UDMA is used in Win98SE (you can run SPEEDSYS HD from a Windows DOS box and get away with it and check the speed even though it admonishes you not to run it under Windows) while in DOS, the BIOS disk support generally falls back to PIO. Even then, it should not be this slow, although lack of Multiple Sectors Per Interrupt on most SSDs (assuming this SATA disk is one) hurts performance. There's no technical reason the BIOS couldn't use UDMA for Int 13h accesses, but PIO avoids having to implement VDS or triggering UDMA-related incompatibilities with picky drives.

Mike_ wrote on 2026-07-13, 17:09:

I have a system built on a KT133A based Gigabyte GA-7ZXE motherboard and an Athlon XP. I'm using a SATA disk through an Aliexpress SATA/IDE adapter and it's working fine in Windows 98 SE. However, read speed is very low in DOS.

Of course this isn't a huge problem as you can run most DOS games that benefit from the extra bandwidth from Windows, but still, I wonder what's causing this.

The attachment SSTIMG01.gif is no longer available

Actually the Athlon era VIA chipsets in PIO mode are that slow even without an adapter. You can try to load the VIA Bus Master(Ultra DMA) IDE driver from CONFIG.SYS to get better performance under DOS:

1DEVICE=C:\DOS\VIAIDE.SYS

jakethompson1 wrote on 2026-07-13, 17:19:

UDMA is used in Win98SE (you can run SPEEDSYS HD from a Windows DOS box and get away with it and check the speed even though it admonishes you not to run it under Windows) while in DOS, the BIOS disk support generally falls back to PIO. Even then, it should not be this slow, although lack of Multiple Sectors Per Interrupt on most SSDs (assuming this SATA disk is one) hurts performance. There's no technical reason the BIOS couldn't use UDMA for Int 13h accesses, but PIO avoids having to implement VDS or triggering UDMA-related incompatibilities with picky drives.

I tested it with HDTach and it does seem to work at about the speed you would expect from the IDE controller in Windows.

Falcosoft wrote on 2026-07-13, 18:27:

Actually the Athlon era VIA chipsets in PIO mode are that slow even without an adapter. You can try to load the VIA Bus Master(U […]
Show full quote

Actually the Athlon era VIA chipsets in PIO mode are that slow even without an adapter. You can try to load the VIA Bus Master(Ultra DMA) IDE driver from CONFIG.SYS to get better performance under DOS:

Copy code to clipboard

1DEVICE=C:\DOS\VIAIDE.SYS

The attachment VIAIDE.zip is no longer available

That does work in getting disk speed in DOS to UDMA levels, but it causes Windows to fall back to "compatibility mode" for drives. I suppose this is not optimal, especially as low disk speed in pure DOS is not that big of an issue?

Mike_ wrote on 2026-07-13, 18:48:

I tested it with HDTach and it does seem to work at about the speed you would expect from the IDE controller in Windows. […]
Show full quote

jakethompson1 wrote on 2026-07-13, 17:19:

UDMA is used in Win98SE (you can run SPEEDSYS HD from a Windows DOS box and get away with it and check the speed even though it admonishes you not to run it under Windows) while in DOS, the BIOS disk support generally falls back to PIO. Even then, it should not be this slow, although lack of Multiple Sectors Per Interrupt on most SSDs (assuming this SATA disk is one) hurts performance. There's no technical reason the BIOS couldn't use UDMA for Int 13h accesses, but PIO avoids having to implement VDS or triggering UDMA-related incompatibilities with picky drives.

I tested it with HDTach and it does seem to work at about the speed you would expect from the IDE controller in Windows.

The attachment hdtach.gif is no longer available

Falcosoft wrote on 2026-07-13, 18:27:

Actually the Athlon era VIA chipsets in PIO mode are that slow even without an adapter. You can try to load the VIA Bus Master(U […]
Show full quote

Actually the Athlon era VIA chipsets in PIO mode are that slow even without an adapter. You can try to load the VIA Bus Master(Ultra DMA) IDE driver from CONFIG.SYS to get better performance under DOS:

Copy code to clipboard

1DEVICE=C:\DOS\VIAIDE.SYS

The attachment VIAIDE.zip is no longer available

That does work in getting disk speed in DOS to UDMA levels, but it causes Windows to fall back to "compatibility mode" for drives. I suppose this is not optimal, especially as low disk speed in pure DOS is not that big of an issue?

You should have at least 2 CONFIG.SYS options for boot to normal Win98 and boot only to command prompt menu options.

1[MENU]
2menuitem=Win98, Windows 98 (Normal)
3menuitem=CmdOnly, Command prompt only
4menudefault=Win98, 5
5
6[Win98]
7
8[CmdOnly]
9DEVICE=C:\DOS\VIAIDE.SYS
10
11[COMMON]
12DEVICE=C:\WINDOWS\HIMEM.SYS
13DEVICE=C:\WINDOWS\IFSHLP.SYS

Mike_ wrote on 2026-07-13, 18:48:

That does work in getting disk speed in DOS to UDMA levels, but it causes Windows to fall back to "compatibility mode" for drives. I suppose this is not optimal, especially as low disk speed in pure DOS is not that big of an issue?

1. If "restart in MS-DOS mode" is sufficient for your needs and DEVLOAD or similar is compatible with this .SYS driver, you could try loading it from DOSSTART.BAT.

2. You could try listing it as a safe driver in c:\windows\ios.ini. Of course, if it is not actually safe, you could corrupt the file system and lose data.

To be honest, this isn't big enough of a problem that I'd want to bother with boot menu options. I'll probably want to run most DOS games from Windows' DOS box anyways, as then AWE64 can use Windows' drivers for general MIDI.

Mike_ wrote on 2026-07-13, 19:54:

To be honest, this isn't big enough of a problem that I'd want to bother with boot menu options. I'll probably want to run most DOS games from Windows' DOS box anyways, as then AWE64 can use Windows' drivers for general MIDI.

I think you'd find other good reasons to setup the boot menu beyond just the disk driver. If you intend to use pure DOS along with win98 it's pretty much required IMO

maxtherabbit wrote on 2026-07-13, 21:27:

I think you'd find other good reasons to setup the boot menu beyond just the disk driver. If you intend to use pure DOS along with win98 it's pretty much required IMO

I was just thinking to use restart to MS-DOS -option when a game doesn't run properly from Windows.

Mike_ wrote on 2026-07-14, 08:19:

maxtherabbit wrote on 2026-07-13, 21:27:

I think you'd find other good reasons to setup the boot menu beyond just the disk driver. If you intend to use pure DOS along with win98 it's pretty much required IMO

I was just thinking to use restart to MS-DOS -option when a game doesn't run properly from Windows.

My personal recommendation which is me-approved is to have a restart into MS-DOS shortcut with it's own self contained MS-DOS configuration (ala Phil's easy MS-DOS shortcut), you can load it with as much dos-specific stuff you want and it never affects 9x performance or capability.