MINI-UNIX - Revision history

Larsbrinkhoff: /* External links */ Installing Mini-UNIX on SIMH.

2025-02-03T05:37:13Z

‎External links: Installing Mini-UNIX on SIMH.

Jnc: /* User-visible compatibility */ Exact size limit

2023-06-21T19:16:02Z

‎User-visible compatibility: Exact size limit

Jnc: /* External links */ Correct location for OS source

2023-05-19T15:41:08Z

‎External links: Correct location for OS source

Jnc: /* External links */ bah, typo

2023-05-19T15:33:49Z

‎External links: bah, typo

Jnc: Location of 'user' area

2023-05-19T14:49:58Z

Location of 'user' area

Jnc: /* External links */ +BSTJ memo on MX

2022-09-29T19:37:41Z

‎External links: +BSTJ memo on MX

Jnc: +link

2022-06-01T07:57:26Z

+link

Jnc: /* Internal changes */ typo

2022-06-01T04:41:37Z

‎Internal changes: typo

Jnc: /* External links */ +useful individual docs

2022-01-09T23:11:48Z

‎External links: +useful individual docs

Jnc: same FS asV6 allows cross-mounting; finish re-org

2022-01-09T14:11:19Z

same FS asV6 allows cross-mounting; finish re-org

@@ Line 74: / Line 74: @@
 ** [http://ana-3.lcs.mit.edu/~jnc/tech/unix/Mini/20Regenerating_System_Software.pdf Regenerating System Software]
 ** [http://ana-3.lcs.mit.edu/~jnc/tech/unix/Mini/01Setting_Up_Mini-UNIX.pdf Setting Up Mini-UNIX] - lightly edited version of the V6 one
 * [https://www.tuhs.org/cgi-bin/utree.pl?file=Mini-Unix/usr/doc/new/ MINI-UNIX documents source]
 * [http://ana-3.lcs.mit.edu/~jnc/tech/unix/Mini/Mini.html Running MINI-UNIX on the LSI-11]

@@ Line 26: / Line 26: @@
 The removal of ptrace() means there is no interactive [[debug]]ging; this is not a major hardship, as the lack of memory management means that a buggy user program can crash the system anyway.
-MINI-UNIX uses the same [[file system]] as V6; this allows MINI-UNIX packs to be 'mounted' on V6 systems (either real, or simulated), which is very convenient for working on them. The maximum file size supported is 1MB; 'large' files are supported, but not 'huge' files (those with two levels of indirect blocks).
+MINI-UNIX uses the same [[file system]] as V6; this allows MINI-UNIX packs to be 'mounted' on V6 systems (either real, or simulated), which is very convenient for working on them. The maximum file size supported is 1MB (512*256*8 = 1,048,576 bytes); 'large' files are supported, but not 'huge' files (those with two levels of indirect blocks).
 ===Modified commands===

@@ Line 67: / Line 67: @@
 * [https://www.tuhs.org/Archive/Documentation/TechReports/Heinz_Tech_Memos/TM-77-1352-1_The_MINI-UNIX_19770103.pdf The MINI-UNIX System] (TM 77-1352-1)
 * [https://www.tuhs.org/cgi-bin/utree.pl?file=Mini-Unix Mini-Unix] - file tree at [[The Unix Heritage Society|TUHS]]
-** [https://www.tuhs.org/cgi-bin/utree.pl?file=Mini-Unix/usr/source source] - for for all commands
+** [https://www.tuhs.org/cgi-bin/utree.pl?file=Mini-Unix/usr/source source] - for most commands
-** [https://www.tuhs.org/cgi-bin/utree.pl?file=Mini-Unix/usr/sys sys] - OS source
+** [https://www.tuhs.org/cgi-bin/utree.pl?file=Mini-Unix/usr/sys/source source] - a few other MINI-UNIX-specific things
 * [http://www.tavi.co.uk/unixhistory/mini-unix/munix-documents.zip MINI-UNIX documents]
 ** [http://www.tavi.co.uk/unixhistory/mini-unix/Mini-UNIX_Memo.txt The MINI-UNIX System]

@@ Line 66: / Line 66: @@
 * [https://www.tuhs.org/Archive/Documentation/TechReports/Heinz_Tech_Memos/TM-77-1352-1_The_MINI-UNIX_19770103.pdf The MINI-UNIX System] (TM 77-1352-1)
-* [https://www.tuhs.org/cgi-bin/utree.pl?file=Mini-Unix Mini-Unix] - file tree at [[he Unix Heritage Society|TUHS]]
+* [https://www.tuhs.org/cgi-bin/utree.pl?file=Mini-Unix Mini-Unix] - file tree at [[The Unix Heritage Society|TUHS]]
 ** [https://www.tuhs.org/cgi-bin/utree.pl?file=Mini-Unix/usr/source source] - for for all commands
 ** [https://www.tuhs.org/cgi-bin/utree.pl?file=Mini-Unix/usr/sys sys] - OS source

@@ Line 42: / Line 42: @@
 Because of the way user commands are run in high memory in a single address space, user commands are [[relocatable binary|linked]] to run at a high [[address]] (usually 060000, instead of at 0 as on standard V6.
-Thus, 24KB (notionally) is normally allocated to hold the kernel (with a modest number of processes and [[disk]] [[buffer]]s), leaving 32KB available for user commands/applications. (The "notionally" is because that 24KB also includes the 'user' structure: a per-process swappable data area, 1KB in size (it includes the process' kernel [[stack]]); thus 23KB is actually available for the kernel.)
+Thus, 24KB (notionally) is normally allocated to hold the kernel (with a modest number of processes and [[disk]] [[buffer]]s), leaving 32KB available for user commands/applications. (The "notionally" is because that 24KB also includes the 'user' structure: a per-process swappable data area, stored at 056000 - i.e. contiguous with the process, for swapping; 1KB in size (it includes the process' kernel [[stack]]). Thus 23KB is actually available for the kernel.)
 This division can be altered, albeit painfully (all the command binaries have to be re-linked to the new boundary address), to allow the size of the kernel to vary.
@@ Line 66: / Line 66: @@
 * [https://www.tuhs.org/Archive/Documentation/TechReports/Heinz_Tech_Memos/TM-77-1352-1_The_MINI-UNIX_19770103.pdf The MINI-UNIX System] (TM 77-1352-1)
 * [http://www.tavi.co.uk/unixhistory/mini-unix/munix-documents.zip MINI-UNIX documents]
 ** [http://www.tavi.co.uk/unixhistory/mini-unix/Mini-UNIX_Memo.txt The MINI-UNIX System]

@@ Line 1: / Line 1: @@
-'''MINI-UNIX''' is a somewhat limited variant of [[UNIX Sixth Edition|V6 Unix]] written by Heinz Lycklama, for use on models of the [[PDP-11]] such as the [[PDP-11/05]] which did not have [[memory management]] (which was required for early Unix versions from 4 onward). Although it is not full Unix, it retains a large amount of the functionality of the original.
+'''MINI-UNIX''' is a somewhat limited variant of [[UNIX Sixth Edition|V6 Unix]] written by Heinz Lycklama, for use on models of the [[PDP-11]] such as the [[PDP-11/05]] which did not have [[memory management]] (which was required for early Unix versions from [[UNIX Fourth Edition]] onward). Although it is not full Unix, it retains a large amount of the functionality of the original.
 Most V6 [[application]]s run without [[source code|source]] modification on MINI-UNIX, although it is not [[object code|binary]]-compatible with V6. This is a result of the lack of memory management in the machines which run MINI-UNIX; the [[kernel]], and [[user]] commands (as [[process]]es), share a single PDP-11 [[address space]], with the kernel in low memory, and the processes (one at a time) in high memory.
@@ Line 5: / Line 5: @@
 There was a second, earlier, stripped-down variant of V6 for PDP-11's without memory management, [[LSX]]; it differed from MINI-UNIX in being targeted at machines with more limited amounts of [[main memory]] (a real concern with early machines, which often came with limited amounts). MINI-UNIX was targeted at machines with the full 56KB possible on such PDP-11's.
-MINI-UNIX did not originally support the [[LSI-11]], but there are no significant architectural differences between the LSI-11 and other 'small' PDP-11's, so  MINI-UNIX was historically brought up on the LSI-11. (The main significant difference is that in the LSI-11, access to the [[Processor Status Word|PS]] requires use of special [[instruction]]s; see [[Running UNIX V6 on an -11/23|here]] for other issues.)
+MINI-UNIX did not originally support the [[LSI-11]], but there are no significant architectural differences between the LSI-11 and other 'small' PDP-11's, so MINI-UNIX was historically brought up on the LSI-11. (The main significant difference is that in the LSI-11, access to the [[Processor Status Word|PS]] requires use of special [[instruction]]s; see [[Running UNIX V6 on an -11/23|here]] for other issues.)
 That version has since apparently been lost; however, because of the wide availability of the LSI-11 in the vintage computer community, MINI-UNIX has recently been ported to the LSI-11 again, to provide a Unix experience on those machines. (See link below.)
@@ Line 18: / Line 18: @@
 * prof()
-[[Pipe]]s are not supported, not only because of space in the [[operating system|OS]], but because a process swap-out and -in will be required every time a different stage needs to run, leading to poor performance.
+[[Pipe]]s are not supported, not only because of space in the [[operating system|OS]], but because a process [[swapping|swap]]-out and -in will be required every time a different stage needs to run, leading to poor performance.
 Although pipes are not supported, the [[command processor|shell]] supports the pipe command syntax ('|'), by use of temporary files (modulo the amount of free space on the disk, of course).
@@ Line 42: / Line 42: @@
 Because of the way user commands are run in high memory in a single address space, user commands are [[relocatable binary|linked]] to run at a high [[address]] (usually 060000, instead of at 0 as on standard V6.
-Thus, 24KB (notionally) is normally allocated to hold the kernel (with a modest number of processes and [[disk]] [[buffer]]s), leaving 32KB available for user commands/applications. (The "notionally" is because that 24KB also includes the 'user' structure: a per-process [[swapping|swappable]] data area, 1KB in size (it includes the process' kernel [[stack]]); thus 23KB is actually available for the kernel.)
+Thus, 24KB (notionally) is normally allocated to hold the kernel (with a modest number of processes and [[disk]] [[buffer]]s), leaving 32KB available for user commands/applications. (The "notionally" is because that 24KB also includes the 'user' structure: a per-process swappable data area, 1KB in size (it includes the process' kernel [[stack]]); thus 23KB is actually available for the kernel.)
 This division can be altered, albeit painfully (all the command binaries have to be re-linked to the new boundary address), to allow the size of the kernel to vary.

@@ Line 52: / Line 52: @@
 Based as it is on V6, given the close match in the system-call interface, one might think that the internals are a close match to V6. That is not quite true: there are some significant differences. A thorough comparison has not been performed, but here are some significant differences that have been found.
-The interface from the I/O system to [[device driver]]s is mostly the same, so that existing V6 device drivers can generally be basically be 'dropped in', almost un-modified. In particular, the interface to 'character (un-structured) devices is identical, as is that to the 'tty' driver; the interface to the block device buffer system (for [[mass storage]] devices) is also identical. The two minor aspects that are changed are:
+The interface from the I/O system to [[device driver]]s is mostly the same, so that existing V6 device drivers can generally be basically be 'dropped in', almost un-modified. In particular, the interface to 'character' (un-structured) devices is identical, as is that to the 'tty' driver; the interface to the block device buffer system (for [[mass storage]] devices) is also identical. The two minor aspects that are changed are:
 * since the system is limited to less than 64KB of memory, the 'extended memory' field in block device buffer header is not present;

@@ Line 65: / Line 65: @@
 ==External links==
 * [http://www.tavi.co.uk/unixhistory/mini-unix/munix-documents.zip MINI-UNIX documents]
 * [https://www.tuhs.org/cgi-bin/utree.pl?file=Mini-Unix/usr/doc/new/ MINI-UNIX documents source]
 {{Nav Unix}}