There may be several definitions for a parameter with only one that is active. Which one this is is easy to find if you know that "(\s-2CPU\s+2 == \s-2INTEL\s+2)" is true, and _WORD_SIZE equals 2 in 16-bit mode, and 4 in 32-bit mode.
This is the main configuration file for the MINIX 3. It contains lots of boolean variables to enable or disable drivers and a number of parameters that specify the sizes of system data structures:
NR_PROCS The number of slots in the process table, and thus the maximum number of processes that can be run concurrently. Should be increased from the default 32 if networking is enabled (add 8 for deamons), and if more users are using the system (add 4 for each active session). There are a lot of loops in the kernel scanning the process table, so setting NR_PROCS too high will slow things down a little bit, so don't overdo it.
NR_BUFS The number of disk buffers in the file system server. It is used to keep frequently used disk blocks in memory. 8086 " & " 286 : The default is 40 , and that's about as high as it can be set. 386 : The default is 80 , which is best increased to 1024 if you can spare the memory. More will help, but the effect won't be as pronounced as 1024 is more than enough to contain the working set of one active user.
NR_CTRLRS Number of tasks used for disk or tape controllers. By default 2, maximum 4. You need a controller task for each device class to be handled through a /dev/c n "*" set of devices.
ENABLE_CACHE2 If set to 1 allows the RAM disk to be used as a second level file system cache. Any block that is evicted from the normal cache is both written to disk (if dirty), and copied to the second level cache. If it is needed again then the block is reloaded from the RAM disk if it is still there. 8086 : Forget it, you don't have any memory for it. 286 : Turn it on and set the boot environment variable ramsize to 512 if you have the memory. That's enough to contain the working set of one active user, and is also the maximum FS can handle. 386 : The installation scripts sets ramsize to 1024 if there is enough memory. Your first point of call is to compile a new kernel with ENABLE_CACHE2 off, NR_BUFS set to a large value, and ramsize set back to zero. A normal block cache works much better than a two level arrangement.
ENABLE_AT_WINI Enables the AT or IDE disk driver. (The IDE interface grew out of the old AT disk interface.) Any run of the mill PC needs this driver. You need to assign a driver like this one to a controller task using one of the c n boot variables. See boot (8).
ENABLE_BIOS_WINI Enables the BIOS disk driver. The BIOS driver uses the system BIOS to read or write disk blocks. 8086 : The preferred disk driver for XT class machines. 286 " & " 386 : Use a native driver if possible to avoid switching back to real mode to make BIOS calls. Especially on the 286 this is a painful affair.
ENABLE_ESDI_WINI Enables the ESDI disk driver. Some PS/2 models have this disk.
ENABLE_XT_WINI Enables the XT disk driver. Useful for early IBM/AT machines that have XT disks. In real mode it is best to use the BIOS driver.
ENABLE_AHA1540_SCSI Enables the Adaptec 1540 series SCSI driver.
ENABLE_DOSFILE Enable the "DOS file as disk" driver that is used when MINIX 3 is run from MS-DOS to access a large file as a disk.
ENABLE_FATFILE Enable the "FAT file as disk" driver that interprets a FAT file system to find a large file to use as a disk. This driver combined with a fast native MINIX 3 disk driver is a better choice then the previous driver. (And it works when MINIX 3 is not started from MS-DOS.) This is the last driver that needs to be assigned to a controller task.
ENABLE_SB16 Enable the Soundblaster-16 audio driver.
ENABLE_PRINTER Enable the Printer driver.
DMA_SECTORS The size of the DMA buffer for drivers that use DMA or other drivers that can only do I/O to a single chunk of memory. (BIOS, ESDI, XT, DOSFILE.) Choose a number between 1 and 128 for the sector size of this buffer. The memory cost is twice this amount, because of trouble getting it aligned in memory properly. A value of 16 is the minimum to work well, choose 64 if you have enough memory.
NR_CONSOLES Number of virtual consoles. By default 2 , so you can have two login sessions that can be switched to by ALT-F1, ALT-F2 or ALT-left/rightarrow. If you have an EGA screen then you can specify up to 4 virtual consoles, for VGA you can have 8 . It is best to choose one less to leave some video memory to keep text scrolling fast. You really should read console (4) on this. Note also the console boot variable, you can use it to put more characters on the screen, at the cost of video memory.
NR_PTYS Number of pseudo terminals supported, by default 0 , which disables the driver. Pseudo terminals are used for incoming network logins by telnet or rlogin. One pty is needed per session.
NR_RS_LINES Number of RS-232 lines supported. By default 2 for a normal kernel, but 0 for a tiny kernel used for XT installation. You can save a bit of memory by setting this parameter to zero if you don't need serial lines.
This file contains most of the parameters used by the file system code. Most of these cannot be changed, with the exception of these four:
NR_FILPS Maximum number of open file descriptors for all processes combined. A "File table overflow" error might indicate that this number must be increased.
NR_INODES Maximum number of in-use files for all processes combined. Like above a "File table overflow" error may also indicate that this number should be increased. In cases like these one usually doubles both parameters. (If one table runs out then the other one is likely to run out also anyway.)
NR_SUPERS Number of file systems that can be mounted. Again a "file table overflow" error is given if this table is full, but it will be produced by the mount command, so you know what's wrong in this case.
NR_LOCKS Number of active file locks by fcntl (2). These locks are often used by programs that update a shared file, like mail programs do with mail boxes. A "no locks available" error indicates that this table has run out.