Resources on an XT are always fun. You only have a few IRQs and DMAs to play with.

You can choose between IRQ 2, 3 5 or 7.

Their normal allocation:
2: EGA/VGA (not always used)
3: COM2
5: HDD controller
7: Parallel port

Depending on what you use, I'd suggest using IRQ 3 or 7. IRQ2 might work, depending on your video card, but is not always selectable in games, so I'd only try that if absolutely can't get IRQ 3 or 7 working.

That means you need to disable either second serial port or parallel port. You say an XT "has no Bios". That's incorrect, every PC compatible has a BIOS. An XT just doesn't have an interactive setup program for it. Moreover, ports are configured in hardware with jumpers. You'd need to disable COM2 or LPT1 on the I/O controller, which I believe is integrated into the motherboard on this model.

Same for the card: no software involved, you just configure with jumpers. A220h I7 is the default for sound cards on XT, so nothing strange there. A220h should never really be a problem - and the fact fmradio.exe plays shows that you're able to access the OPL2 for FM synth, you just need to find a free IRQ for SB DA.

Now, challenge is that I'm unable to find jumper manuals for that Commodore system, but somewhere there needs to be a set of jumpers for I/O. Failing that, try IRQ2 after all.

Use IO 220h, IRQ 7, DMA 1.

No need to disable the LPT:
- if there's nothing connected, it won't generate interrupts
- if there's a printer, it's operated in polling mode - again, no interrupts

And remember to add this to AUTOEXEC.BAT:

set BLASTER=A220 I7 D1

Edit: Aztech's FTP site is no longer available... has anybody made a mirror, or is it time for mourning ceremony?

http://vogonsdrivers.com/getfile.php?fileid=788&menustate=0

Been on Vogonsdrivers for a long time fortunately, although not really needed in this case.

Grzyb wrote on 2023-05-16, 10:17:

Use IO 220h, IRQ 7, DMA 1. […]
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Use IO 220h, IRQ 7, DMA 1.

No need to disable the LPT:
- if there's nothing connected, it won't generate interrupts
- if there's a printer, it's operated in polling mode - again, no interrupts

That's wrong!

No no, it's not. Just kidding! ^^

Um, as far as I know, the IRQ for LPTx is rarely used in pratice.
- OS/2 is one of the systems which uses it (for printing, I think), Windows 9x maybe if told so.
- DOS programs and 16-Bit Windows or GEM or PC GEOS rather don't use it, AFAIK.

What can be done, also: Discreet LPT chips installed on ISA card (serial/parallel; Hercules; multi-i/o) can be hacked.
By cutting the IRQ line going its way from its pin on ISA edge connector to the parallel chip or the glue logic/buffers.
In its simplest form, this "hack" involves not setting an IRQ jumper for LPTx on ISA card.

Grzyb wrote on 2023-05-16, 10:17:

Use IO 220h, IRQ 7, DMA 1.

Exactly.
This was the factory configuration of Sound Blasters until around the introduction of the SB16, when they moved to IRQ5 (LPT2).
It is not entirely clear why they changed it.
I had an early SB Pro 2, which has always run on IRQ7 without issue.
Later SB Pro 2 cards were configured as IRQ5.

Some early software, such as Stellar 7, has the IRQ hardcoded to 7, so they won't work correctly with a card at IRQ5.
Most software will either read the BLASTER statement, or allow you to set the IO parameters via a setup/install tool.

Scali wrote on 2023-05-16, 12:16:

It is not entirely clear why they changed it.

I would say it's pretty clear - Sound Blaster: From IRQ7 to IRQ5, when and why?

Grzyb wrote on 2023-05-16, 12:25:

Scali wrote on 2023-05-16, 12:16:

It is not entirely clear why they changed it.

I would say it's pretty clear - Sound Blaster: From IRQ7 to IRQ5, when and why?

The bit about ISA bus not being able to share IRQs is confusing, though.

My Media Vision Pro Audio Spectrum 16 cards do have ID jumpers, so multiple cards can be installed and used in a single PC.

Considering the shortage on resources, sharing is absolutely required here.
There are simply not enough resources to simultaneously use four cards in one PC in a different way.

BTW: Commodore PC 10-III and 20-III have the dedicated mouse port, AFAIK for the same mouse as Amiga.
Any idea which IRQ that port uses?

Thanks for all your answer. I will try again next weekend to make it work and post all here. Anyway it seems a trial-and-error-thing.😀

Good luck! 😀 🤞

Grzyb wrote on 2023-05-16, 12:41:

BTW: Commodore PC 10-III and 20-III have the dedicated mouse port, AFAIK for the same mouse as Amiga.
Any idea which IRQ that port uses?

I assume it's IRQ2, but I'm not sure. Commodore and Atari were weird. 🤷

They occasionally both ported stuff over from their home computer line to their PC line.
Which in both cases was like a separate computer division each, more or less.

They also made strange PC/AT computers based on PC/XT technology;
essentially XT looking PCs* with an 80286 slapped on (thinking of PC40-III). Very weird.

Btw, bus mice were generally strange. The original PC bus mouse and the MS InPort mouse are similar, but different.
Both use the same set of basic registers/basic BIOS calls, but the pinout and electronics were different.
The old interface card had a DE9 connector and a parallel port chip (always interrupting CPU); while the new InPort model had a PS/2 style plug.
Funnily, the InPort mouse itself could be put in serial mouse mode if an adapter to DE9 was used (MS Mouse compatible).

Then, there's ATI with the ATI VGA Wonder series.. They had a bus mouse interface in the SVGA chipset.
Or the Schneider Tower AT/Euro AT.. They had an on-board bus mouse, too. It was part of the Super EGA chip, I believe.
The Schneider/Amstrad PC1512 and 1640 had a weird keyboard-based mouse. The mouse used the keyboard controller.

(* DIL RAM, discreet ISA connectors/two pieces, full-size PCB, DIP switches, re-purposed XT chassis, keyboards with XT era layout)

Jo22 wrote on 2023-05-16, 12:37:

The bit about ISA bus not being able to share IRQs is confusing, though.

'Sharing' IRQs in the context of the ISA bus basically means that whenever you get an interrupt, the handler should check which device signaled the interrupt.
Most software doesn't do this in practice, and just assumes that the IRQ comes from the device they expect.
But a lot of hardware has some kind of status register where you can see if it has a pending interrupt.
So sharing IRQ basically means that the handler checks all possible devices that could generate the interrupt, to find the one that actually did.
Under controlled circumstances, you can indeed use multiple devices with a single IRQ that way.

Grzyb wrote on 2023-05-16, 12:41:

BTW: Commodore PC 10-III and 20-III have the dedicated mouse port, AFAIK for the same mouse as Amiga.
Any idea which IRQ that port uses?

Pretty sure it's IRQ2.

Grzyb wrote on 2023-05-16, 12:25:

I would say it's pretty clear - Sound Blaster: From IRQ7 to IRQ5, when and why?

I don't think the explanation of 'dropping XTs' makes sense in the case of the SB Pro 2.
That card has always supported XTs, so why would they switch from IRQ7 to IRQ5 during its lifetime?

^ maybe because the SBPRO was released after the XT era and IRQ5 was free in the majority of setups of the time while IRQ7 still remained the standard for LPT?
I think it was decided to avoid extra support time, there are some systems that even if nothing is connected to LPT they still don't like IRQ7 being used for other devices (the 386sx amstrad megapc/7386sx systems do this bs)

I don't think the SB Pro was ever marketed as an AT-only card. I have an early one, I'll have to see if I can find my manual and see if it says anything about minimum requirements.
And IRQ5 is an issue with many XT HDD controllers, while a HDD was pretty much a requirement for using the SB Pro.

Scali wrote on 2023-05-17, 10:19:

I don't think the SB Pro was ever marketed as an AT-only card.
And IRQ5 is an issue with many XT HDD controllers, while a HDD was pretty much a requirement for using the SB Pro.

SBRPO released in 1991 didn't exactly have the XT systems as it's target , this is what I am trying to say
the IRQ change makes sense if you consider that by then the target systems were 286/386 ones with standard IDE controllers
(maybe some 286 systems were still sold with MFM HDDs but these would be the exception IMHO)
at least that's my take on the 7->5 change so take it with a grain of salt , it's my guesstimate 😁
(just to be clear I am not claiming to be correct , just presenting why I think the change happened)

Yes, ATs have a second PIC, so they have more IRQ channels. Harddisk controllers generally use IRQ14 and IRQ15 on ATs, not IRQ5.
The SB Pro also supports using IRQ10, which is on the second PIC. That one won't work on an XT.

Scali wrote on 2023-05-17, 10:19:

I don't think the SB Pro was ever marketed as an AT-only card. I have an early one, I'll have to see if I can find my manual and see if it says anything about minimum requirements.

This manual - https://www.manualslib.com/manual/1802842/Cre … 20Blaster%20Pro - states that "IBM 286, 386, 486, or 100% compatibles" are required.

Also, I'm wondering about LPT devices other than printers, like external disk drives and LAN adapters...
they may actually use the LPT IRQ, so one more reason to avoid using IRQ 7 for sound as soon as XTs disappeared from the market.

Note that even the earliest Sound Blaster CT1320 has an option to use IRQ 5, so it was reasonable to expect all existing software with SB support to support the SB on IRQ 5.
And those few exceptions hardcoded for IRQ 7 were easily dismissed as buggy.

Grzyb wrote on 2023-05-17, 12:39:

This manual - https://www.manualslib.com/manual/1802842/Cre … 20Blaster%20Pro - states that "IBM 286, 386, 486, or 100% compatibles" are required.

Yea, but that's the new-style manual (same as SB16), apparently from 1994, so that is probably bundled with a card that was configured as IRQ5 anyway.
I wonder if it has always been like that. As I say, I have an old card, that was IRQ7, and the old-style manual and box.

Grzyb wrote on 2023-05-17, 12:39:

Note that even the earliest Sound Blaster CT1320 has an option to use IRQ 5, so it was reasonable to expect all existing software with SB support to support the SB on IRQ 5.
And those few exceptions hardcoded for IRQ 7 were easily dismissed as buggy.

They also supported IRQ2 and IRQ3.
IRQ2 can't be used on ATs because of the cascading setup of the second PIC (although SB Pro still offers the option)
IRQ3 was dropped on the SB Pro, and instead IRQ10 was offered.
Pretty sure that IRQ10 is going to be troublesome with a lot of software written for the original SB, that didn't have the option of IRQ10 (or using the second PIC in general).

Of course hardcoded software is buggy, but that doesn't make the problem go away.
The A220 I7 D1 configuration is the original stock configuration, and is supported by most software.
Aside from hardcoded IRQ, some software may also hardcode the base address and/or DMA channel.