Re: how fast were drum memories?

[ANDY HOLT via cctalk]

 from  "Dave Wade via cctalk" 
To: "General Discussion: On-Topic and Off-Topic Posts" 
Sent: Thursday, 10 May, 2018 5:53:38 PM
Subject: RE: how fast were drum memories?

I don't think early drums were terribly fast, but this wasn't  a problem 
because often they were on serial machines, and the data had to sync with the 
clock speed of the machine.

I know that the Manchester Mk1 which evolved from the baby had a drum added. 
The design of the drum used changed as the machine evolved. There is some info 
on this evolution here. 

http://curation.cs.manchester.ac.uk/computer50/www.computer50.org/mark1/gethomas/manchester_drums.html

Its interesting to note that the size of the drum was decreased to around 6" as 
suggested by others.

The Ferranti Pegasus also had a drum for main storage and delay lines for 
"registers". 
This was a physically large drum with a capacity of 5120 40 it words.

The Ferranti Pegasus the clock speed was 333Khz and this was derived from clock 
tracks written on the drum avoiding any sync problems.
However in order to achieve this transfer rate the designers built the tracks 
in pairs with alternate bits coming from different tracks..
The large diameter of the drum gave problems getting consistent flying height 
for the heads, which resulted in large changes in signal level.



See 
https://archive.org/stream/bitsavers_icticl1900orageSep64_1140393/1962_Drum_Storage_Sep64_djvu.txt
for the spec on the 1962/3/4 drums for the ICT/ICL 1900 series
When we (City University) acquired our 1905E system (think it was ex Swansea 
uni.) it came with a 1964 drum (0.5M 24-bit words) made, I think, by Bryant.
Took up a lot of floor space and was probably the slowest of our peripherals to 
come up to "ready" from power on*

we "let it go" when we needed to install more equipment in the computer room - 
don't know what happened to it.

* the big CDC at ULCC had a huge drum† - but it had its problems - any 
power-off, even for a second or so, meant that it needed 
a full hour to be operational again.
† or, perhaps, a special fixed disk.

Andy

EF50 was Re: radar history

[ANDY HOLT via cctalk]

E = 6.3v filament
F = Pentode
5x = B9G base

Andy

Re: R: Large discs

[ANDY HOLT via cctalk]

"Is there a form of machine readable data older than 150 years?"

Jacquard cards;
Morse recorder;
certain musical instrument programmes.

Also with modern scanners virtually any printed material and some handwritten.

Andy

Re: Kennedy 9832 tape drive ( eBay 302562153660)

[ANDY HOLT via cctalk]

eBay Item 302562153660


Sure, it's a Kennedy 9832 drive mounted in some sort of giant hard case.
 Anyone know if this was a modified drive?  What on earth would it be
used for?

--Chuck

Can't see this item, ut
Tape drives in flight cases (which I assume is described) are normally data 
loggers or part thereof.

Re: Plotter + Tape drive

[ANDY HOLT via cctalk]

OK, I now have 4 expressions of interest.

If Philipp can arrange something in a reasonable timescale he has priority
Otherwise I think Peter Brown's collection from the Medway towns is likely to 
be best.
The other Peter from Ireland can be a reserve
and Dave Wade is definitely still interested but has deferred to Philipp and 
given timing difficulties should probably be a reserve.

Last chance for anyone else to join this list.

Andy


- Original Message -
From: "Peter Brown via cctalk" <cctalk@classiccmp.org>
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk@classiccmp.org>
Sent: Thursday, 17 August, 2017 6:32:17 PM
Subject: Re: Plotter + Tape drive

Hi Andy,

I too would be interested in the tape drive and plotter - I can collect 
postcode ME1, so not too far away

Regards

Peter




From: ANDY HOLT <andy.h...@tesco.net>
Sent: 16 August 2017 11:36
To: Philipp Hachtmann; General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Plotter + Tape drive

It is SCSI.
You are one of two people interested both of whom have transport problems.
I REALLY don't want to pack it for transport though there a few courier firms 
that could send it
collecting from here (I'd probably put DPD as the most reliable that knows this 
location)

If you're keen enough the way I might suggest if you're in a reasonably 
accessible part of Germany (Germany is a big place, Bavaria is probably too far)
would be to drive to Hook of Holland; take the ferry to Harwich; then drive 
here (Rayleigh Weir - less than an hour from Harwich)
then return in a similar manner. No idea whether air freight from Southend 
airport (less than 10Km from here) would be practical and affordable.

Don't commit to spending money until I have some more response from Dave Wade 
(other interested party)

Andy
>>>>
- Original Message -
From: "Philipp Hachtmann via cctalk" <cctalk@classiccmp.org>
To: "ANDY HOLT via cctalk" <cctalk@classiccmp.org>
Sent: Wednesday, 16 August, 2017 12:15:36 PM
Subject: Re: Plotter + Tape drive

Hi,

> HP 88780 9-track tape drive (also several tapes "new" in packaging).
> Both were working when last powered-on but that was a couple of years ago.
If the drive is the SCSI version, I'd be VERY () much interested!

I'm located in Germany. Must think how to get it here in case that I
could get it.

Kind regards

Philipp
<<<<

Re: Plotter + Tape drive

[ANDY HOLT via cctalk]

It is SCSI.
You are one of two people interested both of whom have transport problems.
I REALLY don't want to pack it for transport though there a few courier firms 
that could send it 
collecting from here (I'd probably put DPD as the most reliable that knows this 
location)

If you're keen enough the way I might suggest if you're in a reasonably 
accessible part of Germany (Germany is a big place, Bavaria is probably too far)
would be to drive to Hook of Holland; take the ferry to Harwich; then drive 
here (Rayleigh Weir - less than an hour from Harwich)
then return in a similar manner. No idea whether air freight from Southend 
airport (less than 10Km from here) would be practical and affordable.

Don't commit to spending money until I have some more response from Dave Wade 
(other interested party)

Andy
>>>>
- Original Message -
From: "Philipp Hachtmann via cctalk" <cctalk@classiccmp.org>
To: "ANDY HOLT via cctalk" <cctalk@classiccmp.org>
Sent: Wednesday, 16 August, 2017 12:15:36 PM
Subject: Re: Plotter + Tape drive

Hi,

> HP 88780 9-track tape drive (also several tapes "new" in packaging).
> Both were working when last powered-on but that was a couple of years ago.
If the drive is the SCSI version, I'd be VERY () much interested!

I'm located in Germany. Must think how to get it here in case that I 
could get it.

Kind regards

Philipp
<<<<

Plotter + Tape drive

[ANDY HOLT via cctalk]

Giving away ancient computer equipment (Essex England): 




I have a HP 7550A plotter and a 

HP 88780 9-track tape drive (also several tapes "new" in packaging). 

Both were working when last powered-on but that was a couple of years ago. 




I was going to give them to the computing history museum in Cambridge but they 
have had to decline for lack of space. 

If nobody claims and can collect from SS6 before the bank holiday (and 
preferably sooner!) they will go to the recycling centre (aka tip!) 

Warning - the tape drive is around 40Kg. 

I will also be offering these on another list. 

Soonest to collect has priority! 




Andy Holt 


ps Tony if you want these but cannot transport mail me and we'll see if a 
solution is possible. 

Re: 8mm cinemax type film players (almost OT)

[ANDY HOLT via cctalk]

I guess that depends on your opinion of "reasonable".

I have a number of 8mm home videos my father made but every place I looked
at was prohibitively expensive (several hundred dollars per reel!!)



Or on location, perhaps (I'm in the UK)
A few years ago I had mine and my fathers 8mm films transcribed and I don't 
think it cost more than £50 for about a dozen reels. (I certainly wouldn't have 
paid £100 a reel)

At that price the DIY solution seems the only reasonable one.
But beware of framing problems.

Andy

Re: 8mm cinemax type film players (almost OT)

[ANDY HOLT via cctalk]

My tape obsession was already slightly out of control, but when I found a 
create of 8mm reel of family footage and other movies in my 90 something year 
old grandfather's storage, I need a recommendation on how to play these, we're 
they standardised?

What is the difference between 8mm and super 8, is it backwards compatible?

Or is this all to analogue to care?


There are companies around who will transcribe 8mm (either form) to DVD for 
quite reasonable prices
(they'll almost certainly also do 16mm and may be able to do 9.5mm as well - I 
think "single 8" only differs from "standard 8" at the camera)

(remembering the days when I coveted a Bolex H8)

Andy

Re: Anybody has Control Data (CDC) disk packs for 841 and 844 disk drives to spare with?

[ANDY HOLT via cctalk]

I am looking for someone who can read an ICL EDS8 disk pack. I am told that it 
would have been used in an ICT type 2802/2 drive on an ICL 1905E, but that it 
is also compatible with an IBM 2311 disk drive and that it uses a mechanical 
assembly based on a CDC 9450. Given the mention of the 2311 above, I wonder if 
this means that you have facilities to read an EDS8 pack?

It might be similar to a 2311 but it's not quite the same.
In modern terminology the ICL uses hard sectors whereas the IBM uses soft 
sectors.

ICL calls sectors "buckets" and there are 8 128 word buckets to a track. (A 
word being 24 bits = 4 characters)
If I remember correctly (see if I can find a copy of the programmers reference 
manual) cylinder 0 is the directory; 
 on UDAS executives (that 1905E would probably have run E6RM) the next three 
(?) cylinders are normally reserved for Exec overlays.
I think George3 behaved similarly except that it had its own directory 
structure that mapped onto the drive directory in some manner.

I would think it "not too difficult" to build a modern controller that could 
read that pack on either type of drive – interpreting the results might be 
trickier.

Andy