General configuration notes for DOS, W98SE, and ISA-era BIOS

Last modified: Sun Feb 7 17:42:38 EST 2016

IRQs and DMAs for ISA cards
Award Modular BIOS
Phoenix OEM BIOS (Dell and Gateway)
USB legacy emulation
Multiboot considerations

IRQs and DMAs for ISA cards

At a minimum, a sound card is going to need one IRQ and one DMA to emulate a Sound Blaster.  The most likely choices are IRQ 5 and DMA 1.  Additional IRQs may be needed for native-mode sound, the MPU-401, and/or the CD-ROM interface (tertiary IDE or SCSI controller).  Additional DMAs may be needed for 16-bit sound, full-duplex operation, and/or the CD-ROM interface.

The standard fixed claims for 486 and newer PCs are shown in the table below.  Additional IRQs may be claimed by USB controllers, network devices, video cards, and IDE/SCSI controllers.  Additional DMAs may be claimed by SCSI controllers.  Resources can be freed up by disabling unneeded devices or tweaking PCI interrupt sharing in the BIOS.

IRQDMANormally claimed by
3Serial port COM2 (if present)
4Serial port COM1
62Floppy drive controller
73Parallel port
9ACPI (if present)
12PS/2 mouse port
14Primary IDE (1 cable 2 drives)
15Secondary IDE

Toward the end of the ISA era some motherboards gained I/O APICs which made it possible for PCI devices to use IRQs above 15.  This at least reduces competition for the low-numbered IRQs.

Award Modular BIOS, circa 1999

Standard CMOS Setup

Hard Disk Mode (Auto, Normal/CHS, LBA, or Large)

Always set it to LBA.  If left on the default AUTO it will use the weird "Large" (extended CHS) remapping scheme on some disks, which screws up LILO.

BIOS Features Setup

XX000-XXFFF Shadow (Enable or Disable)

I have not found these settings to have any impact on UMBPCI's ability to repurpose shadow RAM to create UMBs.  There seems to be no harm in leaving them all enabled.  If necessary, the addresses used by ROMs can be determined by probing with DEBUG in DOS.  They are pretty obvious in the hex dump.

Chipset Features Setup (VIA MVP3 version)

AGP-2X Mode

Enable!!!  (Worst BIOS default ever!)

SDRAM Cycle Length (2 or 3)

Set this to the CL (CAS Latency) of the DIMMs, or just say 2 if the DIMMs are rated for a higher frequency than the motherboard.

DRAM Timing (SDRAM 10ns, SDRAM 8ns, Normal, Medium, Fast, or Turbo)

The menu is mysterious, but Turbo seems to be a good choice.  I've never encountered a problem with PC133 DIMMs that was solved by twiddling this.  PC100 = 10 ns (reciprocal of 100 MHz); PC133 = 7.5 ns (reciprocal of 133 MHz).

Other more or less obscure speedup options available on this page seem to be mostly harmless.  Some clearly apply only to 72-pin SIMMs.

Chipset Features Setup (Intel 430TX version)

SDRAM(CAS Lat/RAS-to-CAS) (2/2 or 3/3)

Set this to the CL (CAS Latency) of the DIMMs, or just say 2 if the DIMMs are rated for a higher frequency than the motherboard.

Other settings

The horrible "Turbo" menu is gone, but this screen is still a cryptic mix of options that might be specific to either 168-pin DIMMs or 72-pin SIMMs.

PNP/PCI Configuration

PNP OS Installed

Yes:  The BIOS will initialize mainboard devices, PCI and AGP cards but not ISA PnP cards.

No:  The BIOS will also attempt to initialize ISA PnP cards.  This is a desperate way to maybe get a PnP card to work when you have no drivers for it.

Resources Controlled By

If the BIOS is grabbing IRQs or DMAs that are needed, set this to Manual and then change the assignments for those resources from PCI/ISA PnP to Legacy ISA.  A setting of Legacy ISA is just a reservation to prevent the BIOS from grabbing a particular IRQ or DMA for the devices that it initializes.  It has no effect on initializations of PnP cards by DOS or W98SE drivers.

Assign IRQ For USB

If not using the USB headers on the motherboard, disable this to reduce IRQ contention.

Integrated Peripherals

Onboard Serial Port 1/2 and Parallel Port

Disable unneeded serial and parallel ports to free up three IRQs and one DMA.

IDE Prefetch Mode and HDD Block Mode

If BIOS is used at all for disk access, these options will do something.  Block mode is always good, but prefetch might be redundant.

Phoenix OEM BIOS (Dell and Gateway), circa 1999–2000

The following are all under the Advanced tab.

Plug & Play O/S

Yes:  The BIOS will initialize mainboard devices, PCI and AGP cards but not ISA PnP cards.

No:  The BIOS will also attempt to initialize ISA PnP cards.  This is a desperate way to maybe get a PnP card to work when you have no drivers for it.

Peripheral Configuration

Disable unneeded serial and parallel ports to free up three IRQs and one DMA.

Resource Configuration

IRQ 3/4/5/7/10/11 (Available or Reserved)

A setting of Reserved prevents the BIOS from grabbing a particular IRQ for the devices that it initializes.  Note that IRQ 9 is permanently grabbed for ACPI and there's no menu to reserve DMAs.

Shared PCI IRQs (Auto, Share One IRQ, Share Two IRQs, or Share Three IRQs)

If set to Share One IRQ, all PCI and AGP devices share IRQ 9.  On Auto, all non-reserved IRQs get grabbed.  This option did not appear on the Dell (1999, PhoenixBIOS 4.0 Release 6.0).

USB legacy emulation

USB legacy emulation (a BIOS feature) is necessary for a USB mouse or keyboard to be visible in plain DOS (not yet tested:  USBDOS driver), W98SE Safe Mode, and the early stages of W98SE installation.

If the motherboard has just one PS/2 port that supports either keyboard or mouse, let the mouse have it.  Legacy emulation is more likely to work right for the keyboard.

N.B., PCI cards that add PS/2 ports don't work without drivers.


The relevant flavors of DOS are FreeDOS and occasionally MS-DOS 7.1 (FORMAT /S of W98SE).  See empirical comparison of candidate DOS kernels (98SE, ME, FreeDOS).

Partitioning and formatting

I'm currently using W98SE FDISK to get partitions that work with everything (i.e., no complaints from FreeDOS, W98SE, or LILO).

FreeDOS's FORMAT will sometimes crash when attempting to save unformat information.  To avoid this, do FORMAT /S /U C: and then hit ESC at the first opportunity to skip the pointless overwriting of the entire partition.

Memory management

NOTE:  For MS-DOS, adding AUTO after UMB on the DOS= line will move DRIVEDATA to the UMA, but will also attempt to automatically load HIMEM.SYS, IFSHLP.SYS, DBLBUFF.SYS, and SETVER.EXE if they exist.

Option 1:  Virtual 8086 mode with VCPI

JEMMEX (in JEMM package) provides the functionality of HIMEM.SYS + EMM386.EXE together in a single driver.  Although real mode is generally preferred for game performance, some PCI sound card drivers require the EMM.


Option 2:  Real mode with XMS, HMA, and UMBs

UMBPCI followed by XMGR (in "drivers" package) provides XMS, HMA, and UMBs in real mode on supported chipsets.  This is the best option if it works, but UMBPCI causes a slowdown on chipsets where UMBs are not cacheable (e.g., MVP3) and does not work at all on some chipsets.

Much is said in the UMBPCI documentation about how some chipsets don't allow DMA to UMBs, but this seems to matter only for SCSI drives and for TSRs that cache the floppy drive.


Option 3:  Real mode with XMS and HMA

Just XMGR is enough to get DOS loaded high.


IDE driver/cache

All three of the following options need SHSUCDX in AUTOEXEC.BAT as follows:


Option 1:  UIDE

When it works, UIDE speeds up HDD access using Ultra DMA, provides disk caching, and handles CD/DVD drives, all in one efficient driver.  Unfortunately, it causes lockups with many sound cards and has other complications.

I have found that loading UIDE into UMBs provided by UMBPCI may lead to spontaneous reboots or lockups when protected-mode games are running.  (Problems occurred on two different 440BX motherboards, one Dell one Gateway, with UMBPCI v3.85 and UIDE rev. 2015-03-05.)  Since UIDE needs only 5 KB of RAM, just load it low.  (With the W98SE kernel, most of that 5 KB is moved to the HMA; not sure why this doesn't work with FreeDOS.)

Accepted values for UIDE.SYS /S cache size (from README.TXT):  5, 15, 25, 40, 50, or any number from 80 to 4093 (MiB).


Option 2:  UIDE /E

/E tells UIDE to use BIOS calls to access drives.  This avoids lockups in some cases but not others.


Option 3:  UDVD2

UDVD2 is a basic DVD-ROM driver that has never conflicted with anything.







Long filename driver

DOSLFNMS was the one that worked.  Its downside is that disk caching is essential to avoid a major slowdown.


Mouse driver

CTMOUSE works with all normal serial and PS/2 mice and never conflicts with anything.


CPU idle

In FreeDOS, just put IDLEHALT=1 in CONFIG.SYS.  For MS-DOS, FDAPM.



For specific sound card details, see ISA or PCI.

MS-DOS 7.1 / W98SE tweak

To avoid unnecessary splash screens and logs, install the following in the root directory as MSDOS.SYS:




W98 is a single-CPU operating system.  Additional cores provide no benefit.  The last single-core CPUs in Intel's desktop category were the Prescott Pentium 4 series.  However, running on one core of a multi-core CPU does work.

W98 has a host of problems with systems that have more than 512 MiB of RAM.  There are workarounds, but if the PC is being configured for W98 and compatible 128/256/512 MiB DIMMs are available then it's preferable to limit the amount of RAM.

W98 has another host of problems related to hard disk size and partitioning.  It is absolutely unable to access anything beyond the 128 GiB limit of 28-bit LBA, and it is unlikely to play nicely in a partition that was defined by Linux fdisk.

W98 works with SATA drives and SSDs, but often it is necessary to configure the SATA controller for "Legacy Mode," "Compatible Mode," or "IDE" rather than "Native Mode," "Enhanced Mode," or "AHCI" in order to get through the installation process.  Once installed, it may continue working if AHCI is re-enabled.

Whenever W98 complains that it can't find a file and pops up a dialog box to let you locate it, the place to browse to is either the WIN98 directory of the installation CD or the directory from which you are trying to install something.  It will generally pick it up even though it's buried in a CAB file.


If maximum patching up is desired, there is an unofficial service pack maintained by PROBLEMCHYLD, or see the ostensibly complete list of hotfixes & updates for Windows 98SE on MSFN.  See also, tons of miscellaneous stuff from MDGx.  The following is my short list.

Partitioning and formatting

W98SE must reside entirely within the first 128 GiB (137 GB) of the hard drive to avoid overflowing its 28-bit LBA implementation.  Setup is basically wack when it comes to large disks, so run FDISK and FORMAT manually before entering it.  Use the patched versions noted above and ignore any incorrectly printed sizes.


Various disk-trashing misbehaviors can occur if one does not walk on eggshells around W98 FDISK and FORMAT.  Repartitioning (as opposed to creating a new partition table) should always be done using Linux fdisk, never a Windows installation CD.  Windows will trash your partition table every time.


Installation process

After launching setup, just continue past the warnings about there already being an OS in the partition, and about NT file system.  Any unrecognized partition type is assumed by setup to be NT.

When setup finishes its first phase, you are instructed to remove the floppy (meaning take the CD out) and reboot.  Setup has already clobbered the MBR, so when you reboot you enter the GUI portion of setup.  It is at this point that memory size hacks become necessary if 1 GiB or more of RAM is present.

Two reboots later, W98SE's hardware wizard is busy installing drivers.  You have to humor it until it goes away.  Even when it has no driver for a particular device, it must be allowed to search for it; if you just cancel out, the dialog will come back again every time you reboot.

Memory size hacks

W98SE fails in a variety of ways when more than 512 MiB of RAM is installed.  Usually the error says "Insufficient memory" or "There is not enough memory available" or some such ass-backwards shiat.

The free workarounds for the most obvious failures are described below.  There also exists a third-party binary patch, but as of 2014 it was still being aggressively defended as commercial intellectual property.  Probably no solution is going to be perfect except for physically reducing the amount of RAM.

SYSTEM.INI configurables

Add the following settings to WINDOWS\SYSTEM.INI per kb184447 and kb253912:



All numbers are subject to adjustment, as the interactions are weird and the best numbers depend on the actual amount of RAM installed.  MaxPhysPage is a count of 4 KiB pages in hexadecimal, so 30000 means 768 MiB and 40000 means 1 GiB.  MaxFileCache is kB in decimal, so 131072 means 128 MiB.

HIMEM workaround

In CONFIG.SYS, load HIMEMX.EXE, maybe with /MAX=523264 to limit XMS to 511 MiB.

The HIMEM.SYS that W98SE loads automatically is just bugged and unstable when there is a lot of RAM.  Loading HIMEMX first keeps it from loading that.  The /MAX switch works around subsequent problems resulting from too much memory.

XMGR.SYS might be as good but it does not have the memory-limiting option.

General drivers (excluding sound, video, and add-in cards)

CPU idle driver AMNHLT (

AMNHLT appears to be redundant if ACPI is enabled.  I did not notice a wattage drop after installing it on a P4 PC.  According to this forum post, in case the regular installation fails to enable ACPI, setup /p j forces it.

To install AMNHLT, run the batch file.

VIA chipset drivers

4in1 4.43 for older chipsets, Hyperion Pro 5.24A for newer ones.

Maximus Decim Native USB drivers

These drivers include INF.  Intel or VIA INF may prevent them from working, as will any previously installed drivers for USB cards.

  1. Go into device manager (right-click on My Computer, Properties, Device Manager tab) and Remove all USB hub devices ("USB Root Hub").  Do not reboot yet.
  2. Install NUSB.exe.
  3. Reboot and let it reinstall the USB hubs using the new INF.
  4. USB drives and whatever should now work just like in XP.


Sound drivers can be either VxD or WDM.  Microsoft's GS softsynth only works with WDM drivers.  However, all WDM sound drivers cause glitching of sound effects in DOOM.  kb242937 does not fix that.

The MS softsynth is legitimate Sound Canvas.

Commonly, the only mixer will be hidden underneath the Microsoft volume control in the bottom right corner of the screen:  single-click the tiny icon for volume, double-click it for the mixer.

For specific sound card details, see ISA or PCI.


If no good vendor drivers exist, W98's plain old "Standard PCI Graphics Adapter (VGA)" driver usually works.  However, it is limited to 640×480 16-color mode and is slow.  In my experience, it is reliable across a broad range of video cards, including older PCIe ones, but with a GTX 970 it produced glitched graphics.

A PCIe GeForce 8500 GT connected via DVI responded acceptably to the "Standard PCI Graphics Adapter (VGA)" driver, but for some reason felt the need to put a thin black border around the entire screen.

The VBEMP 9x Universal VESA/VBE Video Display Driver (or here) works on a similar principle.  It too is slow, but unlike the Microsoft driver it allows access to high resolution, true color modes supported by the video BIOS.  It worked without glitching at 1920×1080 32 bpp on the GTX 970.  To install it, navigate through device manager or right click on desktop → Properties → Settings → Advanced → Adapter to the current display driver, choose Update Driver or Change, navigate some more through to "Have Disk" and "Browse," and browse to the 128MB directory of the VBEMP distribution.

Milestones in Nvidia Windows driver version history:

96.85 Last "ForceWare" drivers.
93.71 Last Windows version "supporting" GeForce2 MX, GeForce3, and GeForce4.
81.98 Last version supporting Windows 98 SE.  Does NOT work with TNT2 64.
77.72 Last W98 version in the 7x series.  Does NOT work with TNT2 64.
72.14 Last Windows version "supporting" GeForce 256 and non-MX GeForce 2.
71.89 Best Nalu benchmark under Windows XP.
71.84 Last W98 version prior to 72.14.  Last W98 version that works with TNT2 64.
66.94 Last W98 version in the 6x series (no release notes).  Works with TNT2 64 (PCI) and TNT (AGP).
61.76 First Windows version to support 6800 series GPUs.
56.72 Last Windows version that "supports" Vanta and TNT2.
56.64 Last W98 version in the 5x series.  Did not work with TNT (AGP).
53.04 Last Windows version that "supports" TNT.
45.23 Last "Detonator" drivers (allegedly better for old GPUs).  DID NOT WORK with TNT (AGP):  "unable to locate a detected device's PCI ID in NVAGP.INF."

GPU "support" was determined from the release notes.  The User's Guide for 66.93 still claims support for Vanta, TNT, and TNT2.  Neither the release notes nor the users guides are correct—when tested, a TNT2 64 actually worked up through version 71.84!

Nvidia's official support for W98 ended with the GeForce 6 series GPUs.  Maximus-Decim's modded 82.69 drivers supposedly work some of the time up through the GeForce 9 series, but they didn't work for me.

When DOOM running in a DOS box tries to switch to full-screen 320×200 mode, Nvidia drivers often give a black screen (maybe just with LCD monitors?).  The standard VGA driver and the VBEMP VESA driver don't have that problem.

The 71.84 and 81.98 ForceWare drivers did not render 640×400 mode correctly for DOOM 95.  Versions 12.41, 53.04 and 66.94 all worked.

Image quality in 640×400 mode is improved by checking the box NVIDIA Display → Display Mode Timing → Enable doublescan for lower resolution modes (if it exists in the version used).

For some versions, EnableRefreshRateLock.reg is needed to enable setting a non-default refresh rate that will stick within games.

Almost unattended installation

As described here and here, most installation prompts can be pre-configured using a batch tool that is provided on the W98SE installation CD (under tools\reskit\batch).  Burn the resulting msbatch.inf file into the WIN98 subdirectory of the installation CD and most prompts go away.  It still has a few nits:

To get rid of the task scheduler, run msconfig, select Startup tab, uncheck Scheduling Agent, reboot.

Other install CD tweaks

The W98SE install CD's boot image has this in CONFIG.SYS for both the SETUP_CD and CD menu options, which makes for a slow and messy boot:

device=himem.sys /testmem:off
device=oakcdrom.sys /D:oemcd001 
device=btcdrom.sys /D:oemcd001
device=aspicd.sys /D:oemcd001

Replace that with this:

DEVICE=UDVD2.SYS /H /D:oemcd001


REM LH MSCDEX.EXE /D:oemcd001 /L:D
REM We haven't loaded any UMB provider, so LH is useless.
SHSUCDX.COM /C /D:oemcd001 /L:D

This only affects the environment for Setup.

Dropping the patched FORMAT.COM and FDISK.EXE into the WIN98 subdirectory of the installation CD apparently causes these versions to be installed automatically.

TBD:  CAB edits to reduce the amount of post-install patching that is required.

Installing as plain DOS

Using W98SE as a version of plain DOS is actually much easier than getting it to work in Windows mode.  DOS has no failures triggered by memory over 512 MiB and will use BIOS calls for disk access.

  1. Prepare a partition and format it as described previously.
  2. Manually copy in any desired binaries and set up AUTOEXEC.BAT and CONFIG.SYS to taste.

FreeDOS has a better installer and bundles superior, enthusiast-maintained replacements for many of the DOS programs that come with W98SE.  As a compromise, one can take the kernel, COMMAND.COM, FORMAT.COM, FDISK.EXE, and SYS.COM from W98SE for better MS-DOS compatibility, but throw out everything else and use free replacements.

Multiboot considerations

If you installed Linux before W98, you will need the Linux install CD or an emergency boot something to get you back into Linux to reinstall LILO or GRUB after W98 does its damage.  Alternately, you can back up your MBR before installing W98 and then just restore it afterward.

Every version of Windows insists on owning the C: drive, so some workaround is always needed to get two Windows installations to coexist without jumbling their system files together in the same partition.  The easiest way to get XP and W98 to be good neighbors is to exploit the fact that W98 ignores NTFS partitions.  If you put XP on NTFS in the first partition and put W98 on FAT32 in the second partition, then each OS will see its own partition as the C: drive.  If for some reason this approach is unusable then you will have to fall back to more drastic options such as hiding and unhiding partitions or remapping drives at boot time.  N.B., even when the NTFS partition comes first, if XP is allowed to see W98's file system it will activate System Restore on it and create a subdirectory called System Volume Information in the root directory.  So while it is not strictly necessary to do so, you might want to hide the W98 partition just to keep the taint of XP off of it.

If you run Linux, it is generally easier and more reliable to boot W98 and/or XP using LILO or GRUB than using Microsoft's own boot loader.  LILO and GRUB support partition hiding and drive remapping if you should need those features.  On the other hand, the XP boot loader provides access to XP's safe mode.

The XP boot manager can be used to boot a W98 and/or Linux partition by following the example in the antiquated but still mostly accurate NT OS Loader + Linux mini-HOWTO (v1.11, 2 September 1997).  Copy Microsoft's boot sector (instead of a LILO boot sector as described in the HOWTO) from the W98 partition to a file on XP's C: drive and reference it in XP's BOOT.INI file:  C:\W98.BIN="Windows 98 SE".

Please note:

Nowadays, modern BIOSes include their own multiboot menus that are launched by hitting a hotkey during POST.  When things get out of hand, you can install a different boot manager on every disk and use the BIOS menu to choose among them.