I am attempting to back up some floppies from a project I did a few years ago.
The sets of 3.5" 1.44Mb IBM floppies have been stored in a box, in a cool and
dry room. Out of one set of 12 and one set of 15 disks, I have four disks
that have read errors that DOS won't get past, bad sectors and the like.
I know that circa 1993, these disks were good. They were written once, mailed
to me, loaded once and put away. I would like to preserve the data because it
has some small historic significance. It's not earth-shattering if the data
is gone forever, but those of us who play adventure games would lose a little
link to the past. I do not belive that the client still has copies of this
original data, so that's not an option. The project eventually made it to
market, so it's not a "lost" game or anything; but these disks do represent
a work in progress with some interesting bugs.
Are there any tools to go divining on DOS floppies that work better than
an endless succession of "R"etries? It's an all or nothing prospect; the
first disk has the install file, the remaning disks have a chopped monolithic
data file. If one disk can't be read, the whole set is fundamentally useless.
Thanks for any suggestions.
-ethan
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As I recall, all the undocumented operations have the two ls bits set. Is
that correct? Maybe I should add them to my assembler/debugger.
The one I routinely hear about the Z-80 is one which places the odd parity
of the bytes (or maybe the lsb's of the bytes) in a block moved with an LDIR
or INIR instruction into the carry or some such. This instruction is
supposed to leave carry unaffected, but doesn't.
Dick
-----Original Message-----
From: Hans Franke <Hans.Franke(a)mch20.sbs.de>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Saturday, April 17, 1999 10:15 AM
Subject: Re: z80 timing... 6502 timing
>> Were you aware of the neat little opcodes that were built into the 6502?
I
>> don't have my list of them any more, but back in the KIM days, there were
>> several lists in circulation. As I recall, one of them was a double
load,
>> i.e it loaded a value into both a register and the accumulator. I
believe
>> another loaded a register and pushed the value on the stack at the same
>> time. Esoteric, for sure, but you never know . . .
>
>Like SHIFT&OR (0F,1F,1B,...), ROL&AND (2F,3F,3B,...), LSR&XOR
($F,5F,5B,...),
>ROR&ADD (6F,7F,7B,...) etc ... most are realy exotic and save only a second
>instruction, but some could have been a big help, if they had been official
>(like AND A,X and STORE, without changing A or X - saving up to 4
instructions,
>or LOAD A&X, or AND MEM&X/MEM&Y). Some are more or less useles, like the
STOP
>(halts execution, only reset will wake up the CPU) or just longer NOPs (two
and
>tree cycles).
>
>THe 65xx stuff is quite known, but what has been new to my ears are the
>8085 'hidden' operations.
>
>Gruss
>H.
>
>--
>Stimm gegen SPAM: http://www.politik-digital.de/spam/de/
>Vote against SPAM: http://www.politik-digital.de/spam/en/
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>Ich denke, also bin ich, also gut
>HRK
Xebec made a number of "specialized" bridge controllers, which fit between
the host adapter, which is what you've described, in this case possibly
intended to go to a compatible version of their 14xx-series controllers
which, in turn, provides a SCSI interface to an ST506 drive, which you
apparently have on hand.
It is likely that the 26-pin connector is to the Apple II version of SCSI
which was put out back then on a 25-pin DB-25 connector.
I recently got a drive with a Xebec label on its enclosure, having bought it
for the enclosure, and found the drive had an integrated adapter on it which
was terninated in a DC-37 connector, not unlike what was on the early
Bernoulli Boxes from IOMEGA. I didn't investigate the pinout or anything,
naturally, since I don't care about small drives like this. There's
probably a similar version for this card's interface as well.
Dick
-----Original Message-----
From: Pete Turnbull <pete(a)dunnington.u-net.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Saturday, April 17, 1999 9:45 AM
Subject: Apple HAL XEBEC controller
>One of today's acquisitions is a small card for an Apple ][ (or Apple ///),
>labelled "APPLE 2/3 XEBEC INTERFACE REV 1".
>
>I happen to have a couple of old Xebec ST412 winchester controllers, so I'd
>like to try this out.
>
>Can anyone tell me the pinout of the 26-pin header at the end of the card?
> Pins 3,7,11,15,17,19,21,23,25 are grounded, the other seventeen seem to be
>signal lines. Pins 1,5,9,13,20 are high impedance; the other even-numbered
>pins are terminated by a 220/330R resistor pack.
>
>Does it need any other software (like a formatting disk)? The on-board 4K
>EPROM contains only the strings "(C) HAL COMPUTERS LTD 1983", "A/XHAL
>SHARED RESOURCE WINCHESTER SYSTEM", "NOT CONNECTED", and "SRS ERROR", so I
>guess there would have been a floppy with it, originally.
>
>--
>
>Pete Peter Turnbull
> Dept. of Computer Science
> University of York
On 9 Apr 1999, ard(a)p850ug1.demon.co.uk (Tony Duell) wrote:
...
] A ROM _is_ combinatorial logic. I don't want to get into a silly argument
] over this, but I have great difficulty finding a conceptual difference
] between a combinatorial circuit built from a pile of AND, OR and NOT
] gates and the same circuit built (albeit using a lot more transistors) in
] a ROM. To claim that a CPU using a ROM is microcoded but one with
] _identical_ internal states using simple gates as the feedback logic
] round the sequencer flip-flops is not is a very strange way of thinking
] about things.
Request accepted; silly argument follows. (Oh, you said "don't"?
Oh well, too late.)
Do you mean to say that _all_ computers are microcoded? After all,
the control logic can always be modelled by some number of state FFs
and a large-enough ROM, couldn't it? Or is your claim that there is
no such thing as microcoding? That strikes me as far-fetched as well.
The difference is that a ROM is easily replaceable; slap in another ROM
or EPROM with different microcode burned in, and you've got an entirely
different machine on your hands. Maybe to you it is just as easy to
redesign some section of the circuit board, etch a new one, pull the
newly required chips from your very-deep storage bin, and Bingo! you're
done. For most of us, I suspect that sounds like quite a lot of effort.
I don't think anybody ever claimed that microcoded machines could do
things that non-microcoded machine could not, or vice-versa. It is
a matter of convenience. And maybe there is some added comfort level
for software geeks, using a (micro)program to control everything, and
being able to alter it just like any other software (or firmware).
I guess it is exactly the added (and admittedly wasted in any fixed
design) transistors, just sitting there unused, waiting to be assigned
work, that makes microcoding attractive - it is easier to adjust
precisely because you don't have to muck around with how many transistors
are in there, or worry about board-space/power-consumption/fanout/etc/etc
that you might have to worry about if you wanted to adjust some hard-
wired discrete logic.
Bill.
(Gee, that didn't turn out to be nearly as silly as I had expected.)
Hi,
Could anyone tell me how a radio detects signals vs. static? There is a
little gauge on my radio that moves depending on the amount of noise vs.
signal. I would guess that the digitally tuned radios that skip over the
frequencies that are pure static work in the same way. What is this way?
--Max Eskin (max82(a)surfree.com)
http://scivault.hypermart.net: Ignorance is Impotence - Knowledge is Power
Were you aware of the neat little opcodes that were built into the 6502? I
don't have my list of them any more, but back in the KIM days, there were
several lists in circulation. As I recall, one of them was a double load,
i.e it loaded a value into both a register and the accumulator. I believe
another loaded a register and pushed the value on the stack at the same
time. Esoteric, for sure, but you never know . . .
Dick
-----Original Message-----
From: Hans Franke <Hans.Franke(a)mch20.sbs.de>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Saturday, April 17, 1999 9:27 AM
Subject: Re: z80 timing... 6502 timing
>> <65C02, because it was buillt in several conflicting versions. What
about
>> <the Z-80 core? Whose? Which one? Speed, of course, should be
"limited" t
>> <whatever was available in 1982. That certainly includes the Synertek
(MOS
>
>> In 1982 all of the z80s in the market had the same hidden features
>> including the IX/IY 8bit ops. I know of no z80 that didn't have them.
>> Not all of them were available to the 6mhz spec though many could be
>> pushed. Also allowed is the 8085 (available as a 5-6mhz part then).
Again
>> all of the 8085s had the extra unsupported instructions as they were deem
>> important!
>
>a) The speed (of a particular CPU) used is not important for this, since
>(I assume) we all can handle the transformation - the goal is still the
>factor to use to judge the relative power.
>b) unsupported OPCs in the 8085 ? Did I miss them ? I did 2 years of
>8085 development projects, and never heared of (also of course never
>used) - can you tell what they where alike ?
>
>Gruss
>H.
>
>--
>Stimm gegen SPAM: http://www.politik-digital.de/spam/de/
>Vote against SPAM: http://www.politik-digital.de/spam/en/
>Votez contre le SPAM: http://www.politik-digital.de/spam/fr/
>Ich denke, also bin ich, also gut
>HRK
William Donzelli
>If people want to send _way_ off topic stuff to this list, my requests are
>articles about ice fishing, reprints of old Home & Garden magazines, or
>hardcore pornography.
For the right price I can get you hardcore porn of women ice fishing with
copies of Home & Garden. ;)
--
Gareth Knight
Amiga Interactive Guide | ICQ No. 24185856
http://welcome.to/aig | "Shine on your star"
<I think you are spot on there, I am led to believe the 60hz decision in th
<US and some other countries was made to facilitate the use of the
<(relatively) precise mains frequency for clocks and other timing functions
<This is also possible, even for motor driven clocks, with 50hz mains simpl
<by careful motor design. Though it may have been less simple when the
<decision was made.
makes no difference save for one item...
<equivalent to the mains frequency. This reduces/eliminates mains hum
<strobing, though it is more of a historical problem with modern TV designs
<think.
No, more of a problem with OLD designs.
The key item is that motors and transformers are physically smaller
for same or similar VA capability with increasing frequency. there is a
corner you turn as you go higher though as the iron in the course gets
lossier and line radiation increses losses. So power distrubution has
the 50/60 as a good bet. Note aircraft use 400nz for the compact
transformers and reduced filtering in rectifiec circuits. There were also
25, 30 and 40hz systems. The NY subway at one time was 25Hz and the DEC
mill prior to refurb in the 80s was 40hz (that power also lighted part of
the town.) at one point in history.
Allison
It might, in fact, be interesting to see what limitations/enhancements the
hardware features of the two processor types would impose. Interleaved
display memory would effect both processors' ability to use memory, etc.
I'd say it will difficult enough to come up with a problems suitable for a
valid exercise without such difficulties.
Dick
-----Original Message-----
From: Hans Franke <Hans.Franke(a)mch20.sbs.de>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Saturday, April 17, 1999 7:19 AM
Subject: Coding chanllange (was: z80 timing... 6502 timing)
>> > >Ooh! A machine code competition. I'm in! I'll do the 6502 and whoop
>> > >EVERYONE'S ass!
>
>> > And then you woke up. First what are the rules, 6502 or 65C02, code in
Rom
>> > or Ram, what is the code supposed to do?
>
>Good point.
>
>> > My vote goes for something with some graphical element so we can "see"
what
>> > is happening. (spinning ball, etc.)
>
>Nice, but already to high level.
>The task should be abstract enough to run within a simple
>system, lets say a SBC system with CPU, some MEM and some
>of the usual I/O&Controll stuff (Ports, Serial, Timer).
>
>Basicly there are two types of possible challanges:
>a) implements some kind of standard code in a most speedy way, or
>b) build some small, but sophisticated "real world" application.
>
>Challenge a) would meet the basic idea we had in our discusion:
>define at what ratio two processors are equivalent when executing
>a real task, while b) should be sophisticated enough to give a
>'boh ey' (sound of exeptional admire) effect.
>
>In terms of a sportive competition a) would be a compulsatory
>exercise, while b) is more a voluntary (free style) exercise.
>
>As I stated before, for our theme a) would be more aprobiate.
>
>As actual tasks I would suggest
>for a): a 'simple' sorting challenge
>given is
>- Input media
>- Input structure
>- input data (same data or all participants, randomly generated)
>- Type of sort algo to use (what about just a bubble ? :)
>- Output structur
>- Output media
>the score schould be made up from
>Execution time (mainly for the sort, but also for I/O)
>Programm length (again most points to be given on the sort itself)
>Style (readability, portability, maintainability)
>
>for b) a thing like a small multi tasking OS could be used,
>maybe for a controlling application (heating or traffic -
>or what about a model railroad setup ?) or other purposes ?
>(This could be chalenging, since these kind of tasks are
>maybe a bit tough for our little helpers :)
>
>So, you're opinion ?
>
>> BRING IT ON, MO FO!
>> Don't rub the lamp if you don't want the genie to come out.
>
>MO FO ? I fear, I'll have to rub the lamp.
>
>Gruss
>H.
>
>--
>Stimm gegen SPAM: http://www.politik-digital.de/spam/de/
>Vote against SPAM: http://www.politik-digital.de/spam/en/
>Votez contre le SPAM: http://www.politik-digital.de/spam/fr/
>Ich denke, also bin ich, also gut
>HRK
> <> And then you woke up. First what are the rules, 6502 or 65C02, code in Ro
> <> or Ram, what is the code supposed to do?
> <>
> <> My vote goes for something with some graphical element so we can "see"
wh
> <> is happening. (spinning ball, etc.)
>
My vote would be to implement an algorithm.
Of course, which algorithm would a gruesome discussion.
Kelly
