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The Fred Fish Collection 1.5
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TrackSalve
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Manual
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1990-06-12
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218 lines
TRACKSALVE
TrackSalve is made to improve the Trackdisk device. TD has some
problems and lacks some options. As far as I know there are three bugs,
from which one is very bad if more than one drive is connected.
SetPatch 1.3.2 tries to do something about it, but it is not enough.
There are people who do not like the sound of an empty drive. Trackdisk
cannot handle a track with an error on it. Then all data on that track
is lost. We never know whether the just written data is well stored on
disk. Some programs do not switch off the motor. And yet we are poking
in Trackdisk, we can just as well make a drive optional readonly.
FUNCTIONS
As already stated, TrackSalve can perform six functions:
1. Standard modification of Trackdisk existing of: Bugs patched. The
patch of the bugs (as far as I know them). These are the
TD_RAWREAD/TD_RAWWRITE bug and the NoDisk routine (oef!). Now it is save
to do I/O on one drive and let all your other drives empty. Write to
protected disk returns an error, and leaves the unit undisturbed.
Prewrite mfm update. Before a track is written back to disk, all timing
bits are validated again. This is to prevent the declining of never
updated sectors on much used tracks. New coding routines. Now it is
possible to use fast memory to do I/O. This has no obvious function
now, but imagine the effects when adopted by Commodore and the
Filesystem with AddBuffers. If you have fast memory, you can use the
FastFileBuffer program to change the buffertype.
2. Noclick. Can be switched on and off for each drive apart. I think the
situation is as follows: Some drives have an electrical switch at the
home position to prevent stepping below zero. Other types have a
mechanical stop. These you cannot get completely silent. I think it
is save to use noclick on the first. For those with a mechanical stop
I would not switch noclick on.
3. Readonly simulation. Each drive can act as if the tab of the inserted
disk is open. This is not as simple as it sounds. The FileSystem
(DOS) keeps track of disk swapping. And it asumes that you are not
able to shift the tab while a disk is in the drive. Therefore IF there
is a disk in the drive AND its tab is closed (write-enabled), and the
drive is swithed over to read-only or read/write, a DiskChange is sent
out. This is very unfriendly during a write, so this is delayed until
the motor is switched off. Nevertheless, switch a drive from r/w to ro
or back only when it is quiet.
4. TrackSalvage. If Trackdisk gives up on a track, this function (if
enabled) comes to action. The track is read again and analised. All
unsuspicious data is recovered and stored in Trackdisk's buffers. If
the requested data is recovered, no error is passed to the calling
task. But an attempt to write to this track is denied and results into
a diskerror. So faulting tracks are readonly.
5. Verify. TrackSalve can read back a just written track to check whether
the data well arrived on disk. It reads the track into a special
buffer which is compared with the original write buffer. Since the
Amiga is multitasking, it is not possible to know which task should be
notified about an error. Therefore it is the user who must decide
about this. He can choose between rewrite and ignore. Rewrite writes
the original buffer again to disk, and ignore as if we never knew about
the bad track. It may be that subsequent rewrites does not lead to a
good result. At least the fact is known that something is wrong. It
is possible to read-retry by repeating the command: v read only once,
vv twice and vvv triple, subsequent v's are ignored. Multiple reads
for verify may be useful for usage with very bad drives.
6. Auto update. The write to disk is delayed until the trackbuffer is
needed for another track or until an update command is received. The
motor also keeps running until a motor off command is received.
TrackSalve can both do by itself if this function is enabled. It is
delayed for about five seconds, that is, the track is updated five
seconds after the last write command. The motor is switched off five
seconds after the last disk access. Especially Sectorama (which was
intended for harddisks) will be helped with this function. But there
are more. (Diskcopy: try to diskcopy to a write protected disk).
COMMANDLINE
If anywhere on the command line one of the chars h, H, or ? are found,
the whole command line is ignored and nothing is done but a small usage
explanation is printed:
Syntax: TrackSalve {[!]<unit>|a {<unit>} {<Command>}}
Function: Modify a Trackdisk device unit addressed by its unit number
<no args> Show present status
Units:
0-3 Unit(s) Succeeding commands are applied to listed units
a All Succeeding commands are applied to all TD units
! Warning Suppress error if the following unit does not exist
Commands:
<none> TD in RAM No special functions (.=default), improved reliability
o Original Let TD execute in its original ROM code
s SectorDisk Let Trackdisk only give errors from bad sectors
t .TrackDisk Normal: Let TD give errors from bad tracks
n NoClick Perform noclick on the unit(s)
c .Click Normal: No noclick
r ReadOnly Make unit read-only, simulate open disk-tab
w .WriteEnable Normal: Unit is read/write according to disk-tab
v Verify Read written track back and compare (vv, vvv)
b .Believe Normal: Asume track is written well
u Update Flush track and stop motor after 5 sec idling
e .ExtUpdate Normal: External update and motor off
/ Separator E.g. "0/2n" Units 0 and 2 in RAM, noclick only on 2
h ? Explain If given (anywhere), no commands are executed
Comma's, spaces and dashes are completly ignored. Characters which are
not defined lead to an abortion of the program without executing any
function. This will be emphasised by a message via standard out.
Abortion always has a return value of 20.
Units
You must address an unit by its number instead of its DOS-name. This
is because we are modifying an Exec-device and not a DOS-device. This
device has nothing to do with DOS. DOS uses it, and builds a system
around it. The name of this system is for example "DF0:". Valid
numbers are 0, 1, 2, 3, a and A or any combination of them. 'A' means
all units. Commands are single characters. Before you give a command
you must specify one or more units to apply the command to. A command
will be passed to all directly preceding listed units. If a unit is
given that does not exist, then this is an error and nothing will be
done at all. It can come handy if it is possible to give a unit that
does not exist. Normal would be aborted with return code 20. But if
a '!' is put before a possible non-existing unit, a message is printed
and the program continues normally, but returns 5.
Commands
Just a list of units and no commands results in the execution of
Trackdisk in RAM with repaired bugs. "TrackSalve a" or "TrackSalve
023". Commands are applied only to preceding units. F.e. TrackSalve
01n lets units 0 and 1 stop clicking. Now you can add new unit numbers
like: TrackSalve 01n2r1s. This results into noclick on units 0 and 1,
unit is 2 readonly and unit can salve tracks. It is also possible to
give contradictory commands: TrackSalve an1c lets all units except 1
noclicking. The separator '/' is a donoting command or "unit list
reset". TrackSalve 012/2n lets the units 0, 1 and 2 execute in ram, but
noclick is only performed by unit 2. Reset to a defined state can be
done by TrackSalve ao followed by the new state. TrackSalve without
any parameters prints the present situation and changes nothing.
HOW TO USE IT
Although Disksalv works well without, both programs work very well
together. Disksalv with TrackSalve will generally operate faster and
more clearly. It also is possible (not yet happened) that the
combination can salve more data. Sometimes only one file is the effort
of salvage worthy, like the latest modification not yet on a backup.
Now there is a chance that the file can be saved with copy. Might save
some time. Then it is possible that immediately after disk insertion a
requester appears with "unreadable" and "diskdoctor" or so. There is a
fair chance that with TrackSalve these requesters stay away and the
disk will be accepted as a DOS disk. You can do more in that case.
IMPLEMENTATION
The Trackdisk code will be copied from the operating system program and
modified and extended. For each unit apart, the unit task can execute
this code or stay with the original in ROM. If a unit cannot be brought
to execute the patched code, this is told in a message on standard out
and the program will continue normally but its return value will be 10.
There are two functions which use a buffer of about 26k. If not
available at the moment of enabling, every .5 second this is tried to
allocate again. Until the allocation is successful, the function
becomes not active. This is reported through a message and the return
value will be 10. Execute TrackSalve without parameters to be sure the
function became active. This buffer is shared among all tasks.
Normally this will work smoothly and without delay except when a
requester is displayed. The requester is used when a verify error has
been detected. If for some reason it is not possible to pop up a
requester, TrackSalve will loop rewriting the track and blink the
drive's led until the conditions have changed. These are:
1. The disk is removed.
2. The track is found well on disk.
3. There is enough memory to display the requester.
PERFORMANCE
The mfm revalidation costs some time. It is not an exact value, but it
will stay well under 2 procent. The encoding routines and track
maintenance became much faster because these can now ignore the timing
bits. Track verify takes a lot of time, but it is done very efficient
this close to the object. I measured an average increase of 30 procent.
To get these results, I did a file level diskcopy of a 70 procent full
disk to a duplicate.
HISTORY
Version 1.0 had a guru 3 type bug, but the faulting code was (almost)
never executed. This version could be updated to 1.01 by a patch
program PatchTS.
Version 1.2 had multiple reads with verify implemented for users with
very bad drives.
Version 1.3 had mfm revalilidation adopted from Pcopy, new coding and
decoding routines allowing fast buffers and auto update implemented.
Also a write to a write protected disk is denied. Verify comparision
is now done by the blitter. And a unit is more likely to be caught.
COPYRIGHT
Copyright (c) 1990 D.W.Reisig. This program may be distributed on
non-commercial base. This program may not be distibuted on commercial
base without my permission.
D.W.Reisig
Woudweeren 10
1151 AV Broek in Waterland
Holland