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Patching VxD for ES1869 drivers to enable Windows 9x dos box midi support

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First post, by eshaz

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Hey all,

I recently purchased a Compaq Armada 1500c laptop which sports the ES1869 sound chip. I modded it a bit to reduce the headphone out volume and added a few extra filtering capacitors to reduce noise, and it sounds great! However, I am unable to get OPL2 / OPL3 sound to work in the Windows 98 dosbox when using the ES1869 drivers (latest VxD version). I've done the requisite ESSCFG, enabling / disabling PnP, ensuring the resources are configured properly, trying different driver versions, etc. I do have a work around, which is to use the ES1868 drivers (latest VxD version), however this disables the 3D spatializer and ability to playback 48kHz sound.

I should note that this issue has been discussed a few times on this forum, with no apparent solution. Some folks claimed to have fixed it, but myself and others are unable to reproduce the fix. If someone could share a solution that is reproducible, that would be extremely appreciated:

Similar Unresolved Topics

help getting soundcard (ES1869) working windows 98SE: help getting soundcard (ES1869) working windows 98SE
Issues getting ESS 1869 running in Win98 DOS mode: Issues getting ESS 1869 running in Win98 DOS mode

I'm thinking this is a software issue, since the ES1868 drivers enable Win9x dos box midi support just fine. I'm a software engineer by trade and would like to figure out how or if it's possible to patch the actual ES1869 drivers to resolve this issue. I tried disassembling the drivers using Sourcer and IDA, but I really don't know where to start. I'm thinking maybe compare the ES1868 and ES1869 dissassembled code side by side and look for differences, or search for the register values that control OPL3 support...

Does anyone here have experience patching or building VxD / sound card drivers?

Maybe a separate utility could be created to properly enable OPL3 that could be run before opening the Win9x dosbox?

Maybe there's the really rare chance someone has the original source code for this driver sitting around? 😀

Reply 1 of 3, by eshaz

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It turns out that ESS Technology (https://www.esstech.com ) is still around and still making audio chips. I'm considering contacting them and asking if they are willing to open source or at least allow me to access the source code for the ES1869 windows driver with the intention of fixing this OPL3 compatibility bug and releasing a new driver build with the fix. Hopefully they still have the source code.

Does anyone here have any suggestions or pointers on how to effectively send this request? I don't want it to just end up in the junk box. 😀

I know some of you here have developed new hardware to emulate old cards and have other DOS / Windows 9x dev experience. Would any of you be interested in pairing up with me on this effort? It would be nice to have this effort be community driven, if there is interest.

Reply 2 of 3, by bakemono

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I don't know much about VxDs or win9x but I don't think it disables I/O permissions for DOS programs (?) which would suggest that the ESS driver has disabled the OPL3 by way of a configuration feature in the ESS chip itself. The ESS1869 datasheet is online somewhere, and on pg. 41 it shows a power management register which contains a bit to disable the FM interface. It could be something that simple. Maybe you could just open a DOS window and then run a small QBASIC/DEBUG/Asm program to change the register value and re-enable FM. Although it's possible the driver would mess with it again after a period of time. If you need to hack the driver, looking for OUT instructions (or the equivalent API call, if there is such a thing for VxDs) and comparing them with the datasheet would be a good place to start.

again another retro game on itch: https://90soft90.itch.io/shmup-salad

Reply 3 of 3, by eshaz

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Thanks for the input! That makes sense to use the Windows dos box to read / write to the IO ports to reconfigure the chip. I started looking into this with DEBUG, but the power register (Audio_Base+7h i.e. 0x227) had the same value 0x0A with both drivers. I'll keep experimenting.

I should note that the OPL3 still doesn't work after booting to Windows with the ES1869 drivers and then exiting Windows into DOS mode.

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