The Omnibook 600: Cute but Quirky


At 3.8 pounds, the HP Omnibook 600 is one of the smallest computers that one might reasonably want to run Linux on. It's smaller than many textbooks and you might well forget it's in your backpack. The lightest Pentium notebook is over 20% heavier; many notebooks are twice its size. It has a 75MHz 486DX4 processor, a beautiful (though small) screen, a great keyboard, and a reasonable pricetag (for a subnotebook). HP has a long-standing reputation for reliable hardware.

However, like all HP products, the Omnibook 600 has quirks. A couple features don't work under Linux and, until recently, Linux could not be installed in the obvious way. However, the dark rumors that have spread across the net are unwarranted: all the critical components work nicely. Some of the Omnibook's limitations might be fixed with further hacking and others can be worked around.

This is a machine for someone who values small size, and can live with its limitations. Read the details below and judge for yourself.


This page has no official connection to HP. Additional information about HP products can be found on the HP home page, though sadly their web site still has very little information on the Omnibooks.

Many people have helped us obtain this information and get Linux going. We would particularly like to thank Paul Henning, Pat Flynn, and HP technical support. However, they aren't responsible for any errors in this page.

We aren't wizards: we are only reporting what we know from our recent experiences. We're posting this information because there seemed to be almost nothing about Omnibooks on the net. Therefore, please treat our information with the skepticism it deserves and don't hold us responsible for any errors. Of course, if you discover any errors or additional information, we'd love to improve our page.

We only know about the Omnibook 600C and 600CT. We got our machines in very early 1996. Earlier, later, or variant models of these machines may, of course, differ in unknown ways. In particular, some earlier models (the 300 and the 530 at least) seem to have non-standard keyboards that do not work under Linux. Fixing this would seem to require getting better information about the hardware from HP.

We originally installed Linux 1.2.13, from the Slackware 3.0 distribution. This required a special procedure because the floppy drive could not be used under Linux. Version 2.0 of Linux includes support for the Omnibook floppy drive and should be used for new installations. We are now running version 2.0.27 (Slackware version, distributed on CD-ROM by Walnut Creek ).


The Omnibook 600C and 600CT are 11.1" by 7.28" by 1.6", and weigh 3.8 pounds, including the battery. They have 75MHz 486DX4 processors and come with 8M of RAM. Ours came with NiMH batteries, although they can also be obtained with Lithium-Ion ones. The keyboard is full-size and has a nice touch. The 600C has a 8.5" dual scan monitor. The 600CT has a 9.5" active matrix monitor. In both cases, the resolution of the monitor is 640 by 480 pixels and the screen can be tilted back almost parallel to the keyboard.

You should not, however, deduce that the two models differ primarily in screen quality. The 600C has an extremely nice dual scan display, so nice that the better quality of the 600CT's screen is only apparent when the two are seen side by side. The important differences between the models lie elsewhere. The 600CT has 16-bit sound system, whereas the 600C only beeps. The 600CT comes with a later version of DOS/Windows, but it has on-line manuals, whereas the 600C comes with proper hardcopy manuals. Finally, the 600C can be upgraded to 16M, but the 600CT can be upgraded to 32M.

The current models have 340M hard disk drives. Linux sees the disk drive as a standard IDE disk drive, but it is physically a standard type III PCMCIA card. Therefore, the size of the hard disk has increased, and presumably will continue to increase, as larger PCMCIA hard disks become available. Machines from discount houses may still have the older (and much less acceptable) 260M hard drives. On the other hand, upgrading or replacing these disks should be extremely easy.

Both models come with the following peripherals:

In addition, HP sells an "enhanced port replicator" for these machines, which provides

For reasons that will become obvious later in this page, we strongly recommend that you buy the port replicator.

What works and what doesn't

The processor and hard drive work under Linux. The on-board monitor, external monitor port (SVGA out), and video card (Chips and Technology 65545) work under XFree86. The serial, parallel, and SCSI-2 ports all work, as does an HP 27247B 10-base-T LAN card installed in the port replicator.

As of version 2.0, the Omnibook's floppy disk drive now works under Linux. The problems with earlier versions (e.g. 1.2.xx) of Linux were due to the fact that the Omnibook can't do DMA to the floppy drive and earlier Linux drivers required DMA. Alain Knaff, the principal maintainer of the Linux floppy driver, implemented a DMA-less driver. (Thanks!)

The Omnibook's floppy drive is noticably slow. This is not a problem in normal use, because one doesn't normally do much I/O to floppies.

Linux APM sofware can communicate with the battery and respond to the Omnibook's on/off switch. Be sure to enable APM when you configure your kernel.

Two things don't work (though perhaps they could be fixed if someone wrote a driver):

The most serious of these problems is that non-functionality of the mice. One can, of course, use a serial mouse. (We are using a Logitech mouse.) However, since there is only one serial port, a serial mouse and a serial modem are mutually exclusive. This problem could be resolved by moving either the mouse or the modem off the serial port: find or build a driver for either the on-board or port-replicator mouse, or build a driver for the PCMCIA port.

We have no idea whether the 600CT's sound system works under Linux, beyond the simple beep which both models happily produce. We have not tried the keyboard port on the port replicator and it's not clear why one would need it given the quality of the on-board keyboard. I've never seen reference to any IR port working under Linux.

Past History

There are several reasons why people may have had problems with the Omnibook in the past. Linux couldn't be installed in the obvious way under earlier versions of Linux , so some people may have given up after trying to install it. Second, we have heard that HP's mobile computing technical support was less helpful in the recent past and has become much better.

Finally, earlier models of the Omnibook were not as nice. Like all notebook computers, they have been improving fast. In particular, their hard disks used to be smaller (e.g. 260M). Also, early models did not come with a floppy drive. A third-party vendor apparently offered a parallel-port floppy drive which could be used on them (at least under DOS). However, this would have made installing Linux (or any other operating system) even more of an adventure.

Our configuration

We are running Linux (and DOS) on an Omnibook 600C with 16M of memory, and a 600CT with 24M of memory. We have an enhanced port-replicator. The port replicator contains an HP 27247B 10-base-T LAN card, providing direct connection into our lab's network. We also have a Supra Fax 288 (28.8K) external modem.

We have an Iomega Zip drive and a Panasonic KXL-D720 PCMCIA CD-ROM player. Both of these can be attached to the port replicator's SCSI-2 port, and work under both DOS and Linux. The extra file space provided by the Zip drive should make it much easier to live with the Omnibook's small hard drive.

It is not easy (at least not in Iowa City) to get the cable required to connect the Zip Drive's DB-25 (25-pin Mac-style SCSI) connector to the Omnibook's HD-50 (miniature 50-pin SCSI-2) connector. We got ours from PC and Mac Connection (1-800-800-1111), who were very fast and very helpful.

We also have a Snappy parallel-port framegrabber, but we have not yet made it work under Linux.

Installing Linux

In general, the Slackware installation procedure works in the obvious way. We used a CD-ROM player connected to the SCSI port on the port replicator. We used the color rootdisk and the bootdisk with support for the aha152x SCSI controller.

Be aware that the floppy drive is very slow, so it will take longer than other machines to read the bootdisk when you boot it. Give it time.

When you boot with the bootdisk, you will need to specify two options:

The aha152x option forces Linux to recognize the Omnibook's SCSI controller. The nodma option tells Linux about the Omnibook's unusual floppy drive.

After you have built a Linux file system (e.g. on partition hda3), you will type something like one of the following option lines:

Be aware that your LAN card will not work until you recompile the kernel. When configuring the kernel options, we found that our LAN card (HP 27247B 10-base-T LAN card) was inside a submenu of "other" network cards.


Booting from the floppy drive is inconvenient, because the floppy drive is external and very slow. We strongly recommend installing lilo. Read the user guide that comes with lilo (/usr/doc/lilo/doc/user.tex). It is long but very clear. It is much more informative than the HOWTOs. Don't run lilo blind: you can trash everything on your disk and have to reinstall from scratch.

We installed lilo in the boot sector of our Linux partition (hda3), not on the main boot sector of the hard disk (hda), to make it easy to revert to the old DOS loader in case of mistakes. Remember to use fdisk (either under DOS or Linux) to make the Linux partition active and make the DOS partition inactive.

Our lilo.conf files are similar to the following:

        append="aha152x=0x340,10,7,1,1 floppy=nodma"

The docked option is used when the Omnibook is attached to its port replicator. The delay specification can probably be left out. We encountered problems when we put in the compact option, which is recommended by some manuals. Our system defaults to booting DOS because this allows us to power down the system using ctrl-alt-del: if you then leave the machine alone, lilo boots DOS, then DOS automatically turns the machine off after a couple minutes.


XFree86 runs just fine on the Omnibook's 640 by 480 on-board monitor, using a serial mouse (on /dev/cua0). The only problem we encountered is that the probeonly option for X would not report any dot clock consistent with our refresh rates, only a dot clock (28.3) that was patently hopeless. Eventually, we just used the clock value (25.2) that we knew to be correct (from speaking to HP technical suport) in our XF86Config, started X, and it worked.

The Omnibook's video card has a Chips and Technology 65545 SVGA chipset. XF86's name for this chipset is "ct65545". The card has 1024k of video RAM. When configuring your Linux kernel, you should select the XF86_SVGA server and (correspondingly) you will specify the screen's driver in your XF86Config as "SVGA" . There seems to be no good way to know what kind of serial mouse you have: select all the vaguely plausible serial mouse drivers when building your kernel.

For 640x480 resolution, the correct vertical refresh rate is 60Hz. The horizontal sync is 31.5KHz. The dot clock (or pixel frequency) is 25.175MHz. There are 8 bits per pixel and this is non-VESA. We obtained this information from HP technical support. We copied the most standard set of horizontal timings (640 664 760 800) and vertical timings (480 491 493 525), corresponding to our refresh and sync values, from the Linux documentation and they worked just fine.

According to HP technical support, the Omnibook can drive an external monitor at higher resolutions. At 800 by 600 resolution, the horizontal sync is 37.9kHz and the dot clock is 40.000MHz (VESA). At 1024 by 768 resolution, the horizontal sync is 48.4kHz and the dot clock is 65.000MHz (VESA). In both cases, the vertical refresh is 60Hz. However, we have not yet received our external monitor, so we have not been able to test the Omnibook's SVGA output and higher X resolutions.

Apparently there are some problems running X at higher resolutions (perhaps not 800 by 600, but only 1024 by 768?) with this chipset. Also, the standard SVGA driver does not use accelerated features of the chipset. The CT65545 and other closely-related CT chipsets are used in several popular laptops, so the problem has attracted the interest of the Linux community. Alpha drivers are being developed: see Nelson Minar's CT65545 page and Ken Raeburn's CT65545 page.

IRQ's and the like

The Omnibook has an ISA bus. As best we understand them, the IRQ assignments are as follows.

The SCSI-2 adaptor has SCSI ID 7.

Other related pages

More information about running Linux on laptops can be found on the Linux Laptop Homepage.

This page was written by Margaret Fleck and Dan Stevenson. It is maintained by Margaret Fleck.