working).
4. Dosbox do not emulate NMI or V86 mode so SBOS and Mega-EM are not posible to use. EMS memory are emulated using "real mode" like in the old EMS memory boards in 8086/286 systems. So this problem never arised in Dosbox.

Again, it's nobody's fault. I know writing all the emulated hardware from scratch can be near impossible. I'm only interested in accuracy and I know too that PCEM is designed to be more accurate than dosbox which was focused on DOS games compatibility only.

Happy Holidays!