Phoenix OS/4

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OS/4 is a research project intended to recreate the original kernel for the IBM Operating System/2. The main goal of the project is to make the system able to work on the PCs, that it is unable to work on with the original kernel.


Download the latest OS/4 kernel distribution zip file which is named like this:, where xxxx is the SVN revision of the downloaded release and perform the HowTo from this archive.

The OS/4 distribution package includes a powerful kernel loader, which features loading OS/4 and OS/2 kernels, kernel selection menu, custom CONFIG.SYS files for each kernel.

OS/4 technical notes

Video bus bandwidth (VBB)

VBB is a factor which end users feel like speed of video system output. Everyone can check the value of VBB using a well known tool - SYSBENCH.

To have an acceptable VBB, the LFB (linear frame buffer) of video card has to be mapped with WC (write combine) type of caching.

x86 provides 2 ways of setting WC for memory regions (LFB is actually a memory region):

1) using MTRR registers.
2) using PAT extension.

OS/4 is using PAT to set WC for LFB. For this propose OS/4 offers new KEE entry: KernVMAlloc2 - the same as KernVMAlloc but with a new parameter - type of caching.

So we need to intercept all the requests for mapping LFB and route them to KernVMAlloc2 with an explicit indication of the type of caching (WC).

It appeared that OS/2 uses many different ways to map LFB:

  4. XFree86/OS2 - >xf86sup.sys

Thus solutions from OS/4 are:

  1. rewritten SCREEN$ and SINGLEQ$ (SCREEN03.SYS and PMDDk.SYS correspondingly).
  2. a patch for DIVE.DLL to call SCREEN03.SYS but not SMMDD.SYS.
  3. rewritten SDDHELP.SYS.
  4. not yet done (need rewrite of xf86sup.sys or caller in XFree86/OS2).

OS/4 Tested Hardware List

Model Reporter Date of Report Remarks
Asus P5B-Delux OS4user 04/11/2015 everything works ok.
Tyan Toledo i3210W OS4user 21/03/2015 everything works ok.
Gigabyte GA-B75M-D3V Joseph 13/04/2015 sound card does not work ok
Asus P8Z77-MPRO Joseph 13/04/2015 sound card does not work ok
Gigabyte GA-H61M-S2PV Joseph 13/04/2015 sound card does not work ok
Gigabyte GA-EG41MF-US2H Digi 14/04/2015 power button does not work, Shutdown from XCenter causes reboot.
Gigabyte GA-H61M-S2PV 1 Digi 14/04/2015 everything works ok
ThinkPad T410 Sergey Posokhov 14/04/2105 everything works ok
ThinkPad T61 Codex 14/04/2015 everything but /APIC
Gigabyte GA-F2A88X-D3H ff4 27/06/2014 sddhelp.sys from os/4 needed
Asus P5E3 WS PRO Igor Vaskov 15/04/2015 everything works ok
Asrock Q1900B-ITX Igor Vaskov 15/04/2015 everything works ok
Gigabyte GA-B85M-D3V Joseph 28/04/2015 sound card does not work ok
Asus F2 A55-M MichelPB 20/04/2015 everything works ok
Asus M5A-99x EVO MichelPB 03/12/2014 tested only
Asus M4A87Td/USB3 MichelPB 16/05/2015 everything works ok
IBM Thinkpad T23 Barbara 20/05/2015 everything works ok
VMWare vSphere 5.1 (ESXi) Digi 23/06/2015 everything works ok.
Asrock A785GMH/128M MichelPB 08/07/2015 everything works ok.
Gigabyte GA-A75M-S2V MichelPB 27/08/2015 works ok(sound is not tested).
ECS KBN-I/2100 fighter4 16/12/2015 works ok(sound is not working).
ThinkPad X220i Oxyd 17/07/2016 everything works ok.
Lenovo Thinkpad X61s (Mainboard 766736U) Barbara 06/09/2016 everything works ok.
Asrock X370 Professional Gaming with AMD Ryzen 1700X CPU Yoda 26/06/2017 8 cores 16 threads working. No sound, no USB, no LAN/Wlan
GigaByte H110M-S2H David McKenna 09/09/2017 Starting with 4974, everything works ok. Need acpi4.bpd. USB3 only.
IBM ThinkPad W530 TeLLie 10-04-2018 All works, except power-off doesn't work.

Frequently asked questions

Q: Can I use ACPI.PSD with the OS/4 kernel, and what version?
A: Yes, you can. But with some restriction:
1) The latest supported version of ACPI.PSD is 3.23.01
2) ACPI.PSD has to be patched (the patch is available for 3.22.03, 3.22.06 and 3.23.01 versions of ACPI.PSD)
3) PSD= line has to contain a switch /ST=0 (for ex. PSD=ACPI.PSD /ST=0)

Compatibility with the latest ACPI.PSD can be easily reached if ACPI.PSD developers wish for it.

Q: How can I prevent the debug version of the kernel from jumping into KDB when some program traps?
A: Put this in KDB.INI file in the root of your boot drive:
.b 115200t

Q: How can I get the kernel log if my test PC does not have a COM port? Can I use a USBCOM device?
A: No, you cannot get a kernel log using a USBCOM device. For more information on getting the kernel log, please refer to the Troubleshooting/Getting the log section.

Also in case the system is successfully booted you can get the log by typing:

copy kernlog$ my_kernellog [enter]

Q: Can I edit config.sys (config.os4) on system boot?
A: Yes, you can. Press Alt-E when you see boot menu, after menu selection you will go to config editor. Note that changes will affect the current boot only and will not be saved to the disk.


Getting the log

The traditional way of getting the kernel log (and the only way now to remotely debug it), is to connect a terminal (a PC) to the COM port. You will need a terminal program on the other side (I suggest using DTerm) set up to work on the speed of 115200 baud, bits 8n1 and no flow control.

If your debug PC (the one which kernel's log you want to get) doesn't have a COM port, then there's a note at the end of this section for you. If your debug PC has one COM port, it is likely to be the COM port number one and have the 0x3F8 address, so put this setting in the config section of \OS2LDR.INI:


If your PC has more than one COM port, ensure you're using the first one for debugging, or, if not, fix this, or set the proper address for the COM port you use, like 0xEC00 for second COM port (you can see the addresses in your BIOS, or you can use the OS/2 Hardware Manager for that).

Important thing: you should use the debug kernel to get the log.

This is already enough to get the kernel log, so you may just fire up the terminal program and load the debug kernel when you're all set up. Please note, that the log is big enough to not fit in the console window, so you would like to turn on the logging feature in your terminal program (Control-L in DTerm).

Additionally, if you have a full COM cable, you may try putting fullcable=1 in the config section of \OS2LDR.INI, and turning on the hardware flow control in the terminal program (Control-F in DTerm) -- it helps if you notice missing characters in the log.

Also, if you reported a bug, you may be asked to trap the system and enter some commands for the KDB into the terminal, and show your output to the kernel developer. For some KDB commands to work properly, you need the symbol files (at least of the kernel) to be loaded. The symbol files must be in the root of the boot drive, or in the same directory of the program the symbol file is generated for.

Getting the Log from Command line

If you are able to boot OS/2 with the OS/4 kernel you can also generate the log to a file with this command:

 copy kernlog$ my.log

It will create the my.log file with the information.

Participating in testing

Testers are highly appreciated. By testing our kernel, you are helping the whole OS/2 community to make OS/2 runnable on every PC in the world. To begin testing, just take the latest debug kernel and try to run it on every PC you can see.

If you didn't run into problems, -- hooray! -- but if you did, that's why there is the #Troubleshooting section...

Getting the binary distributions

The latest kernel distribution should reside on the server in the /os4 directory.

You should find there a ZIP file in the root, starting with os2krnlSVN.

Resources on the WWW

[1] is an official HTTP server, where you can get the latest OS/4 kernel releases and some useful utilities.

[2] is a thread on the OS2World forum for technical support.

[3] is an IRC channel where you can get support.

[4] is a thread on the OS2World forum about OS/4.

Contacting developers

The most easy way to contact OS/4 Team is to join the #os2russian IRC channel on the original EFNet network.

Most of the dialogues in the IRC channel, RU/2 forum are performed in Russian, but if you jump there in English, you will get a conversation.

Also there is a thread in the OS2World forum (which is in English), where you can get support, too.