EUG PD
1st April 2000
Categories: Description: Utility
Author: Robert Sprowson
Published in EUG #50
Instructions
This file describes the ROM image RAMFS which drives the RAM board connected via a 24 bit latched address bus to the 1MHz port.
The image requires at least one 16k bank of Sideways RAM, or to be put onto a ROM, to work.
At the prompt, type:| On A Master: | *SRLOAD U.RAMFS 8000 (socket#) *INSERT (socket#) where socket# may be 7, 6, 5 or 4 |
| On A Machine With SWRam: | *LOAD U.RAMFS 8000 |
Then press CTRL-BREAK to initialise.
The image will then be installed into the chosen socket where it will wait until selected as the current filing system. To do this, you can either type *RAM (RETURN), press R-BREAK, issue a sideways ROM service call with FS id 23 or, only on the Master series, by the inclusion of "-RAM-" in the filename.
One page (256 bytes) of memory is claimed as private workspace above OSHWM in the BBC or in the hidden RAM on a Master. This contains pointers, etc, that RAMFS uses. It must not be tampered with.
Note that a hard or power on reset has the effect of 'formatting' the disk and all information will be lost.
Looking at performance, a BASIC program using BGETs/BPUTs/OSGbPb noted the following performance increases over DFS 1.20:
Multiple 411 byte OSGbPb reads ................. x4.05 faster
Multiple 10 byte BGet sequences ................ x1.32 faster
Random setting of PTR then OSGbPb .............. x1.72 faster
Plus of course, there is no overhead for waiting to spin the disk up to speed.
Properties
Filenames can be up to ten letters long with a 1 letter directory name. There can be up to 127 files in the catalogue.
The media title can be up to 16 letters long.
The drive number must always be zero where drive numbers are requested.
File attributes are ignored. Attributes are read/writeable via the OSFile call though there is no *ACCESS command. By default access is set to local RW access.
The filing system id is 23 for RAMFS.
The 'cycle number' does not increment with each write to the RAM disk. Instead it is a 'number of files currently open' status byte, taking the value 0-3. Up to three files may be open at once for any mixture of input, output or random access. The SPOOL/EXEC files are not held open over a filing system change.
Supported OS Calls
OSArgs
| Y=0 A=0 | (Read fs id) |
| Y=0 A=1 | (Read address of *RUN parameters) |
| Y=0 A=255 | (Update all files to media) |
| Y=handle A=0 | (Read sequential pointer) |
| Y=handle A=1 | (Write sequential pointer) |
| Y=handle A=2 | (Read file length) |
| Y=handle A=255 | (Update this file to media) |
OSBGet
Y=handle, byte returned in A is valid only if C=0
OSBPut
Y=handle, A=byte to write
OSFile
| A=0 | (Save a section of memory) If this call fails due to lack of disk space and the filename given already existed, this results in the deletion of that file! |
| A=1 | (Write cat info) |
| A=2 | (Write load address for file) |
| A=3 | (Write exec address for file) |
| A=4 | (Write attributes for file) |
| A=5 | (Read cat info) |
| A=6 | (Delete named file) |
| A=255 | (Load named file,using stored/given address) |
OSGbPb
| A=1,2 | (Put bytes to media) |
| A=3,4 | (Get bytes from media) |
| A=5 | (Read media title and boot option) |
| A=6 | (Read device name and current dir) |
| A=7 | (Read device name and current lib) |
| A=8 | (Read names from current dir) |
OSFind
| A=0 | (Close file, or files) |
| A=&40 | (openin an existing file) |
| A=&80 | (openout a file,deleting the old if it already exists) |
| A=&C0 | (openup an existing file) |
OSFSControl
| A=0 | (Set option) X=0,Y=0 (Reset default OPTions) X=1,Y=0/1 (Turn off/on extended messages) X=4,Y=0/1/2/3 (Set boot option) |
| A=1 | (test for EOF) |
| A=2/3/4 | (Run the given file) |
| A=5 | (Produce catalogue) |
| A=6 | (Shut down filing system) |
| A=7 | (Return handle range) |
| A=8 | (Command about to be executed) |
| A=9 | (Do a *EX) |
| A=10 | (Do a *INFO) |
Additional OS Commands
DIR :drive.directory (Set current directory) LIB :drive.directory (Set current library) TITLE(Set media title) DRIVE (Set drive number) CLOSE (Close all files) DELETE (Delete a single file) RENAME (Rename the given file) EX (Extract info about a dir - only on Master series) INFO (Show info on the given file) WIPE (Delete files, prompting for confirmation for each) DESTROY (Delete files, prompting for confirmation of the batch) ENABLE (Skip warnings before 'dangerous' commands)
Exit Messages
| Escape | the user aborted something waiting for his input |
| Outside file | an attempt was made to move the file pointer past the end of the file |
| Cat full | no free slots could be found in the disk catalogue, despite there probably being space on the disk for the data itself |
| Can't extend | files must be in one contiguous block on the disk, and the file is now too big for its allocated slot |
| Too many open | only 3 files may be open at once |
| Read only | the file involved has only been opened for reading |
| Open | the file involved is already open |
| Exists | an attempt to rename a file to one that exists was made |
| Disc full | there is no free space left |
| Bad option | only OPT0,OPT1,OPT4 are allowed |
| Bad name | the name given contained forbidden characters or was too long |
| Bad drive | a drive number other than zero was used |
| Bad dir | directories must be 1 valid letter long maximum |
| Not found | the requested file was not present on the disk |
| Channel | a call was made with a handle which is either illegal or has already been closed |
Known Problems/Future Enhancements
No *COPY (Unsure of which implementation to do) and therefore no *BACKUP
Tube processor acknowledged but ignored
No *ACCESS command as attributes are ignored at present
No other known problems
History
| v0.65 | Initial release to show it works |
| v0.66 | OSFile A=4 or A=1 allows only the bottom byte of attributes to be written by the user now. (The other 3 bytes are FS dependant and reserved.) |
| v0.72 | If no hardware is found then no attempt will be made to format it on a hard reset (this previously caused the machine to pause for about 10 seconds) and *OPT1,0/*OPT1,1 implemented |
| v0.77 | OSFile A=255 left the <override> address in the user's parameter block instead of the stored load address if *LOAD <filename> <override> was used. Support for LIBs added to the *RUN handler. |
| v0.82 | Added wildcard handler and hence *INFO, *EX, *WIPE, *DESTROY too |
| v0.83 | RAMFS calls that print out information can now be used while *SPOOLing the OSbput routine preserves everything it uses. *WIPE and * DESTROY will no longer allow you to delete open files. Issuing a *CLOSE or *SHUT or swapping between filing systems will will close the SPOOL/EXEC files too. |
| v0.84 | Wildcard matching algorithm altered to search in a different order. Default attributes are set to 3 instead of 7 to ensure the file isn't executed only if moved to ADFS. |
| v0.85 | Reintroduced temporary filing system support for Master series, ensuring the correct FS is left selected at the finish. |
| v0.86 | Fixed bug in BBC B version to ensure workspace was claimed on soft resets. |
Manual (C) 1998 Robert Sprowson
Software (C) 1998 SPROW
