Over the years, i386 systems have been expanded time and time again to surpass their own limits. They’re based upon an architecture that could originally handle a maximum of 640KB of RAM, after all! The OpenBSD kernel — indeed, all modern operating system kernels — work around these limits in a manner mostly transparent to the user, but when the system is first booting you’re trapped with the BIOS limitations.

Many old i386 systems have a 504MB limit on hard drives, on which the BIOS cannot get at anything beyond the first 504MB of data on a disk. If your BIOS cannot find your operating system kernel in that first 504MB, it cannot boot the system. Check your hardware manual; if it makes any references to a 504MB limit, this affects you. You absolutely must place your entire root partition within the first 504MB of disk.

Additionally, for some time i386 systems had a similar (not identical) 8GB limit. OpenBSD still obeys that 8GB limit. Even if your system is not susceptible to the 504MB limit, your entire root partition must be completely contained within the first 8GB of disk.

Of course, if you follow my advice and make your root partition 500MB you will never have to worry about either of these restrictions and the potential damage that they can inflict.

If you break these rules, your system will probably appear to work. The second you upgrade your system, or move the file /bsd, the computer will quite probably refuse to boot. Save yourself much pain; make the root partition 500MB, and the first partition on the disk, and this problem will never affect you.

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