Hi,

how much RAM does Impulse Tracker need? I would try reducing the RAM to 4MB, disable Cache in the BIOS and see if it starts. Are you using an interposer for the Am486DX4-100? Because the Soyo SY-025D2 is a rather old 486 board without an VRM, so it will do only 5 volts and not the needed 3.3 volts. That is, unless I've looked up something wrong 😁

Impulse Tracker uses EMS, a thing to keep in mind. Also you can try to start Impulse Tracker with /S7 which selects the Gravis UltraSound driver. If a GUS and a Sound Blaster are available it will choose the Sound Blaster by default in my experience.

Stesch wrote on 2025-07-21, 08:44:

Are you using an interposer for the Am486DX4-100? Because the Soyo SY-025D2 is a rather old 486 board without an VRM, so it will do only 5 volts and not the needed 3.3 volts.

Of course! I've already received it with the voltage adapter.

Rawit wrote on 2025-07-21, 09:48:

Impulse Tracker uses EMS, a thing to keep in mind. Also you can try to start Impulse Tracker with /S7 which selects the Gravis UltraSound driver. If a GUS and a Sound Blaster are available it will choose the Sound Blaster by default in my experience.

Yes, by default, IT selects SB16, so I need to use the S7 argument. However, it hangs when GUS, SB16, or PC speaker is selected.

But there are some interesting things...
1. If I install DX-33, then there are no problems with initialization
2. If I open the turbo contacts (enable slow mode) when using DX4-100, there is also no hanging. Then I can disable slow mode, and IT will work normally.

So looks like this problem is speed-related. But it's strange, because IT successfully works with PIII-500, but why are there problems with "high-speed" DX4...

Normal/Slow modes:

Bs0Dd wrote on 2025-07-23, 01:29:

Of course! I've already received it with the voltage adapter. […]
Show full quote

Stesch wrote on 2025-07-21, 08:44:

Are you using an interposer for the Am486DX4-100? Because the Soyo SY-025D2 is a rather old 486 board without an VRM, so it will do only 5 volts and not the needed 3.3 volts.

Of course! I've already received it with the voltage adapter.

Photo

Rawit wrote on 2025-07-21, 09:48:

Impulse Tracker uses EMS, a thing to keep in mind. Also you can try to start Impulse Tracker with /S7 which selects the Gravis UltraSound driver. If a GUS and a Sound Blaster are available it will choose the Sound Blaster by default in my experience.

Yes, by default, IT selects SB16, so I need to use the S7 argument. However, it hangs when GUS, SB16, or PC speaker is selected.

But there are some interesting things...
1. If I install DX-33, then there are no problems with initialization
2. If I open the turbo contacts (enable slow mode) when using DX4-100, there is also no hanging. Then I can disable slow mode, and IT will work normally.

So looks like this problem is speed-related. But it's strange, because IT successfully works with PIII-500, but why are there problems with "high-speed" DX4...

Normal/Slow modes:

Photos

Now thats interesting. Does your interposer have a jumper for x2 multiplier? Perhaps you could try running the DX4 at 2x33Mhz and see if that works. My first 486 mainboard had the same SIS 85C461 chipset, but I've never installed something faster than a DX2 in there...

Bs0Dd wrote on 2025-07-23, 01:29:

So looks like this problem is speed-related. But it's strange, because IT successfully works with PIII-500, but why are there problems with "high-speed" DX4...

The difference is this is VLB mobo with the ISA bus tied as directly to CPU as it is possible for 486. Possibly overclocked? Did you check the clock divider setting in BIOS?
With anything PCI the ISA bus is a slave to PCI, and usually clocked at 8MHz with no options to change it. The latency is worse too due to all transactions going to PCI hub first, so any I/O will be slowed down and well within ISA specs.

So check your ISA clock or try running that DX4 at slower clock (25MHz) to see if that changes anything. Also keep in mind that DMA can't address above 16M and not all apps and games allocate the buffer in low memory. A simple way to overcome that is to allocate a SMARTDRV cache of 4-6 MiB to limit the amount of free memory. IIRC there are some HIMEM replacements that can be instructed to allocate from the top of memory, not sure now how original HIMEM does it.

Stesch wrote on 2025-07-23, 07:03:

Does your interposer have a jumper for x2 multiplier? Perhaps you could try running the DX4 at 2x33Mhz and see if that works.

No, it's just a voltage adapter. DX4 works with an x3 multiplier, so I can only 3x33 (~100) or 3x25 (75) MHz.

Deunan wrote on 2025-07-23, 10:22:

Possibly overclocked? Did you check the clock divider setting in BIOS?
So check your ISA clock or try running that DX4 at slower clock (25MHz) to see if that changes anything.

The ISA clock is set to 7.15 by default in the BIOS. Well, maybe this board is just too old for DX4, because the fastest processor it knows is a DX2-66.

Hmm, I was wrong. It seems that the computer does not actually freeze - only the keyboard stops working!
I recently received a COM mouse and connected it to the PC. When starting IT without slowing down, I can use the mouse without any problems, but the keyboard stops working completely.
This is even more strange behavior...

Bs0Dd wrote on 2025-07-30, 19:51:

Hmm, I was wrong. It seems that the computer does not actually freeze - only the keyboard stops working!
I recently received a COM mouse and connected it to the PC. When starting IT without slowing down, I can use the mouse without any problems, but the keyboard stops working completely.
This is even more strange behavior...

Perhaps it might be worth a try to mess around with the keyboard settings in BIOS then? For example, try to disable typematic rate setting if that's not already the case. How does it behave with programs other than Impulse Tracker? Do they show the same behavior?