Phoenix OS/4

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Phoenix 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.


Installation instructions

From now, we assume that you downloaded the latest OS/4 kernel distribution zip file, and it is named like this:, where xxxx is the SVN revision of the downloaded release. To clarify the following installation instruction, it is assumed, that the downloaded distribution file's name is Please, rename the downloaded file to using your favorite filemanager or the CMD.EXE's ren command like this: ren Also, you will need the unzip utility, which you can find on hobbes. A more up to date (capable of handling files larger than 2 GB) version can be found at Paul Smedley's OS/2 ports site

Okay, so everything is prepared -- let's begin!

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, CONFIG.SYS editor which may be invoked right before the kernel loads (available on OS/4 kernels only; although the modified version of the config is not put back on the disk, the feature is fairly useful in crash recovering), chainloading another kernel bootloaders and preloading files in the memory (better boot time).

So, the first thing to do, is to install the OS/4 kernel bootloader, because the original one is unable to load the OS/4 kernel. If you use a recent version of ACPI, original kernel, or both (you have eCS), then it is highly recommended to keep the original bootloader:

  • unset the hidden attribute of the original kernel bootloader: attrib -H \OS2LDR
  • rename OS2LDR to OS2LDR.IBM: ren \OS2LDR OS2LDR.IBM
  • extract OS2LDR from the OS/4 package to the root of the boot drive: unzip OS2LDR -d \

Then extract the Phoenix OS/4 kernel to the root of the boot drive (the file is named OS4KRNL for the debug version and OS4KRNLR for the retail version):

  • we will use the retail version, so do unzip OS4KRNLR -d \.

OS/4 ships also with an updated DOSCALL1.DLL library, which works fine with both kernels (highly recommended):

  • download the lxlite package from hobbes (eCS already has this tool, although there is some argument about the way that it works. Any version should do what is necessary).
  • extract the unLock.exe utility to your PATH, for example, to the \OS2 directory: unzip -j lxLite\unLock.exe -d \OS2
  • now unlock your current DOSCALL1.DLL file: unlock \OS2\DLL\DOSCALL1.DLL
  • rename it for a backup: ren \OS2\DLL\DOSCALL1.DLL DOSCALL1.IBM
  • and then extract the Phoenix version: unzip os4krnl_current DOSCALL1.DLL -d \OS2\DLL

Then you need to configure the OS/4 kernel bootloader to be able to load the original, and the Phoenix kernel. The configuration file's name is OS2LDR.INI. An example configuration file is present in the distribution package, and contains a comment for each line. Note that this is a TEXT file, not a binary INI file.
Create an empty OS2LDR.INI file in the root of the bootdrive and then put this in it using a text editor (or whatever you want):


OS2LDR.IBM = IBM orig. kernel ,RESTART
OS4KRNLR   = Phoenix kernel   ,PRELOAD

The default statement in the config section sets the default selection in the kernel selection menu, and the timeout statement sets the time in seconds before the default kernel will be loaded.
In the kernel section, the statements must comply with the following syntax:

<kernel or loader filename> = <kernel selection menu option text>[,option[=value][,option[=value][,option[=value][...]]]]

The possible options are:

RESTART Indicates, that the file to be loaded is an another kernel bootloader, rather than a kernel file.
LOGSIZE Defines the size of the log buffer (which you can get reading special device files) in KiB (0 < value < All memory - 16MiB).
PRELOAD Use the files preload function (a must for OS4APIC to work properly, also speeds up the loading process).
LOADSYM Try to load the symbol files (useful for debugging).
CFGEXT Specifies an extension for the CONFIG.ext file to be loaded instead of the CONFIG.SYS file, where ext

is the extension specified by the CFGEXT statement (must be three characters or less).

ALTF1 Emulates a user pressing Alt-F1 in the loader menu.
ALTF2 Emulates a user pressing Alt-F2 in the loader menu.
ALTF3 Emulates a user pressing Alt-F3 in the loader menu.
ALTF4 Emulates a user pressing Alt-F4 in the loader menu.
VALIMIT Set Virtual Address Limit

Although the original kernel may be loaded by the OS/4 kernel bootloader directly, the most stable configuration is to use original bootloader to load the original kernel.

Notice, that the original bootloader (OS2LDR.IBM) is able to load only the kernel file, named OS2KRNL, and you have to keep the original kernel with that name to have the ability to load it with the original bootloader.

Also notice, that although you have the ability to chainload kernel bootloaders with custom name using the Phoenix bootloader, the first loaded kernel bootloader is always named OS2LDR.

There are also some configuration statements you can use in the config section in the Phoenix bootloader configuration file, but those are usually only useful for debugging and troubleshooting purposes. See the example OS2LDR.INI file in the OS/4 kernel distribution package.

This is a basic installation process, but remember, that there is also a new CLOCK03B.SYS, which supersedes original TIMER0.SYS and CLOCK01.SYS drivers. It is recommend to install this driver:

  • unzip CLOCK03B.SYS -d \OS2\BOOT

You don't need to modify CONFIG.SYS

Attention! Since SVN revision 4166, it is mandatory to install the new SCREEN03.SYS, otherwise kernel won't boot:

  • unzip SCREEN03.SYS -d \OS2\BOOT

You don't need to modify CONFIG.SYS, too.

Okay, everything is set up. Now reboot your system!
You should notice the kernel selection menu with two options, where you can select to load either the original IBM kernel, or the Phoenix one. Although you may fail to boot up with the Phoenix kernel due to a bug in it, there is no doubt you will be able to fall back to the original kernel and boot your system with it (if you were able to do this before :) ).

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
Lenovo Thinkpad X61s (Mainboard 766736U) Barbara 06/09/2016 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.

Frequently asked questions

Q: I'm getting a SYS1195: The statement "VIRTUALADDRESSLIMIT" on line *** of the CONFIG.SYS file is not recognized. Line *** is ignored.

error message while booting. What's wrong?

A: Somewhere in SVN3xxx the VIRTUALADDRESSLIMIT tuning feature was broken. Now the VAL is fixed and set to 2048.

There's nothing bad in the error message; you can REM or remove the entire VAL statement in your CONFIG.SYS file -- it will always remain fixed to 2 GiBs.

Unfortunately, there is no information whether Phoenix will fix this issue and make the VAL changeable again, or not.

Q: Can I use ACPI.PSD with the OS/4 kernel, and what version?
A: Yes, you can. The best option is to use the 3.18 version, as that's the latest officially supported version, and it has recommended itself as the most stable ACPI.PSD.

Q: I'm getting a TIMER0.SYS... initialization failed error message while booting. What's wrong?
A: The 16-bit TIMER0.SYS driver fail is okay because its function is now fully substituted by the CLOCK03B.SYS system driver written by Phoenix.

Q: What is the purpose of the CLOCK03B.SYS driver?
A: The CLOCK03B.SYS was rewritten in 32-bit and now contains two drivers: CLOCK$ and TIMER0$ (having more than one driver per module is allowed in OS/2). That was made for better performance and code cleanup.

Q: Does CLOCK03B.SYS driver recognize the CLOCKSCALE CONFIG.SYS option?
A: Yes, it does. More information about CLOCKSCALE by ConfigTool:
 =n (n=1,2,4)
 New setting, needs clock01.sys delivered with kernel 14.080a
 The theory is that CLOCKSCALE=4 will speed up some apps (maybe Netscape and/or Java).
 <<=NOTE=>> By Robert Lalla:
 Multithreaded GUI applications are required to switch frequently between threads, for quick response to user input and fast screen updates.  For native OS/2 applications there are available plenty of OS/2 kernel functions (semaphores, priorities, etc.) to allow  thread switches at any required speed. Java programs and many software ported from other OS do not make much use of those kernel functions, maybe because they simply expect the cpu time to be shared among threads using very short timeslices.
 OS/2 has also timeslices, intended for applications that don't want to share cpu with other applications. The standard timeslice was 32ms (or multiples depending on CONFIG.SYS) since early 6 MHz 80826 days. In more recent versions of OS/2 the scheduler's timer is running at 8ms, but I'm not sure if standard priority applications could profit from.
 The purpose of "clockscale" is most likely to shorten minimum timeslices by a given factor, down to 2ms.

Q: What is the purpose of the SCREEN03.SYS driver?
A: The SCREEN03.SYS was written to enable Panorama VESA BIOS Extension Video Driver to set the proper Write-Combine flags for the LFB (the linear frame buffer) without ACPI.PSD.

Now the Phoenix team provides the full alternative to the OS2KRNL + ACPI.PSD + PANOGRADD stack of technologies:


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.


Known problems and not-a-problems

  • Tracing (STRACE and TRACE) feature is discontinued. Phoenix team is not going to make it work again.
  • The current way to display bootlogo is very outdated, poorly written, and the maximum color depth is only 8-bit (256 colors), so Phoenix decided to rewrite this part. The new way to show bootlogo is not ready yet, and the old one is broken. Await the new bootlogo in future releases.

I think there is a bug in the kernel...

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).

To turn on debugging over COM port, set the following setting in the config section of \OS2LDR.INI:


Important thing: you should use the debug kernel to get the log, so extract the debug kernel file to the root of the boot drive:

unzip OS2KRNL -d \

and modify the kernel section of \OS2LDR.INI to be able to load it.

Anyway you would like to try the debug one, because the retail kernel may have some bugs already fixed in the debug one, so if you encounter any problems, please try the debug one.

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.

Now, if your system traps, the trapscreen will be sent over the COM port, and the Kernel Debugger command promt will appear:


You can try entering the question mark in terminal -- the Kernel Debugger (aka KDB) will show you the help screen. The most useful command for a user is .reboot ;)

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. So, for OS4KRNL, put OS4KRNL.SYM in the root of the boot drive:

unzip os4krnl_current OS4KRNL.SYM -d \

If the name of the debug kernel you load differs from OS4KRNL, rename the symbol file to correspond to its name:


where KERNNAME is your current custom name for the kernel.

Now, to make the kernel to try to load the symbol files, add the LOADSYM option to the kernel setup string in the kernel section of \OS2LDR.INI.

So, if you don't have at least one COM port, there are still some possibilities: ...

TODO: Write this section. Dbanet (talk) 19:44, 3 April 2014 (CEST)

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.

Submitting the bugreport

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

Currently, the download section on the RU/2's Core/2 is outdated (will be fixed ASAP).

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.

Also the first post on the OS2World thread about OS/4 should contain the direct link to the release.

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 section on the Russian Underground/2, fully devoted to the Phoenix project (Russian only).
[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 Phoenix is to join the #os2russian IRC channel on the original EFNet network.

There is no collaborative e-mail mailbox, but you may consider writing to the SU.OS2 Fidonet area... Hrm. Well, the IRC channel is the best option.

Also there is a technical forum at the Russian Underground/2, where you can try writing to, too.

Most of the dialogs in the IRC channel, RU/2 forum, or the echo conference 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.