🚀 go-pugleaf

Archive-name: acorn/faq

   Comp.Sys.Acorn FAQ List. Last alterations 11/Dec/1993
   -----------------------------------------------------

-------------------------------------------------------------------------------
Recent alterations :-
       Q8 amended slightly.
       Q13 ammended for the A30x0 series.
       Q16 spelling and slight semantics correction.
-------------------------------------------------------------------------------

   Contained below is a list of the most commonly asked questions about
Acorn machines in comp.sys.acorn. Before posting to comp.sys.acorn, if you
are new to the group, check to see if your question(s) are already answered
below. Corrections and/or additions to the list can be emailed to :-

banks_p@kosmos.wcc.govt.nz

And I'll try to add them as soon as possible....

    When reading this FAQ List it is reccomended that you use a text editor
if you are not interested in reading every question's answer. Each answer is
seperated by a line of '-' characters. To find the answer you are interested
in try searching for (in !Edit) "--\x0AQ##)" using Magic characters where ##
is the question number you are interested in the answer to. This will leap
directly to the answer.

    The posted sections of the FAQ is available from an email server at MIT.
To request the FAQ from this server send an email to mail-server@rtfm.mit.edu.
No subject is needed and the body should be :-

send /pub/usenet/news.answers/acorn/faq

Also stored there is Gerben Vos's Acorn Archive list. This can be obtained
in a similar manner to the faq with the email body being :-

send /pub/usenet/news.answers/acorn/archives

   Finally sections of this FAQ are stored in another email server to reduce
bandwidth when posting it due to these sections being commonly asked but not
quite often enough to warrant the continual posting. To obtain these
sections from the email server send mail to the address
'banks_p@kosmos.wcc.govt.nz' with the subject (case and spelling important
ignore the quotes.) "ServerMail". The body of the message should be of the
form :-

Start:
[line-limit: <x lines per message>]
Section: FAQData
Send: <filename>
End:

All commands in the body of the message are case insensitive. The line-limit
command is completely optional and multiple send commands are possible if
you to request more than one file at a time.

   Please remember that this server is a) in Beta test. I only coded it
recently and there may be some lurking bugs in it yet. & b) at the other end
of a 2400 baud modem. Thus frivoulous requests for large files will not be
appreciated. Also if you get the Subject lines case or spelling wrong that
email will be sent to me instead of the server. Not unsurprisingly I
probably won't be terribly appreciative to receive email server requests in
my personal email section...

Index of Questions
------------------

Q1) I have obtained [PD] program X but find it needs [version Y.YY of]
      module Z, which I don't have. Where can I get it?

Q2) What version of module X can I assume that all users have?

Q3) What's the minimum version of module X that my program needs? What
      features were introduced/what bugs were fixed in which versions?

Q4) I have had problems with my printer. It's a dot matrix printer, when
      printing graphics or a document, it sometimes mangles a line of
      output, usually printing a $ sign, too.

Q5) Why have there been no postings to comp.{binaries,sources}.acorn
       recently?

Q6) What archives/FTP sites are available?

Q7) How can I protect against viruses?

Q8) Where can I obtain !Killer?

Q9) What is a VIDC enhancer? Will I need one for my new multisync monitor?

Q10) What are the main new features of RISC OS 3?

Q11) How do I enable solid drags in Risc OS 3?

Q12) What kind of Acorn machines are there?

Q13) What are the memory limits of the Acorn machines?

Q14) What is a second processor and what second processors are there?

Q15) Are there any cards for IBM PC or compatable machines that Acorn have
      produced?

Q16) What configuration of serial cable should I use on my Arc for modem
work?

Q17) Can PC VGA Monitors be added to an Archimedes?

Q18) What is ADFSBuffers and what is the best setting for it?

Q19) What is the current File-type allocation ranges and why won't Acorn
      provide a full file-type list?

Q20) My disc gives me a 'Broken Directory' or my Free Space Map is corrupt,
      what can I do?

Q21) My hard drive gives me disc errors when I use, what do the error
      numbers mean?

Q22) What does the power on self-test check and how does it signal errors
      back to you?

Q23) Is there a Modula 2 compiler for the Arc?

Q24) Is Virtual Memory possible under RiscOS?

Q25) How compatible with other systems is an Archimedes?

----------------------------------------------------------------------------
Q1) I have obtained [PD] program X but find it needs [version Y.YY of]
module Z, which I don't have. Where can I get it?

   All patch modules and current versions of Clib and its ilk are sited on
the NZ info-server and can be obtained from there if you are sited in NZ.
Ideally your dealer will also have copies of them too and you should be able to
obtain them from them. (If they don't you may like to pass on the ones from the
info-server if you request them, so that they are up to-date.)

----------------------------------------------------------------------------
Q2) What version of module X can I assume that all users have?

   Currently the version numbers are :-
   Clib        v3.75
   Colours     v0.52
   FPEmulator  v2.80
   IRQUtils    v0.12
   Hourglass   v2.02
   Sound       v1.13
   WimpUtils   v0.04

   All of these modules are only needed if you intend running your applications
on Risc OS 2 machines. The functionality of all these module versions have been
incorporated into ROM under Risc OS 3.

----------------------------------------------------------------------------
Q3) What's the minimum version of module X that my program needs? What
features were introduced/what bugs were fixed in which versions?

   These details will come with the release notes accompanying the module and
the particular program, if properly done, will inform you of which versions of
the module you need as required.

----------------------------------------------------------------------------
Q4) I have had problems with my printer. It's a dot matrix printer, when
printing graphics or a document, it sometimes mangles a line of output,
usually printing a $ sign, too.

Get your dealer to carry out Field Change Order XXX (which corrects the
problem). Or if you are competant enough do it yourself like this :-

1)  Remove the circuit board from the computer.

2)  Locate and identify resistor R24. Cut the leg of R24 closest to IC9, and
carefully move the free end of R24 away from the adjacent resistor. Secure R24
to the PCB with adhesive (for example Loctite TAC PAC), leaving the free end of
R24 available for soldering.

3)  Prepare new IC (74HC14) by:
          Removing pins 5,6,8,9,10,11,12 and 13
          Lift pins 1 and 4 ready to solder leads
          Lift pins 2 and 3, and solder them together

4)  Position new IC onto IC15 piggyback fashion so that pin 1 of the new IC is
directly above pin 1 of IC15. Solder pins 7 and 14 of the new IC to pins 7 and
14 of IC15.

5)  Solder thin insulated lead from pin 1 of the new IC to the free end of R24.
Solder a second insulated lead from pin 4 of the new IC to the vacated pad of
R24. Keep these leads as short as possible, and secure them to the PCB with
adhesive.

6)  Reassemble the computer and check operation of the printer port.

The 74HC14 IC is widely available.........(Acorns part No)....

Please note that it is particularly important that a profile of this
modification is kept as low as possible, to ensure that there is no fouling of
the modification on any podules that may be fitted to the computer.

Be warned that modifying your Archimedes invalidates the warranty on it and
should preferrably be carried out by an Acorn sanctioned technician.
----------------------------------------------------------------------------
Q5) Why have there been no postings to comp.{binaries,sources}.acorn
recently?

The moderators run c.b.a and c.s.a in their spare time. They may not
have any at the moment - they're studying hard at University. Please be
aware the submissions address for the binaries and sources groups is
cba@acorn.co.nz and *not* the moderators 'home' addresses - the distinction
is important as they have to pay for incoming email at these addresses.

----------------------------------------------------------------------------
Q6) What archives/FTP sites are available?

See the regular (fortnightly) posting by Gerben Vos.

----------------------------------------------------------------------------
Q7) How can I protect against viruses?

Pineapple Software have produced a program called !Killer, which is the
definitive means of checking for or killing viruses. See the next question.

There are also a few PD programs around, but these tend to detect only
a small subset of the viruses in circulation. !VKiller used to be OK,
but it is no longer maintained, is now seriously out of date and fails to
work under Risc OS 3. Out of the PD virus utilities the current best is Tor
Houghton's Scanner. This detects most known virues and removes quite a few
as well and serves as a good secondary defense if Killer is unavailable to
you. Scanner should be available on various FTP/Email servers.

----------------------------------------------------------------------------
Q8) Where can I obtain !Killer?

It is now a commercial product and will be distributed by Pineapple
Software. Who can be reached at:-

  39 Brownlea Gardens, Seven Kings, Ilford, ESSEX IG3 9NL
  Tel. +44 (81) 599 1476  Fax +44 (81) 598 2343
  via email :-
  sales@pinesoft.demon.co.uk
  support@pinesoft.demon.co.uk

Early versions (up to 1.26) are PD, but should not be used now as they are
ineffective against the new crop of virus that have subsequently appeared
since it's release.

----------------------------------------------------------------------------
Q9) What is a VIDC enhancer? Will I need one for my new multisync monitor?

   A VIDC enhancer is basically a clock change for your VIDC. Most Arcs (bar
the A540 and newer machines) have 24 MHz VIDC chips installed in them. A VIDC
enhancer increases this to 36 MHz allowing much higher resolution screen
modes to be displayed on your Arc. (800x600x16 or SVGA standard becomes
available.) You do *not* need one to use a Multisync monitor - the standard
VIDC handles that just fine. However having a VIDC enhancer is only really
useful if you do have a Multi-sync monitor.

----------------------------------------------------------------------------
Q10) What are the main new features of RISC OS 3?

   This information is now contained in my email server. If you wish to know
the 'new' features of RO3 over RO2 then send a request to my email server, as
detailed at the start of the FAQ, for the filename 'RO3diffs'.

----------------------------------------------------------------------------
Q11) How do I enable solid drags in Risc OS 3?

   Solid drags are controlled by bit 1 in byte 28 of the CMOS RAM. Setting
this bit enables solid drags on all solid drag 'aware' applications. However
setting this bit using a *FX command from the command line is a foolish way
to do it, as this will unset/set the other 7 bits in that byte which have
meaning to FileSwitch and the Wimp. Accordingly the reccomended way to set
this bit is using a program like this basic one enclosed below :-

   REM Toggle state of DragASprite bit in CMOS

   REM Read byte
   SYS "OS_Byte",161,&1C TO ,,byte%
   REM EOR byte with mask for bit 1
   byte% = byte% EOR 1<<1
   REM Write byte back again
   SYS "OS_Byte",162,&1C,byte%
   END

Which safely sets bit 1 while preserving the settings of the other bits.

(thanks go to Micheal J Hardy for this one.)
----------------------------------------------------------------------------
Q12) What kind of Acorn machines are there, and what are their
   specifications?

   The full list of Acorn made machines is somewhat lengthy now and are
mostly no longer in manufacture. Accordingly this list distributed in the
FAQ includes only Archimedes/ARM based machines, which are the currently
manufactured by Acorn. A full list is maintained in my email server under
the filename 'MachineLst'. This is, as far as I am aware, a complete list
of all Acorn machines made with the possible exception of the latest
machines for which I have yet to get the detailed specifications.

A5000 - the A5000 is the first machine to feature high density (quad - 1.6 Meg
   formated) drives by default as well as the latest (at the time) version of
   Risc OS - version 3. It also features an inbuilt IDE hard drive (40 Meg) on
   it's higher end model. With the re-release of the series the basic hard
   drive size has been upgraded to 80 Meg.
   Released late 1991.
   1024k Memory
   Advanced Disc Filing System by default with High Density drives.
   IDE interface by default.
   ARM 3 processor. (25 MHz)
   12 MHz RAM.
   2048k OS in ROM.
   ~13.5 MIPS.

A4 - Acorns first portable machine. The A4 is functionally an A5000 in portable
   form. Featuring power save modes, an LCD screen and software configuration
   of the power saving features it was released July 1992. It is called the A4
   because it's footprint on a desk is apparently that of an A4 piece of paper.
   It is interesting to note that the A4 is *not* an A5000 squeezed into
   portable form but rather the A5000 is the A4 in desktop form, whereby the
   A5000 design was largely a spin off from the design of the A4.
   2048k Memory
   Advanced Disc Filing System by default with High Density drives.
   ARM 3 processor. (24 MHz normally, 6 MHz in power save mode.)
   12 MHz RAM. (3 MHz in power save mode.)
   2048k OS in ROM.
   ~13.25 MIPS.

A30x0 - Two models of this machine exist the A3010 and the A3020. Both are
   designed as low end 'family solution' machines. They are also among the first
   machines to feature the ARM250 processor offering improved performance over
   an ARM2 (but less than an ARM3) and are designed to supplement the A3000
   machine as a low cost entry machine into the Acorn world. Its other main
   claim to fame is it is the first Archimedes series machine that features
   joystick ports (only in 3010 model, the 3020 has a network connector
   instead.). Launched August 27th 1992.
   1024k Memory
   Advanced Disc Filing System by default with High Density drives.
   IDE 60 Mb Hard Drive (only in A3020 with HD option).
   ARM 250 processor
   12 MHz RAM.
   2048k OS in ROM.
   ~7.2 MIPS

A4000 - This is a higher end more expandable version of the A30x0 series
   machines and is in a three box format similar to the A5000. It also is
   driven by an ARM 250 processor however it features over the A30x0 machines
   optional Ethernet & Econet ports, a high density floppy drive and an 80Mb
   IDE drive by default. The aim of this machine is strongly towards the home
   office and more 'serious' applications than the A300x0 series. Launched
   August 27th 1992.
   2048k Memory
   Advanced Disc Filing System by default with High Density drives.
   IDE 80 Mb Hard Drive by default.
   ARM 250 processor
   12 MHz RAM.
   2048k OS in ROM.
   ~7.2 MIPS

A5000 (alpha variant) - This is an improved variant on the A5000 featuring a
   considerably faster processor, 33 MHz, with the ability to have a similarly
   clocked FPA unit installed. It also features a considerably larger base hard
   drive size of 160 Mb on the 4 Mb model, the lower 2 Mb model still as an 80
   Mb drive. Finally it has improved alterations to it allowing easy expansion
   of the machine to 8 Mb of memory by default. (IE without having to use third
   party solutions.) Released 10th September 1993.
   2048k Memory
   Advanced Disc Filing System by default with High Density drives.
   IDE interface by default.
   ARM 3 processor. (33 MHz)
   12 MHz RAM.
   2048k OS in ROM.
   ~16.96 MIPS.
----------------------------------------------------------------------------
Q13) What are the memory limits of the Acorn machines?

   For the most part the 8 bit machines were limited to a maximum of around
   256k of memory. Although various expansion systems including second
   processors effectively meant the upper limit was about 1 Meg.
   For the 32 bit machines *the* upper limit currently is 16 Meg of memory.
   Not all of the range of machines are capable of this however and the list
   looks something like this :-

   A3xx - 8 Megs maximum through third party, 1 Meg official limit.
   A4xx  & A4xx/I - 8 Megs maximum through third party, 4 Megs official
          limit.
   A3000 - 4 Megs maximum through third party, 2 Megs official limit.
   A540  - 16 Megs maximum.
   A5000 - 8 Megs maximum through third party, 4 Megs official limit.
   A4 - 4 Megs official limit.
   A30x0 - 4 Megs official limit.
   A4000 - 4 Megs official limit.
   A5000 (alpha variant) - 8 Megs official limit.

----------------------------------------------------------------------------
Q14) What is a second processor and what second processors are there?

   A second processor was the generic name for a range of parasite
   processors that could be linked to Acorn's 8 bit machines via what was
   called the `Tube` interface. Basically the host machine became dedicated
   to handling the Input and Output while the second processor would do the
   higher level functions (like running your programs). The second processor
   ran asyncronously to the host processor allowing incredible increases in
   execution speed for programs. A wide range of processors were supported
   this way allowing Acorn's eight bit range of machines to remain viable
   and useful for much longer than their technology would suggest.

   The Second Processors that existed are :-

Z80 second processor.
6 MHz RAM.
64k Memory.
CP/M OS.
External second processor for all eight bit machines.

6502 second processor.
3 MHz RAM.
64k Memory.
Extended version of the BBC MOS.
External processor for all eight bit machines.

32016 second processor.
Unknown.
256k-4096k Memory.
Unknown. (Panos at a guess)
External processor for all eight bit machines.

ARM 2 second processor.
8 MHz RAM. (Guess...)
4096k Memory.
Brazil OS.
External processor for all eight bit machines.

6502 co-processor. (internal second processor).
4 MHz RAM.
64k Memory.
Extended version of BBC MOS.
Internal processor for Master 128 machines but could be fitted external to
   the other eight bit machines.

80186 co-processor.
10 MHz RAM.
512k Memory.
DR-DOS+ with GEM.
Internal processor for Master 128 machines but could be fitted external to
   the other eight bit machines.

----------------------------------------------------------------------------
Q15) Are there any cards for IBM PC or compatable machines that Acorn have
produced?

   Yes. Three cards in total :-

Springboard.
  ARM 2 processor.
  4096k Memory.
  8 MHz RAM.
  Brazil OS.

PC ARM development system.
  Precursor to Springboard. Hardware functionally identical.

Ecolink.
  An econet link card for the PC.

----------------------------------------------------------------------------
Q16) What configuration of serial cable should I use on my Arc for modem
work?

   Here follows a diagram of the necessary connections for common terminal
programs to work properly. They are as far as I know the informal standard
agreed upon by commercial comms software developers for the Arc.

   Pins 1, 4, and 8 must be connected together inside the 9 pin plug. This
is to avoid the well known serial port chip bugs. The modem's DCD (Data
Carrier Detect) signal has been rerouted to the Arc's RI (Ring Indicator)
most modems broadcast a software RING signal anyway, and even then it's not
really necessary to detect it for the modem to answer the call.

 Arc (9 pin)                      Modem (25 pin)
 -----------                      --------------

 +---1---DCD
 |
 |   2---RxD------------------------RxD----3
 |
 |   3---TxD------------------------TxD----2
 |
 +---4---DTR------------------------DTR---20
 |
 |   5---0v-------------------------SG-----7
 |
 |   6---DSR------------------------CTS----5
 |
 |   7---RTS------------------------RTS----4
 |
 +---8---CTS

     9---RI-------------------------DCD----8

   Of course you can connect the Modem pin 20 to any one of pins 1, 4, or 8
on the Archimedes plug, as they are all connected together anyway.

   Chocks Away Extra Missions (the flight simulator from 4th Dimension)
suggests that the serial cable be wired as above except that pins 1-4-6 are
connected together and the modem's CTS (pin 5) be connected to the Arc's pin
8 (ie the connections at pins 6 and 8 be swapped over at the Arc's end).
This has been and it also seems to work fine.

   However newer Arc's like the A5000 have come out (and indeed the
occasional A310) with a `corrected` serial port. This newer serial port
operates as it should and is directly compatible with standard PC cables.
Most comms software about at the moment does not take this in account and
assumes that you have a cable patched in the manner described above. If you
do not use such a patched cable on these `fixed` serial ports the software
will generally fail to work.

----------------------------------------------------------------------------
Q17) Can PC VGA Monitors be added to an Archimedes?

   It depends on what monitor you have, and what Archimedes you have. There
are two main types of PC VGA monitors out there...

   1) Fixed Frequency
      These monitors will only display video signals with certain
      line and refresh rates. They will typically only display
      CGA / EGA / VGA modes.

   2) Multi Frequency
      These monitors will display any video signal within a certain
      range, typically 30-50Khz line rate and 50-80Hz refresh rate.

   Type 1 almost always require seperate syncs as the monitor uses the
polarity of the syncs (mainly positive going negative or mainly negative
going positive) to determine what the line and refresh rate should be.

   Type 2 vary. Some require seperate syncs (vertical and horizontal) and
others will work with composite syncs (vertical and horizontal EOR
together).

   As PC monitors typically start at a line rate of 30Khz compared to the TV
broadcast modes (mode 12 etc.) that have a line rate of 15Khz, VIDC has to
do more work to obtain a 30Khz line rate. This means that you computer will
slow down silghtly if you use a 30Khz+ line rate monitor. If you have an ARM
3 fitted such slow downs will probably be negligable.

   Now, depending on what type of Archimedes you have depends on what type
of monitor you can use.

   A540 / A5000 / A4 / A3010 / A3020 /A4000
      Has software control over the polarity of the syncs and what
      frequency VIDC is clocked at.

      The A540 with RiscOS 2 can only use modes 26-28 (640x480)
      [I can't rember if an A540 has a mode 31, help?]. However, by
      changing links and a *configure option, you can get the computer
      to generate seperate syncs with no problem.

      The other machines  with RiscOS 3 can do even better. If you tell the
      computer that you have a VGA monitor it will re-map all of the
      15Khz line rate modes up to 30KHz line rate. This means that
      you can play your games that require mode 12 / 13.
      However, as a PC monitor is designed to display 320 lines 
      minimum then you will get a 'letterbox' effect as mode 12 has
      only 256 lines.

      All these machines have 24Mhz, 25.175Mhz and 36Mhz crystals to drive
      VIDC with. The 25.175Mhz crystal is needed to obtain the correct
      video rates for PC monitors displaying 640x480 screens. The 36Mhz
      crystal is used to obtain higher resolution modes, like 800x600x16
      colours.

  A3000
      This can generate seperate syncs but requires links to be set to
      determine the polarity. It has only a 24Mhz crystal and can
      therefore only drive 'forgiving' monitors correctly that don't
      mind the 640x480 video mode timings being slightly incorect.

      In order to obtain proper timings, and software control of the
      sync polarity, you will need a VGA VIDC Enhancer for the A3000.

  A400 series.
      The situation gets more complex. Due to an 'error' in the PCB
      / circuit diagram, the A400 series cannot generate seperate
      syncs satisfactorly. The video signal loses the green component
      when seperate syncs is selected.

      As standard, there is no polarity control over the syncs. In
      common with the A3000, there is only a 24Mhz crystal.

      If the PC monitor can handle composite syncs then the monitor
      can be used in 640x480 mode only.

  A300 series.
      Most, if not all, of the A300 series had the circuit board
      hardwired into composite mode continously. There is only a 24Mhz
      crystal, and only composite PC VGA monitors can be used.

Conclusion:
  Apart from the A5000 and newer machines, no computer as standard can drive
either a fixed frequency or multi-frequency PC monitor in all of the Archimedes
modes satisfactorily. However VIDC enhancer boards can be bought to upgrade an
Archimedes to handle the needed timing and signals.
----------------------------------------------------------------------------
Q18) What is ADFSBuffers and what is the best setting for it?

   ADFSBuffers are Read Ahead and Write Behind buffers for ADFS on your
Archimedes. These are designed to improve the speed of filing operations by
doing work at optimum times. There are some side effects of using them though.
When active under Risc OS v2.00 and v2.01 discs *must* be dismounted before
being removed from the floppy drive. Failure to do so results in the dreaded
'FileCore in use.' error. However if you are prepared to sacrifice the speed
improvment they give configuring the buffers to 0 does remove this problem. (Or
so I am informed.)

   Under Risc OS v3.00, as supplied with the early A5000 machines, these
buffers generate a different problem and must *always* be configured off.
Failure to do so results in spurious errors when using the Hard Drive on an
early A5000. Symptoms include reformating of crucial sectors of the disc, disc
address errors and general failure to save files to the drive. So when using
an A5000 with Risc OS 3.00 remember to configure them to off!

   With Risc OS v3.10 all of the old problems have been cured with a new one
introduced. Namely that if you have only a few ADFSBuffers configured and are
accessing the floppy drive then your machine can occasionally lock up
completely for you. It appears that any value of ADFSBuffers above 8 causes
that problem to be largely alleviated (read it only occurs rarely at these
settings). So under Risc OS 3.1 it is reccomended that you set your ADFSBuffers
to 8+. There is a patch module available, called ADFSUtils, that does fix this
problem - contact your local dealer for a copy of it.

   As for the optimum settings for ADFSBuffers, as far as I am aware no one has
done any speed tests to see what is the best setting. Presumably though Acorn
will have arranged for the system to start up (Well except for RO3.00...) in
the optimum state for most uses. I would be interested in anyone who has done
speed tests sending me the results of their investigations....

----------------------------------------------------------------------------
Q19) What is the current File-type allocation ranges and why won't Acorn
provide a full file-type list?

   Acorn have reallocated the File-type ranges for applications. The new
ranges are :-

  Non-user area

    &E00-&FFF   Acorn
    &B00-&DFF   Commercial software
    &A00-&AFF   Acornsoft, and other commercial software
    &400-&9FF   Commercial Software

  User area

    &100-&3FF   Non-commercial distributed software (ie PD)
    &000-&0FF   User's personal usage (ie non-distributed)

75% of the user area is for PD/Shareware, with allocations co-ordinated by
Acorn. If your software is going to be distributed, you should have an allocated
filetype to avoid clashes.

   Acorn cannot publish it's master list of filetypes because, at any given
time, it will contain allocations made for products which have not yet been
announced. Therefore, Acorn would be in breach of confidence by doing so -
and the editing overhead for producing a sanitised list is too great.

----------------------------------------------------------------------------
Q20) My disc gives me a 'Broken Directory' or my Free Space Map is corrupt,
      what can I do?

   Unfortunately due to the highly complicated nature of the filing system
data there is little that can be done easily. Your simplest and best way of
correcting the problem is to backup as much software as you can and reformat
your drive, restoring everything from those backups you make regularly...
(What you don't back up your discs? :-) ) To do anything else requires a
good knowledge of how the underlying structures work and is beyond the scope
of this FAQ, although this detail is covered in the Risc OS 3 PRMs.

----------------------------------------------------------------------------
Q21) My hard drive gives me disc errors when I use, what do the error
      numbers mean?

   The error numbers returned indicate the type of error encountered.
Exactly why slightly more meaningful messages are not returned I am unsure.
The error codes meanings are as follows :-

   06 unit select signal has not been returned by drive
   07 write fault signal from drive
   08 drive not ready
   09 seek complete has not been returned
   10 data error has been detected by ECC (Error Correction Code)
   13 a fatal ECC error has occurred in DATA area
   16 sector ID has not been found
   17 an ID area that begins with an improper address mark has been detected
   18 the address mark in DATA has not been detected

----------------------------------------------------------------------------
Q22) What does the power on self-test check and how does it signal errors
      back to you?

   The purple screen at power on indicates that the self-test has begun. A
brief ROM, RAM, VIDC and IOC test is performed and then the screen colour
changes to blue and a full memory test is performed, along with a second
test of the VIDC and IOC.  When the screen returns to purple, the machine is
testing for an ARM3.  At the end of this sequence the screen colour is set
to green (for pass) or red (for fail).  If the tests have all passed then
the machine starts to boot and the RISC OS 3 welcome screen is displayed.

   If any test fails, the screen will remain red and the disc drive light
will blink a fault code.  A short flash is used to indicate a binary '0' and
a long flash indicates a binary '1'.  The bits are grouped into eight
nybbles (blocks of four bits) with the most significant bit first.

   The lowest seven bits are a status word.  The meaning of each bit is
given below in hex :-

00000001   Self-test due to power on
00000002   Self-test due to interface hardware
00000004   Self-test due to test link
00000008   Long memory test performed
00000010   ARM 3 fitted
00000020   Long memory test disabled
00000040   PC-style IO world detected

   Bits 8-31 indicate the fault code and are described below.  Not all the
bits are used.

00000200   ROM failed checksum test
00000400   MEMC CAM mapping failed
00000800   MEMC protection failed
00004000   VIDC Virq (video interrupt) timing failed
00008000   VIDC Sirq (sound interrupt) timing failed
00020000   RAM control line failure
00040000   Long RAM test failure

----------------------------------------------------------------------------
Q23) Is there a Modula 2 compiler for the Arc?

   Currently, no. Acorn did have, in the early days of the experimental ARM
work, an in house compiler. However this compiler was sufficiently unstable
and buggy to be unreleasable as commercial product and was only used because
in house support was available immediately to the users of the compiler.
When Olivetti invested in Acorn this technology went to them so that Acorn
no longer have even an in house Modula 2 compiler.

   However some companies have stated intentions to produce Modula 2
compilers for the Arc. Whether these intentions become reality has yet to
be seen.
----------------------------------------------------------------------------
Q24) Is Virtual Memory possible under RiscOS?

   Short answer, full VM is *not* possible under the current versions of
RiscOS. The problem is that most of RiscOS works in SVC mode, if a DataFetch
abort occurs then R14_svc *is* corrupted. This makes returning from the SWI
somewhat problematic. This is a hardware limitation with the ARM2 and ARM3
cell chips. Future hardware using ARM6 or better processor cells have
special memory abort modes that alleviate this problem so future machines
and incarnations of RiscOS may well have VM available.

   However limited solutions are available now. !Virtual is one such
solution allowing VM for a user process using a limited subset of SWI's
that are carefully 'protected' against R14_svc being corrupted. Such
solutions suffer from the restricted set of SWI's they support and are
mostly useful for batch style processing jobs like compilation or
memory intensive processing jobs.
----------------------------------------------------------------------------
Q25) How compatible with other systems is an Archimedes?

PC :- The Archimedes can handle DOS discs (720k; the A5000 and later
models can also handle 1.44M floppies). In RO3, this is built in, under
RO2 you have to use one of the (PD) utilities.  There are two PC
(software) emulators that can handle most PC software, three if you count
the fact that Acorn's offering is split into two emulator programs. There
are also PC cards, containing an 80x86 processor and other PC hardware,
which uses the Archimedes' disc and video. All emulators are multitasking
(and not PD).

Unix :- Unix software can be ported (and in fact many packages already
have been) with the help of UnixLib, which is PD.  Memory-hungry ports,
such as gcc, can be run with the aid of !Virtual (also PD). Of course if
your really desperate to run Unix software it might be advisable to buy
RiscIx, the Acorn flavour of Unix.

Mac :- Due to the pecularities of the double density Mac disc format it is
difficult to read the Mac disc directly. However a company is releasing a
filing system and drive combination to read Mac high density discs allowing
transfers. Also Macs often can read PC format discs allowing transfers to
occur using that medium. There is no Mac emulator available.

Atari ST :- Like PC floppies, the Archimedes can read, write and format
ST-format floppies.  No emulator for the ST is known.

Amiga :- The amiga uses an unusual disc format that is not easily read by
other machines. Accordingly there is currently no Amiga format disc reader
available. But Amiga's can read PC discs, so again transfers can occur via
that medium. There is no Amiga emulator.

Spectrum :- There seem to be a couple of Spectrum emulators around, but
(according to rumour) they can't be distributed legally because they
require the contents of the ROMs, and Sinclair still holds the
copyright.

----------------------------------------------------------------------------
   Thanks go to all the people who have contributed corrections and
additions to the list. Without this help this list would be a hell of alot
buggier (spot the programmer... :-) ) than it is...
----------------------------------------------------------------------------
All additions, corrections & suggestions for the FAQ List should be sent to
                -=> banks_p@kosmos.wcc.govt.nz <=-
Being the maintainer of this FAQ I reserve the right to be wrong, incorrect,
     slow, out of date and generally how I please with the FAQ List.