>From: "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
>
>On Mon, 2005-03-14 at 23:51 +0100, Nico de Jong wrote:
>> The fact is, that the development of drives is so quick, that even if you
>> _could_ save a tape or disk or CD or whatever for 30 years, you wouldnt find
>> the proper drive, and even if you did, it wouldnt be supported anymore.
>> Let's go back 30 years; what were the dominant media at that time ? 1600 bpi
>> reel-to-reel tapes, 7.25 or 30 MB harddisk (IBM 2311/2314), and 8" floppy
>> discs. Some of my customers _still_ accept 8" disks and reels for financial
>> transactions.
>
>Philosophical question. As performance of a device goes up, does the
>need for more performance (by the average user) go down?
>
>In other words do we hit a point where the storage technology of the day
>is so good for what the typical/power user needs that there is no
>incentive for manufacturers to built anything better?
>
>Curious as to what people think. I'm sure they'll always be innovation
>in the lab and on specialist high-budget projects, but maybe one day
>they'll just be nowhere left to go for Joe Public.
HI
Hardly. The requirement for more space will continue. Serial
data, such as CDROM's have some limits coming up but not
the hunger for more data space. Access time is becoming a
limiting factor that technology will sortly overcome( or we
are doomed ).
Dwight
I am the scoundrel that made the original post on this
topic that opened a flood of discussion. Members brought
up details that I never addressed; and I learned from
everyone's posts. Thank you! This may be useless, beating
a dead horse, and off topic. I am re-submitting here my original
6 point comment with corrections and links, and with ADDITIONS
as points: 7, 8, 9, 10, 11, and 12 to cover other areas people
have brought up, etc.
Richard Bristol
----------------------------------------------------------
Archival longevity of DVD and CD media may be a good topic
for the computer preservationist. I have studied this quite a bit.
My first conclusion, including from crude accelerated life
and torture tests I made myself, is that the "100 year" claims
some people made are likely baloney. A research article appeared
in the German version of Q't magazine (unless I miss-spelled
that), where they did some tests on raw error rate on just
burned DVD+R media, using some $50,000 equipment. None of the media
they tested had a low enough raw error rate to meet the requirements
of the DVD+R standard. Yet they sell it. (Mitsubishi did the best.)
Then there are many hobbiests looking at raw error rates on DVD
media using Lite-On drives with firmware than can report on
raw errors. For example, hobbiests measure and post on sites like:
http://www.cdrinfo.com/Sections/Reviews/Print.aspx?ArticleId=11657
My overall conclusion is that most DVD media on the
market sold by no-names, and by the names Sony, Maxell, Memorex,
3M Imation, etc is not very good. These companies re-badge
whaterver is cheapest this month from whatever factory. My
least favorite factory is CMC Magnetics Corporation in Europe.
Next worst in my view are some Korean and Taiwanese factories
(K-Well, In Young, and Lead Data=Great Quality=GQ). TDK seems to
be the only advertised brand that makes their own DVD-R that you
can actually buy in a USA retail store (although one member said
maybe they don't make it themselves), unless the store carries Verbatim.
I just verified that Pioneer and Verbatim buy their media from the
good Japanese companies, Mitsubishi (MCC), Taiyo Yuden (TY), and Mitsui.
Anyway, Pioneer and Verbatim consistently have low raw error rates.
A low error rate when freshly burned gives greater margin that
as the errors increase as the media ages, error correction can
still take care of it. Also, these companies have better engineering
about the life span of the organic dyes and such used in the
data layer. So when I want it to last, I do this:
1) Use a good burner with low raw error rate after burn/read and
good media-to-other-machine cross compatibility. I used to
recommend the Pioneer DVR-105 and below, but the DVR-107 and
DVR-108 are poor at this. Now I recommend BenQ DW1620 ($52)
DVD+-RW double layer drive. Most burners have new firmware you
can flash even if you bought it yesterday. A lot of the effort
in the new firmware is decreasing the error rate on some media,
so it is often worth flashing it.
2) My first choice of media is either Pioneer or Verbatim DVD-R,
followed by DVD+R from the same two makers. Third choice brand
is TDK. I don't trust much else. Double sided and double layer
DVD are a little imature at this point.
3) The freeware Windoze program DVDinfo.exe will tell you who made
your mysterious media (reads it off the media). E.g. MCC001 is
made by Mitsubishi.
4) All RW media (DVD-RW DVD+RW CD-RW) have poor archival life.
Think about it: with RW, instead of burning a pit in the data
layer, you are fooling around with glossy or matte finish
depending on how quickly a melted liquid re-freezes. Official
tests, and my own tests, show poor life. A little sunlight-UV
can erase it.
5) I don't burn more than 85% of the capacity of a DVD. DVDs are
a sandwich, lexan (polycarbonate) on both sides, data layer
chemistry in the middle. The spiral starts on the inside (opposite
LP records). If you leave 3/4" unused at the outside edge, it
will take longer before the Ozone and 02 and other environmental
exposures that attack the data chemistry at the edges of the
lexan sandwitch actually reach your data. So on a "4.7GB" disk
which in real life could hold 4.3GB, I burn 3.8GB.
6) DVD-R or DVD+R is better than CD-R, because it is a sandwich.
DVD also has stronger error correction. CD-R often dies from
the label side, by getting bumped against the drive tray,
the jewel case, a pen... The paint layer that protects your data on
the label side is very thin and fragile. CD-R also die from chemical
errosion from ozone, fingers, marking pens, etc on the label side.
I write on them only in the center no-data area. DVDs, being
a sandwich, don't have those problems.
7) If you really care about it's archival life, hedge your bets
by burning two copies, on DIFFERENT media. Select two good
media types made by different companies. Each may have, just
a guess, a 10% chance of self-destructing within 20 years.
This would be because of a design or implimentation mistake.
For example perhaps the sandwich adheasive includes a chemical
that eventually reacts badly with the data, or some impurity
in manufacturing at that time. If the two media are very
different, their probabilty of failure approaches statistical
indpendence; and if independent then the chance that both are
unreadable would approach 0.1 * 0.1 or only a 1% chance.
8) Because the data is sandwiched in plastic, my belief is that
single-layer single-sided DVD-R or DVD+R as a class will last longer
then CD-R as a class. However, some applications require CD-R.
For archival CD-R I have used extensively and can recommend
"BASF by EMTEC" (Emtec in USA) "Ceram Guard" CD-R BASF CD-R74
Maxima Ceram DA (really made by Taiyo Yuden). (Beware some
different Emtec/Basf CD-R are made by CMC and are poor.)
However "Ceram Guard" is truely hard to buy in the USA. I bought
mine for $2 each from the retail chain "Guitar Center" in person
(guitarcenter.com). They were marked "for audio use" but that does
not matter. They are NOT gold. Their feature is that a ceramic
coating is vacumn sputter-coated on the labeled. You could probably
use a ball point pen on it. They are by a mile the most sturdy
CD-R I have ever seen. Unlike most CD-R, taps to the label side
don't kill them. Out of about 1000 CD-R I have seen or used "in the
field", I have seen about 25 dead CD-R's (that were once good)
And 22 of those 25 were at least slightly abused. (Sun, moisture,
tap on drive tray on label side when inserting, or tap on jewel case)
Only 3 of 25 appeared to die from purely with "from the inside bit rot".
Of those 3, 2 were made by one company: GQ Great Quality, Taiwan. So
I am mostly interested in the label side coating.
These ceramic coated disks are mentioned here:
http://www.cdmediaworld.com/hardware/cdrom/basf.shtml
BASF/Emtec also sells these as "archival" but I would want to know
who made it for them before buying. They are real gold:
BASF/Emtec CD-R Gold Digital Photo
BASF/Emtec DVD+R Digital Video Gold
Occasionally you can find "Kodak InfoGuard". They are expensive. They
have a very tough label side, and use gold. They are semi-discontinued,
and were sold to medical and business markets. If you have a Kodak
"Picture CD" from film processing you may have one there.
Kodak digital science InfoGuard, maker: Kodak Japan Limited,
Phthalocyanine 1X - 4X
Kodak Gold Ultima InfoGuard, maker: Kodak Japan Limited,
Phthalocyanine 1X - 4X
More practically speaking, you CAN actually buy Mitsui "MAM Gold CD-R"
for about $1 each now. They use real gold, and have a decent
paint layer they call "diamond coat". (But it's not anywhere
near the toughness of "Ceram Guard" or even "InfoGuard".)
Described for sale here:
http://store.mam-a-store.com/standard---archive-gold.html
9) I don't know if high-spin readers contribute to media death. But
too high a speed definitely contributes to "can't read Table of
Contents" and "ECC Error" on read, and marginal quality burns.
Plextor CD-R burners come with PlexTools(?) software specifically
to slow them down. You can sometimes read a CD-R this way that
otherwise can't be read on newer faster readers. To read a
CD-R whose errors are too high for most all readers, I prefer
these to read it: Plextor 4x CD-RW drive, or 12x (not 8x).
Plextor 20x and above are not as good. Cheap and I have a
few: Panasonic 12x just plain reader. Sometimes other 4x readers
by NEC, Panasonic, Pioneer, Sony.
10) I like to try, when burning, for the lowest raw-error-rate (that
some machines can tell you when you read). Published tests show
excessive speed hurts. My rule of thumb when burning is:
Never exceed the lesser of the media's rated speed, or 2/3 of
the burner's maximum speed. So if a CD-R burner will burn at 48x,
and the media says it is 80x, I will burn it at around 12x or 24x.
There is such a thing as too slow also, for a particular burner.
The sweet spot gives you a lower raw error rate, and greater
cross-compatibility when reading it on many different drives.
11) A disk that takes a long time to "settle" (usually light goes
out) on insertion is a possible indication of a high error rate
and likelyhood of complete table of contents failure later.
12) The free Windoze program md5summer.exe will generate a text
file with .md5 ending for any directory tree of files. Each line
in the file is the md5, a space, *, and then the pathname;
one line per file. I put one of these .md5 files in the top
level of my CD-R or DVD-R burns. Then, in Windoze a couple years
later, double click that .md5 file and it does the
opposite, and confirms the md5 of each file on the media.
I have seen a few CD-Rs that were damaged, that in Windoze gave no
error message at all when read, but the data read back was
actually wrong. I use md5summer also before ftp etc. transfers.
Will someone better informed say how this is best done and
commonly done in linux and unix? Perhaps
find . -exec md5sum '{}' \; > md5sum_list
or something? And the checking later?
Richard Bristol (the same guy who recently asked for
help reading 9-track tar tapes)
On Wed, 16 Mar 2005 22:00:12 -0800, Zane H. Healy <healyzh at aracnet.com> wrote:
> At 9:32 PM -0800 3/16/05, Cameron Kaiser wrote:
> >Does anyone know a true (not a homebrew hack) multitasking environment that
> >will run in 16K or less, preferably with available source?
> >
uCOS-II. (http://www.ucos-ii.com)
Real-time, pre-emptive multitasking, embedded.
Comes with source-code, have to buy the book to be legal.
Heck it even has a TCP/IP module.
Quote (page 72) of the said book:
"A minimal kernel for an 8-bit CPU that provides only scheduling,
context switching, semaphore management, delays and timeouts should
require about 1 to 3kB or code space."
So theoretically it'd be possible to port this to a 16kW PDP.
So now that I've got the 8" drive running well on the PC, I am trying to
read 8" CP/M disks. 22Disk is giving me sector not found errors
(cylinder 2, side 0, sector 1) and the DOS CP/M tools are giving me
"Unknown floppy disk format", even on disks that read fine on my NEC APC.
I tried reading in a sector using debug but I also get read errors.
Any ideas?
The drive is a Tandon TM 848-02. Very little information online, but it
seems to support DSDD.
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
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Richard Bristol wrote:
> (5) I don't burn more than 85% of the capacity
> of a DVD. DVDs are a sandwich, lexan (polycarbonate)
> on both sides, data layer chemistry in the middle.
> The spiral starts on the inside (opposite LP records).
> If you leave 3/4" unused at the outside edge, it will
> take longer before the Ozone and 02 and other environmental
> exposures that attack the data chemistry at the edges
> of the lexan sandwitch actually reach your data. So on
> a "4.7GB" disk which in real life could hold 4.3GB, I
> burn 3.8GB.
Interesting approach.
Curious though ... why do the edges get attacked first? Are the disks
slapped together in some sort of fashion such that there exists a potential
breach at the edges?
Eric wrote:
> However, I don't *really* think you want to spend the rest of your
> life writing your own FPGA development software. It's a hard problem
> and there are hundreds of thousands of man-years of development effort
> in the Xilinx software. By the time you got your own software working
> for one family, that family would have long since been discontinued.
Scott wrote:
> I would suspect that while there might be hundreds of thousands of man
> hours, that there just can't possible be hundreds of thousands of man
> *years* involved.
On Mar 16 2005, 17:53, der Mouse wrote:
> Well, I've never had a cap in a power supply go bang. But I did once
> put together a circuit and carelessly use a cap rated for about half
> the expected voltage - I was checking only the capacitance, my bad.
I've had two electrolytics fail spectacularly.
The first was one that had just aged. It was a large PSU electrolytic
in a valve[1] PA amplifier. I'd had the amp running several times, for
an hour or so at a time, but on one occasion, it just blew. It made a
loud hissing noise, and ejected a stream of white fumes.
The second was a non-polarised electrolytic in an Atari monitor. The
original had failed, so I looked through the catalogues for a similar
type. The only one I found of the same capacitance and voltage claimed
to have a suitably large ripple current capacity, but was quite a lot
smaller than the original. I was a bit skeptical, but hey, technology
moves on and capacitors get smaller every year, right? It lasted about
90 seconds. The bang was spectacular, and the amount of fibrous
padding that came out of such a small space was really impressive. The
ceiling still has the dent in it, but the monitor now has a
polypropylene cap instead.
[1] British for "vacuum tube"
--
Pete Peter Turnbull
Network Manager
University of York
> Can I easily test the mechanics, on/off switches, lamps, motors,
> etc, without hooking up the TC11? I think there is a local
> mode switch and wondered what all could be tested easily
> without hooking up the TC11. I will be studying the documentation
> to get a better idea about things. I have a TC11 that also needs
> to be cleaned up. It has a layer of dust on it and needs a couple
> boards, which should be here soon.
>
I am also hoping to start firing up my PDP-8 and TU56 in the next few weeks [the lab is almost re-built!!!!!] so perhaps Ashley and I could coordinate our (limited) knowledge and run various tests in parallel....
You will probably need to pull the hubs and clean and lubricate the spring
loaded friction bushing behind the hubs. If you turn it by hand and it
is quite stiff or springs back after you release the hub then they need
cleaning. Most of the hubs are screws in the plastic so a easy to strip
when tightining so don't over do it. They may come pre stripped. The manual
goes into how to put the hubs on. Try somewhat tight and if they slip
tighten some more. The screws are serrated head so may need to be
replaced if slipping and worn. A little slipping won't hurt for initial
testing but will wear the shaft long term. I used some epoxy thread
repair material since some of mine were prestripped. It sort of worked
but wasn't really strong enough. Putting in a helicoil might be better
but I didn't go that far.
The tape motion can be tested in local mode and the manual has adjustments
for clean stopping. When no tape in installed both reels should turn in
opposite directions. With a tape on it should not turn until you hit
forward or backward.
The lights may be burned out. They were sold as assemblies but they are
a custom order now. You can open them up and carefully solder in a new
bulb inside. I bought a couple similar bulbs from Mouser and picked the
one I liked. Since mine had no good bulbs I can't say what was the closest
match.
The capacitors have been discussed. The 4 motor capacitors are obvious if
they are going, junk will be coming out the vent. Altough after shipping it
may of all broken loose. The power supply in the back also has a big
capacitor in it for the motor drive voltage (36V?). It wouldn't hurt to
reform that one. I haven't always reformed the capacitors most of the time
its powered up ok but did have them fail in one item. I use the current
limited supply method.
Also note you provide either 5V or 10V, not both.
I have a video of operation of my unit online if you need to see what
it looks like running.
David Gesswein
http://www.pdp8.net/ -- Run an old computer with blinkenlights.
Have any PDP-8 stuff you're willing to part with?
Hi,
I have returned to my HP9915B that blows its fuse as soon as you
power it up.
I followed Tony's advice and checked the two large capacitors (C46
and C58), and the PIC645 and they are all OK. I then checked the
U30 (3524) in the chopper sense circuit and its OK as well.
I checked the parts after removing them from the PCB to ensure that
there was no interference by other components.
So now I am really at a loss and wonder if anybody has any ideas.
Best Regards
**vp
