aVd wrote on 2026-07-12, 07:11:

With my basic assembly skills I found, that in CMI8738 driver version 1.98 the value for register 0x21 is not 5, but 4. This is […]
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With my basic assembly skills I found, that in CMI8738 driver version 1.98 the value for register 0x21 is not 5, but 4. This is what my disassembler shows as code (comment on first three lines are added by me):

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1mov	dh,cs:data_20	; data_20 seems like BASE ADDRESS var.
2mov	dl,21h			; seems like BASE ADDRESS + 21h
3mov	al,4			; IS THIS WRONG VALUE???
4out	dx,al			; port 21h, 8259-1 int comands

I checked again the register settings in driver version 1.98 and this code is actually a dead one. Possibly result of previous version patching or very bad code writing regarding the quality of DOS driver and mixer:

1...
2mov	dh,cs:data_20
3mov	dl,21h
4mov	al,5	; 0x05 is set for 0x21 register
5out	dx,al	; 0x05 is written in 0x21 register
6jmp	short $+2
7jmp	short loc_23
8nop					; |
9mov	dh,cs:data_20	; |
10mov	dl,21h			; |--> this the dead code and no 0x04 is set for 0x21 register,
11mov	al,4			; |    it was already set to 0x05 above
12out	dx,al			; |
13jmp	short loc_23	; |
14loc_23:
15mov	dh,cs:data_20
16...

Register settings values in the driver seems Ok to me from what I managed to compare to the information from the official documentation. The only concern remains the IRQ, DMA, etc. settings code routines, which I'm not able to check or patch.

I admire you for not giving up yet, but I'm afraid we're going to hit a wall here, just as Stainlesscat predicted.

Hi, @Ydee,
I'm still not giving up, but "the wall hit me", due to my very basic x86 assembly knowledge and the lack of more detailed official documentation. To me "asking" an a.i. bots is not an option, so I'll start to learn how to read the assembly code better or I will ask someone way better than me for help.