BIOS provides the basic functions needed to boot your machine to allow your operating system to access your hardware. Your system probably provides a BIOS set-up menu, which is used to configure the BIOS. Before installing, you must ensure that your BIOS is setup correctly; not doing so can lead to intermittent crashes or an inability to install Debian. The rest of this section is lifted from the , answering the question, "How do I enter the CMOS configuration menu?". How you access the BIOS (or ``CMOS'') configuration menu depends on who wrote your BIOS software: AMI BIOS Delete key during the POST (power on self test) Award BIOS CtrlAltEsc , or Delete key during the POST DTK BIOS Esc key during the POST IBM PS/2 BIOS CtrlAltInsert after CtrlAltDelete Phoenix BIOS CtrlAltEsc or CtrlAltS or F1 Information on invoking other BIOS routines can be found in . Some &arch-title; machines don't have a CMOS configuration menu in the BIOS. They require a software CMOS setup program. If you don't have the Installation and/or Diagnostics diskette for your machine, you can try using a shareware/freeware program. Try looking in . Many BIOS set-up menus allow you to select the devices that will be used to bootstrap the system. Set this to look for a bootable operating system on A: (the first floppy disk), then optionally the first CD-ROM device (possibly appearing as D: or E:), and then from C: (the first hard disk). This setting enables you to boot from either a floppy disk or a CD-ROM, which are the two most common boot devices used to install Debian. If you have a newer SCSI controller and you have a CD-ROM device attached to it, you are usually able to boot from the CD-ROM. All you have to do is enable booting from a CD-ROM in the SCSI-BIOS of your controller. Other popular option is to boot from a USB storage (also called USB memory stick or USB key). Some BIOSes can boot USB storage directly, and some cannot. You may need to configure your BIOS to boot from a Removable drive or even a USB-ZIP to get it to boot from the USB device. Here are some details about how to set the boot order. Remember to reset the boot order after Linux is installed, so that you restart your machine from the hard drive. As your computer starts, press the keys to enter the BIOS utility. Often, it is the Delete key. However, consult the hardware documentation for the exact keystrokes. Find the boot sequence in the setup utility. Its location depends on your BIOS, but you are looking for a field that lists drives. Common entries on IDE machines are C, A, cdrom or A, C, cdrom. C is the hard drive, and A is the floppy drive. Change the boot sequence setting so that the CD-ROM or the floppy is first. Usually, the Page Up or Page Down keys cycle through the possible choices. Save your changes. Instructions on the screen tell you how to save the changes on your computer. As your computer starts, press the keys to enter the SCSI setup utility. You can start the SCSI setup utility after the memory check and the message about how to start the BIOS utility displays when you start your computer. The keystrokes you need depend on the utility. Often, it is CtrlF2. However, consult your hardware documentation for the exact keystrokes. Find the utility for changing the boot order. Set the utility so that the SCSI ID of the CD drive is first on the list. Save your changes. Instructions on the screen tell you how to save the changes on your computer. Often, you must press F10. Some BIOS systems (such as Award BIOS) allow you to automatically set the CD speed. You should avoid that, and instead set it to, say, the lowest speed. If you get seek failed error messages, this may be your problem. If your system provides both extended and expanded memory, set it so that there is as much extended and as little expanded memory as possible. Linux requires extended memory and cannot use expanded memory. Disable any virus-warning features your BIOS may provide. If you have a virus-protection board or other special hardware, make sure it is disabled or physically removed while running GNU/Linux. These aren't compatible with GNU/Linux; moreover, due to the file system permissions and protected memory of the Linux kernel, viruses are almost unheard of. After installation you can enable Boot Sector protection if you want. This offers no additional security in Linux but if you also run Windows it may prevent a catastrophe. There is no need to tamper with the Master Boot Record (MBR) after the boot manager has been set up. Your motherboard may provide shadow RAM or BIOS caching. You may see settings for ``Video BIOS Shadow'', ``C800-CBFF Shadow'', etc. Disable all shadow RAM. Shadow RAM is used to accelerate access to the ROMs on your motherboard and on some of the controller cards. Linux does not use these ROMs once it has booted because it provides its own faster 32-bit software in place of the 16-bit programs in the ROMs. Disabling the shadow RAM may make some of it available for programs to use as normal memory. Leaving the shadow RAM enabled may interfere with Linux access to hardware devices. If your BIOS offers something like ``15-16 MB Memory Hole'', please disable that. Linux expects to find memory there if you have that much RAM. We have a report of an Intel Endeavor motherboard on which there is an option called ``LFB'' or ``Linear Frame Buffer''. This had two settings: ``Disabled'' and ``1 Megabyte''. Set it to ``1 Megabyte''. When disabled, the installation floppy was not read correctly, and the system eventually crashed. At this writing we don't understand what's going on with this particular device — it just worked with that setting and not without it. If your motherboard provides Advanced Power Management (APM), configure it so that power management is controlled by APM. Disable the doze, standby, suspend, nap, and sleep modes, and disable the hard disk's power-down timer. Linux can take over control of these modes, and can do a better job of power-management than the BIOS. The version of the operating system kernel on the installation floppies does not, however, use APM, because we've had reports of one laptop system crashing when the Linux APM driver is configured. Once you've installed Linux, you can build a custom-configured version of the Linux kernel; see for instructions.