www.openbsd.org/faq/faq12.html
Not only can they be, the system will often perform better when the IRQs are shared, especially on i386 systems. Also, many cards with on-board bridges (such as, multi-port network cards) will not work well in older systems. Most PCI cards use 5v signaling, which is used by most computers. ISA cards are more difficult to configure and have a much greater negative impact on the system's performance. ISA hardware requires much more configuration and understanding than does PCI hardware. In general, you can't just stuff the card in the computer and expect it to magically work. In many machines, if your ISA device is not in a "Plug 'n' Play" (PNP) mode, you must reserve the resources the card uses in the system's BIOS. The 3C509B ships configured in a PNP mode, which unfortunately does not comply with standards, and causes problems in OpenBSD's 34 isapnp support. The adapter is picked up first as a non-PNP device, then again after the PNP support comes on-line, resulting in an extra NIC showing in the dmesg. It is highly recommended that the 3C509B cards have PNP mode disabled and manually configured to non-conflicting settings using the 3Com DOS-based configuration utilities before configuration. The ep driver will pick the cards up at any hardware combination that does not conflict with other devices in the system. If you have multiple 3C509 cards in your system, it is recommended that you label the cards' spine with the MAC address, and use the dmesg to identify which is which. Note that the 3C509, the 3C905 and the 3C590 are often confused. The 3C509 is a 10Mbps ISA card, the 3C905 and 3C590 are PCI cards. NE2000 The original NE2000 NIC was developed in the mid-1980s by Novell. Since then, many manufacturers have produced cards that are very similar, which are generally called NE2000-compatibles, or clones. While some older NE2000-compatible cards performed very well, many of the currently-available ones perform poorly. NE2000-compatibles are supported by the 35 ne driver in OpenBSD. OpenBSD will handle some ISAPNP-capable NE2000-compatible cards well if the ISAPNP mode is turned on. Other cards will have to be set using either jumpers or a DOS-based configuration utility. Unfortunately, as the original NE2000 cards did not have software configuration or ISAPNP support, there are no standards for this -- you need the utility that will have been originally supplied with your specific card. The ne driver supports three configurations of the ISA NE2000 card in the GENERIC OpenBSD kernel: ne0: port 0x240 irq 9 ne1: port 0x300 irq 10 ne2: port 0x280 irq 9 If these settings are not acceptable, you can adjust them using 36 User Kernel Configuration (UKC) or by 37 building a customized kernel. Note that the ne driver is fairly "dumb" -- only the I/O port is probed, if any of the above I/O addresses is detected, the corresponding IRQ is assumed. If this is not the actual IRQ your card is set to, it will not work. Note that there are non-ISA cards that use the ne driver -- PCI and PCMCIA ne cards exist. These notes do not apply to them, these devices are auto-configuring. Most 80386sx systems can't support more than 8M of RAM, which places them in the "For Experts Only" category, as some non-trivial steps and a second computer are required to get going. Also, see the next section: 80386 OpenBSD will run on an 80386 or 80386sx system IF it has a 80387 or 80387sx hardware math coprocessor (Floating Point Unit, or FPU). Unfortunately, these FPUs were not common, so many 80386 systems will not have them. OpenBSD will not run without the FPU on the i386 platform. Again, be aware that this is a very small amount of processor for a crypto-intensive operating system like OpenBSD. You aren't likely to be happy with the performance of such a machine for general use. Fortunately, full 80486DX chips are fairly available, and is an easy upgrade in most systems. This is entirely acceptable, and in fact, even desirable for PCI devices. Some people will say that sharing interrupt requests (IRQs) is bad, however they are either confusing the situation with the ISA bus (where IRQ sharing is not permitted), or past experience with broken hardware or software. If you find ISA devices sharing IRQs, you must correct this problem. OpenBSD/i386 will usually use a USB keyboard and mouse without difficulty after installation. However, installing OpenBSD on a system with a USB keyboard can be difficult, as the install kernels do not have the full complement of USB drivers required for complete USB keyboard support. As machines vary, you may need to experiment: * Some systems have a BIOS option for "Legacy USB support" or something similar. This allows the BIOS to emulate a traditional PS/2 keyboard. If this is not enabled, you will not be able to enter commands at the boot> prompt. However, some systems may run better with this feature turned on, some with it turned off. Some may install better with it in one setting and run better with it in the other. Once you have OpenBSD installed: * Using 40 UKC to disable pckbd0 may result in less "kernel message noise" (usually, pckdc: cmd failed), though if you do this, you will not be able to use a PS/2 mouse. If you have difficulty with your system, you will have to record messages with pencil and paper. Unfortunately, there are a variety of ways in which USB is supported on PCs right now, so you may have to do some experimenting with your system to get the USB keyboard working properly. This is most often seen when using a "switch box" to attach multiple computers to one keyboard, monitor and mouse. You can experiment with different brand and design switch boxes, but OpenBSD seems to be more sensitive to switching the mouse than some other operating systems. If you are not using the mouse, the solution is simple: don't attach the mouse cable to the computer. If you are using the mouse, an easy solution is "one mouse per computer", and switch just the keyboard and monitor. If you just want console access to the machine, you may wish to consider using a 42 serial console instead. Unfortunately, we have a small number of different Mac68k machines in the hands of OpenBSD developers, and thus, only a few are known to work well at this moment. If you can help restore support to currently broken systems, your code would be welcome! OpenBSD uses clock interrupts to keep track of the current time, but these interrupts have the lowest priority in the 43 Mac68k architecture. So, under heavy load, (such as disk or network activity) clock interrupts will be lost and the Unix clock will not advance as it should. Mac OS gets around the time problem by always reading the hardware clock. OpenBSD only reads the hardware clock at boot time and thereafter ignores it. You may notice that, at shutdown, the kernel is not confident enough to write the Unix time back into the hardware clock because this time loss problem is well known. A simple solution is to run rdate on a regular basis, by having a crontab entry for it. This usually shows itself by crashes shortly after the system goes multi-user, and the crash may not be obviously related to the disk system. The solution is to only use one drive on your Mac68k systems. If any partition you are installing to is more than around 500M in size, you can expect the following strange error: Error on SCSIRead(), #5 pos = 0, i = 22, fs = / alloccgblk: can't find blk in cyl The solution to this is to first install a minimal system in a "small" root partition, then boot OpenBSD and relocate things as desired. Create the root partition, create the other partitions you want, newfs them all using the Mac OS utilities. Mount your other partitions on a temporary mount point, and copy over the directories you want to them, as demonstrated 47 here. Following this process, any size can be achieved for the non-root partitions. The 49 bm driver, supporting the BMAC chip used on some MacPPC systems (including early iMacs) has issues when run at 100Mbps. Use CD-ROM, Miniroot, or network boot to do your installation instead.
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