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vsbhda.txt
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vsbhda.txt
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1. About
VSBHDA is a SoundBlaster emulation program for DOS. It's a fork of SBEMU,
compatible with the standard HDPMI DPMI hosts included in the HX runtime
package.
2. Requirements
Besides VSBHDA the following external binaries are needed:
- HDPMI32i : included in the HX DOS extender runtime package HXRT.
Download from https://github.com/Baron-von-Riedesel/HX.
Version of HDPMI32i must be v3.21 or better.
- HDPMI16i : also included in the HX DOS extender runtime package HXRT.
This is the 16-bit variant of the DPMI host.
- Jemm : To be found at https://github.com/Baron-von-Riedesel/Jemm.
This package will also contain JLOAD.EXE and QPIEMU.DLL.
Version must be at least v5.84. Jemm - or rather QPIEMU.DLL
- is necessary for VSBHDA's support for "real-mode" games.
Alternately, Qemm may be used.
3. Usage
VSBHDA consists of two programs: vsbhda.exe and vsbhda16.exe. Due to the
nature of DPMI, 16-bit and 32-bit DPMI clients must at least have separate
interrupt tables. This implies that - at least for DPMI v0.9 - there's no
good way for a 32-bit client to provide services for a 16-bit client - and
vice versa. Hence vsbhda.exe can only support 32-bit protected-mode games,
while vsbhda16 is limited to 16-bit protected-mode ones. Both variants
support real-mode games, though.
The steps to load the VSBHDA emulation layer are
- load JemmEx/Jemm386 in CONFIG.SYS
- set environment variable BLASTER
- run "JLoad QPIEMU.DLL"
- optionally run "JLoad JHDPMI.DLL" (see below)
The rest depends on the game that is to run:
32-bit 16-bit
--------------------------------------
HDPMI32i -x HDPMI16i -x
VSBHDA VSBHDA16
Files start.bat and start16.bat are examples how this startup sequence
might look like. UNINST.COM may be used to unload the programs. This must
be done if one wants to switch from 32-bit to 16-bit and vice versa; the
programs themselves have problems to detect the presence of the other
variant.
As already mentioned, QPIEMU.DLL is needed for real-mode port trapping;
also, if it's not installed, UNINST.COM won't work.
Vsbhda16.exe loads file sndcard.drv during initialization. Due to
limitations of the 16-bit environment ( a module's code/data segments must
not exceed 64 kB ) the binary had to be split into two parts.
With the BLASTER variable one can select what card VSBHDA is to emulate:
SB, SB Pro or SB 16; for example: "SET BLASTER=A220 I7 D1 H5 T6" will select
a SB16.
VSBHDA will understand a few commandline options. Some, like /A, /I, /D, /H,
/P or /T, are similar to the settings of the BLASTER environment variable
( this variable is NOT altered by VSBHDA ). The others are:
/OPL : Set OPL3 emulation
/PM : Set protected-mode support
/RM : Set real-mode support
/F : Set frequency
/VOL : Set master volume
/BS : Set PCM buffer size
/SD : Set slowdown factor
/O : Set output widget (HDA only)
/DEV : Set start index for device scan (HDA only)
- /F: note that if the frequency isn't supported by the codec, it can't be
used - that's also true for the default value ( 22050 Hz ). In such cases
VSBHDA will use a frequency that is supported AND is at least the value
set by /F ( or the default ).
- /VOL: needs a one-digit value ( /VOL0 - /VOL9 ). This option sets the
volume of the real sound hardware ( hda, ac97 ).
- /BS: the PCM buffer is used for temporary storage of PCM samples, needed
for format conversions. The argument is the number of 4kB pages used as
buffer; the default value of 16 (means 64 kB) should be ok for virtual
all cases, setting it too small will result in page faults.
- /SD: purpose is to slowdown games. Needs a numeric argument, for example
/SD100. If this argument is too high, the machine won't respond anymore.
This option uses the RDTSC instruction - Although usually no problem, this
instruction is priviledged if bit TSD (bit 2) is set in register CR4; then
running this instruction in ring3 will cause a GPF.
4. Details/Hints
4.1 JHDPMI.DLL
This JLM is recommended to be loaded before the vsbhda binary. It doesn't
supply any features for vsbhda directly, but enhances DPMI compliance of
hdpmi. It ensures that the DPMI host will be the first to receive interrupt
requests that occur in v86-mode, without the need to modify IVT vectors.
The utility JHDSTAT.EXE makes JHDPMI display its status. One may see what
IVT vectors are hooked and how often the hook address has been called.
4.2 SETPVI/RESPVI
A few protected-mode games may "freeze" with the default settings of VSBHDA;
or, it the game uses the Rational DOS extender (DOS4/GW), a register dump may
be displayed, with the error message "Transfer buffer overflow". Then there's
a chance that running SETPVI may fix that. Note that SETPVI won't work with
Qemm.
SETPVI will set the PVI flag in cpu register CR4, RESPVI will reset it. When
this bit is set, any protected-mode program running in ring 3 is unable to
change the interrupt flag (IF), since CLI/STI will modify the virtual
interrupt flag (VIF) only.
4.3 Extended Memory
Some DOS games refuse to run if too much extended memory is available. There
are some simple software workarounds for such issues:
- HDPMI's -x cmdline option: this restricts the free DPMI memory to 256MB.
Optionally, this can be further reduced by appending a digit to -x: -x2
reduces free memory to 64MB, -x4 to 16MB. However, this is a soft limit,
since it's just the amount of memory that's reported as free - the program
may still allocate more than that, if available.
- XMSRes: tool to reduce free XMS memory. This TSR can be uninstalled, so
the reduction may be reverted without reboot.
- JemmEx's MAXEXT option: tells JemmEx's XMS host to supply a max. amount of
extended memory.
4.4 Jemm's NOVCPI Option
If VSBHDA is to work for DOS protected-mode games, those games must use the
HDPMI32i/HDPMI16i DPMI host. This is usually no problem, because there's an
API to detect the presence of such a host. However, games may ignore an
installed DPMI host and use the so-called VCPI API instead to run their very
own low-level code. This will actually deactivate VSBHDA for the game. To
cover such cases, Jemm386/JemmEx offers the NOVCPI option. This option must
be set *after* VSBHDA has been loaded and *before* the game is launched.
5. Error Messages
- "Sound card IRQ conflict": the sound hardware uses the very same IRQ number
than the emulated SB ( 2, 5 or 7 ). This is currently rejected ( it may
confuse the emulator ).
- "SB found - probably VSBHDA already installed": a SoundBlaster was
detected. If it's due to an installed VSBHDA, use UNINST.COM to remove the
running VSBHDA from memory.
- "Jemm/Qemm not installed, or version below 7.03: x.x - disable real-mode
support": the so-called QPI wasn't found. It's either supplied by Qemm or
Jemm ( with QPIEMU.DLL loaded ).
- "HDPMI not installed - disable protected-mode support": running VSBHDA
under another DPMI host is possible, but not recommended.
- "Error: Failed installing IO port trap for real-mode.": the v86-monitor
(Qemm/Jemm) returned something unexpected when the port trapping API was
called.
- "Error: Failed installing IO port trap for protected-mode.": the DPMI
hosts HDPMI32i/HDPMI16i are the only ones implementing the protected-mode
port trapping API used by VSBHDA.
- "Pin <n> (<type>) used for output": HDA only; this is a warning that the
expected output device type ( lineout|speaker|headphone ) wasn't found
and hence another one had to be used.
6. Compatibility Issues
Here are some games listed that require special actions:
- Blood: setting SB IRQ to 2 or 5 may be required. Generally, on some
machines the DOS/4GW DOS extender has problems with IRQ 7.
- Jungle Book: needs SETPVI.EXE to be run before launched.