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Cmedia CMI8738 - maybe its Biggest Secret

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Reply 20 of 60, by ShovelKnight

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kodi wrote:

that's the eternal question, you need to check your South Bridge - if it's VT823x or newer, then you're out of luck.

If I recall correctly, VT8231 supports DDMA but later south bridges (VT8235 etc.) do not.

Reply 22 of 60, by kodi

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yawetaG wrote:

I have here a Asus CUSI-M motherboard with a CMI 8738/PCI-SX HRTF Audio Com M2M08-037D 0111UGGD. Driver CD includes DOS drivers.

"037D" - that's same revision as mine. so, that one doesn't allow me to write to the DDMA register.

anyone with revision "033" or with CMI8338? those are before "037" and maybe what's inside that old datasheet is valid only for one of them (or for both).

Reply 23 of 60, by kodi

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ShovelKnight wrote:
kodi wrote:

that's the eternal question, you need to check your South Bridge - if it's VT823x or newer, then you're out of luck.

If I recall correctly, VT8231 supports DDMA but later south bridges (VT8235 etc.) do not.

nope and i don't see a point we even argue on this, when VIA Datasheet are publicly available, the fact are:

* VT8231 Preliminary datasheet - it has note in it:

Initial release based on 82C686A “Super South” Data Sheet revision 1.42

and that datasheet wrongly states DDMA for VT8231, but it's just copy and paste leftover from 82C686A datasheet.

* VT8231 Final datasheet - no any mention of DDMA support, in fact the addresses for DDMA settings are used for entirely different settings, i.e. they are documented that are no longer for DDMA.

So, VT8231 is the exact point where VIA removed DDMA support. Also, I have motherboard with VT8231 and DDMA is not there - double check that the VT8231 final datasheet release is correct.

Reply 24 of 60, by kodi

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dionb wrote:

VT823x on an ApolloPro133A? Nope, this is a DFI TA-64, pairing the 694X with an old 596B.

that one i believe doesn't support DDMA, but I am not sure, because 596 was intended as laptop chipset. So, I believe it has only PC-PCI/SBLink support (as that was used for a docking station with ISA slots inside). That's why usually desktop motherboards with 596 are the only VIA motherboards that have SBLink header. If anyone have seen VIA-based motherboard with SBLink and South Bridge different than 596 - let me know. I myself have a lot questions about 596 compared to VT82C586.

Reply 25 of 60, by Stretch

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I have a CMI8738 model 33 and also a model 55. Unfortunately, my Pentium 2 computer won't POST and I already swapped video card and PSU, so I won't be able to test until I swap out the motherboard. I do have a 440 BX motherboard which I will try to install this weekend.

Win10 - AMD Ryzen 9 3900 - 16 GB - GeForce RTX 2060S - Sound BlasterX AE5-Plus
Win98SE - ASRock 775i65G R3.0 - Celeron 2.2 GHz - 2 GB - GeForce FX5700 - Audigy 2 ZS
Win98SE - Via Apollo Pro Mobo - Pentium II 233 - 256 MB - Voodoo 3 1000 - Yamaha YMF724

Reply 26 of 60, by kodi

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Stretch wrote:

I have a CMI8738 model 33

great, i will prepare and post here small tool you can run to check if on rev 33, address 40h is writable.

[EDIT] I've just found my card based on Trident 4DWave-DX chipset - it uses same 40h for DDMA. So, that will allow me to do good research from my side. that's good, some small progress, but at the end, we should be able to get to the bottom of what is valid for which Cmedia revision. currently, my rev 37D is no go for DDMA and so rev 33 is the prime candidate for the information in the datasheet.

Reply 27 of 60, by yawetaG

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kodi wrote:
yawetaG wrote:

I have here a Asus CUSI-M motherboard with a CMI 8738/PCI-SX HRTF Audio Com M2M08-037D 0111UGGD. Driver CD includes DOS drivers.

"037D" - that's same revision as mine. so, that one doesn't allow me to write to the DDMA register.

Yeah, but the string before the "037D" is different, which may indicate a different model, so we won't know for sure until I try.

What is curious is that the motherboard manual states it has FM and wavetable synthesis, yet a Yamaha softsynth is included on the driver CD...

Reply 28 of 60, by kodi

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yawetaG wrote:

Yeah, but the string before the "037D" is different, which may indicate a different model, so we won't know for sure until I try.

that i believe is just a batch number from the factory.

yawetaG wrote:

What is curious is that the motherboard manual states it has FM and wavetable synthesis, yet a Yamaha softsynth is included on the driver CD...

nothing about Hardware wavetable in the CMedia daatsheets, but FM is there for sure and on 37D it can output via digital out - that's why there is thread in this forum for pass-trough of FM on modern systems using CMI8738.

anyway, no matter if we find revision of CMI8738 that has DDMA or not, my effort on this will still lead to release of some tools - for example tools to enable DDMA on compatible Intel, VIA chipsets, etc. Looking now at this - the biggest problem of back then was that they did not include that as option in the BIOS - where I think that belongs. it's a shame, because properly done DDMA has to be like close to 100% compatible and indistinguishable from ISA sound card. it also needs no driver - just small initialization to tell the sound card and the chipset to use DDMA.

Reply 29 of 60, by dionb

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kodi wrote:
dionb wrote:

VT823x on an ApolloPro133A? Nope, this is a DFI TA-64, pairing the 694X with an old 596B.

that one i believe doesn't support DDMA, but I am not sure, because 596 was intended as laptop chipset. So, I believe it has only PC-PCI/SBLink support (as that was used for a docking station with ISA slots inside). That's why usually desktop motherboards with 596 are the only VIA motherboards that have SBLink header. If anyone have seen VIA-based motherboard with SBLink and South Bridge different than 596 - let me know. I myself have a lot questions about 596 compared to VT82C586.

Right, scratch that. Fortunately I have another system with an MSI MS-6168rev2, with i440BX and PIIX4E southbridge that I needed to move to my workshop anyway. That one should do DDMA. What can I test?

Out of interest - what is the added value of DDMA if the only chipsets supporting it are ones supporting regular ISA anyway?

Reply 30 of 60, by The Serpent Rider

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what is the added value of DDMA if the only chipsets supporting it are ones supporting regular ISA anyway?

For example, ASUS and Gigabyte* dropped ISA slots on KT133A boards completely. And there's usually only one slot anyway.

*Gigabyte board has solder points for one ISA slot, but apparently it's not functional (thread on Vogons).

Get up, come on get down with the sickness
Open up your hate, and let it flow into me

Reply 31 of 60, by bmwsvsu

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I have an old Bki810 bookshelf PC (Socket 370 Celeron) with no expansion ports but it does have a CMI sound chip:

SoundPro
HT8738AM / PCI
M7H31-033C

So I'll be curious to see if you ever get this figured out.

Reply 32 of 60, by kodi

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dionb wrote:

Out of interest - what is the added value of DDMA if the only chipsets supporting it are ones supporting regular ISA anyway?

that's not true, for example VT82C686 has close to excellent DDMA support and there are many motherboards with that chipset without any ISA slots. also, some PCI cards have interesting features - for example cmi8738 ability to output OPL3 via its digital outputs. all pci cards also have much better sound-to-noise ratio, i.e. are less noisy. last, but not least, because it's probably most important point - SiS chipsets have excellent, really excellent, on par with the benchmark 440bx, DDMA support and they supported that up to SiS963 Sound Bridge. So, there are really countless AthlonXP and Pentium 4 motherboards with SiS chipset that have DDMA.

I started working on this, on this project, exactly to get DDMA on my P4 SiS motherboard (no any vendor tool works on SiS) and today I have huge progress and get it running with 4DWave-NX based card - no any third party tools or tools from the vendors, just my small tool. So, today was a lot of run - running Impulse Tracker on 3+ GHz P4 system plus the sound is really clear, because just analog part of PCI card like 4DWave-NX is much better.

P.S. VIA is hell though. VT82C686 as I mentioned close to excellent, but on VT82C586 I cannot get DDMA working and now I think their datasheet is wrong in fact it's similar problem as what I have with CMI8738 037D - I cannot write to the address in VT82C586 that is supposed to control DDMA. One more time Intel and SiS are equally good for DDMA on my tests, but with Intel you have DDMA only with ancient 430TX and 440BX, while with SiS you have it up to modern times. I mean motherboards with SiS963/SiS962, etc are quite modern compared to 430TX/440BX. However, no vendor tool supports those new SiS chipsets and so tools like the one I made today for 4DWave-NX are needed.

Reply 33 of 60, by gdjacobs

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For some reason, Kamerat was able to initialize and use some cards on a vt8233 south bridge with DDMA mode. VIA may not test it, they don't advertise it, but they may not have deleted DDMA functionality from the ASIC, at least in the early V-Link south bridges.
PCI sound cards and Chipsets from various manufacturers...

All hail the Great Capacitor Brand Finder

Reply 35 of 60, by kodi

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gdjacobs wrote:

For some reason, Kamerat was able to initialize and use some cards on a vt8233 south bridge with DDMA mode.

i am 99.9% sure Kamerat is mistaken, because for FM801 mentioned I don't know (if I can find any datasheets I will check more), but the other one ALS4000 - has emulation mode that works even on later VIA South Bridges like VT8237/9 (tested by me), but that's not DDMA. So, Kamerat is welcomed to jump in and give more details.

As from my side really this transformed in making myself (and respectively the community) Swiss-army-knife set of tools for DDMA, I think maybe one set of tools I can make is tools that check from sound card side its settings what mode they are really running/using. that way tell the user for sure is it DDMA or something else.

It's big mess from my side, but in 1-2 weeks, probably i will start releasing Proof-of-Concept tools here. Maybe, made separate thread as "master" thread for DDMA information, because already there are huge gabs between datasheets information, what is spreading as information among the community, etc. and what is really true especially based on empirical evidence.

gdjacobs wrote:

VIA may not test it, they don't advertise it, but they may not have deleted DDMA functionality from the ASIC

the problem is that if they "haven't deleted it" from the ASIC, they moved it to some secret/undocumented addresses, which is doubtful, because DDMA addresses even on the very fist VT8231 (after VT82C686) are used for another functionalities and those functionalities are confirmed by open-source chipset drivers like those for Linux, not just the datasheets, i.e. confirmed empirically. I hope that clarifies my point. I really don't see a reason why if they kept it, to changes the control addresses and even reuse the old control addresses for other things.

Auzner wrote:

Embedded on a S7 SBC with a SiS5598.

i like the chipset, i don't have motherboard with such chipset. do you have other PCI sound cards? if you're willing i want to use you to test DDMA tool for SiS5598, but you need PCI audio card that can do DDMA for sure, i.e. first we make Sis5598 working.

Last edited by kodi on 2019-11-17, 15:35. Edited 2 times in total.

Reply 37 of 60, by The Serpent Rider

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T82C686 as I mentioned close to excellent, but on VT82C586 I cannot get DDMA working

Technically it's not required for VT82C586 anyway, because they usually have 2-3 ISA slots.

Get up, come on get down with the sickness
Open up your hate, and let it flow into me

Reply 38 of 60, by Stretch

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I couldn't get my Pentium 2 computer working. So, I installed a CMI 8738 model 55 in my Pentium 4 ASRock 775i65G motherboard (Intel ICH5 southbridge).

I heard adlib music and sound blaster sfx in Wolfenstein-3d in MS-DOS, so that means DDMA is working with the official driver.

I used the MS-DOS driver supplied with the Turtle Beach Riviera rivi_dos.zip, which I believe it the latest driver available.

Win10 - AMD Ryzen 9 3900 - 16 GB - GeForce RTX 2060S - Sound BlasterX AE5-Plus
Win98SE - ASRock 775i65G R3.0 - Celeron 2.2 GHz - 2 GB - GeForce FX5700 - Audigy 2 ZS
Win98SE - Via Apollo Pro Mobo - Pentium II 233 - 256 MB - Voodoo 3 1000 - Yamaha YMF724

Reply 39 of 60, by kodi

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The Serpent Rider wrote:

T82C686 as I mentioned close to excellent, but on VT82C586 I cannot get DDMA working

Technically it's not required for VT82C586 anyway, because they usually have 2-3 ISA slots.

both agree and disagree, because my main point is that VIA states DDMA support in their datasheet, which I cannot confirm empirically.

kodi wrote:

Maybe, made separate thread as "master" thread for DDMA information, because already there are huge gabs between datasheets information....

ok, here it is:
DDMA and PCPCI for Low IQ Individuals (Me included)

will add more when have spare time and mood about it.

Stretch wrote:

I heard adlib music and sound blaster sfx in Wolfenstein-3d in MS-DOS, so that means DDMA is working with the official driver.

no, it means some form of (software) emulation is working... DDMA is when both the mainboard chipset and the sound-card chipset are set to use it. anyway, keep an eye on the above thread, where i will try to make it clear for everyone to best of my ability.