The 729 CE manual quotes 555 BPI. I?m not sure when it became 556. http://bitsavers.trailing-edge.com/pdf/ibm/magtape/729/223-6845_729_CEman_1…
The IBM 728 was 248 BPI. Before that it was the nice round number 200 BPI.
I tried permutations of standard IPS and round number data rates and don?t see anything that yields exactly 556BPI.
Tim
> Jon Elson
> How/where should I submit this?
This is now available through here:
http://gunkies.org/wiki/Term-Mite_ST_Smart_Terminal
I put in a little infrastructure around it (articles on the Term-Mite, NS405,
etc), using info I dug up online.
Noel
> From: Toby Thain
> It's suggested there (without any proof though) that the CDC used a
> Fourier process
> ...
> I'd be very interested to know what you find out about the circuitry.
Someone very kindly pointed me at:
http://www.bitsavers.org/pdf/cdc/cyber/cyber_70/fieldEngr/60125000C_6602_66…
(although why it's in the Cyber70 folder, I'm not quite sure :-). I don't
completely understand it (it's only drawings, no text, and the notation is
unfamiliar), but I think I get the general drift - and it's pretty baroque!
Very briefly, it appears to me that characters are generated from short
vector-type strokes placed in a 7x7 matrix, with each stroke being encoded as
motion of 0, 1 or 2 'boxes', both horizontally and vertically, from the 'box'
of the end of the previous stroke. A character can contain up to 22 strokes,
but most seem to average about dozen or so.
The pronounced rounding which I noticed in the characters must be caused by
the limited bandpass of the A-D system, amplifiers, etc - it can't actually do
a sharp corner when going from e.g. a vertical stroke to a diagonal one. Or
something like that.. :-)
Noel
Inspecting a newly acquired HP 2392A I found out the chassis was prone to
whiskering all over the chassis.
Whiskers are small metal hairs growing from pure metal (zinc or tin) and can
when they connect to a power line create a shortage and electric arc
damaging the electronics.
Made some pictures and placed them in:
https://www.flickr.com/photos/hp-fix/41897770664/in/dateposted-public/
It's best to remove them by using scotch brite or fine sanding paper, after
that paint or coat the chassis with a clear paint or other nonconducting
paint.
More info about whiskering can be found at:
https://nepp.nasa.gov/whisker/https://en.wikipedia.org/wiki/Whisker_%28metallurgy%29
-Rik
While cleaning out my office, I found a brand new, unopened copy
of WRQ Reflection 4+ version 5.0 for DOS. It provides (per the
box):
Accurate emulation of Digital VT340, VT320, VT220, VT241, VT102,
and VT52 terminals, with VT420 features.
Windows-like interface with pull-down menus and dialog boxes.
132-column display with EGA, VGA, or special video adapters.
Full keyboard mapping and mouse support.
Etc., etc., etc.
If anyone wants it, just let me know and I'll send it to you in
exchange for the cost of postage (weighs 8 pounds). Otherwise
I will toss it in the recycle bin next week.
Alan "Pack Rat" Frisbie
All,
I have a need at work for an unusual SRAM chip (related to the New Horizons mission).
if you have a source or supply of these parts:
Part #=5962H9954103QXC
Qty=2 (per board)
Description: SRAM 256K x 8
Package=FPK40
Generic part#=LM2M8CRH-Q30X
with which you?d be willing to part for a good cause, we would really like to know about it!
Please contact me off-list, either by email or phone below, and I?ll happily put you in contact with the right folks.
- Mark
210-522-6025 office 210-379-4635 cell
I have two rare desktop telephones taking up space in my basement. I know I
never will play with or display them.
- Pingtel Xpressa PX-1. An early IP telephone
- ATT 8130 "Computer Phone". It has an RS-232 port in the back for
bi-directional comms. I reverse engineered the protocol when I used this in
1996. Crappy software available on request. I may even be able to dig up
the code Larry Wall sent me (Perl, of course) from the same era.
Photos here:
https://photos.google.com/share/AF1QipMJ-iCRhnHmiL9PoswsyJ2fiNTMK5Lw1xf
5TgpYr6UAo6ktLFAe6yEds5XvCIDoCg?key=WldvcDZnNEFlMmNza25ZLUdsN205R24zcFV2MHNR
Local pickup on Long Island or Manhattan, NY. I will mail it to you if you
pay the shipping via paypal or google pay. I will weigh it and calculate
the shipping if there is interest, but I am not going to bother unless
someone is interested.
On Mon, Jun 4, 2018 at 5:13 PM, Paul Koning via cctalk
<cctalk at classiccmp.org> wrote:
>> On Jun 4, 2018, at 1:17 PM, Robert Armstrong via cctalk <cctalk at classiccmp.org> wrote:
>>
>> ... FWIW, I have a 725 complete and working. Well, except for the RC25, which never worked even when they were new.
I had an 11/725 in the 80s and 90s and never had a problem with the
RC25 but they are legendarily terrible.
> Hm. I remember some RC25s on RSTS, and they seemed to be ok. The fact that they had two drives on one motor made it strange, especially if the fixed platter was your system device. We had to teach the OS how to deal with SY: going away temporarily.
Oof, yeah. When I used my 725, I didn't spin the RC25 up and down
except when booting and shutting down. I also had devices like RL02s
for removable storage.
I often wonder how hard it would be to develop some other storage
device for the KELSI but then other projects push to the top of the
stack and I move on.
Mostly, what I need is affordable ($250 or less) Unibus storage with
modern media (Flash or IDE adapter or whatever). I don't really care
what form it takes but Unibus SCSI cards are quite pricey and making a
new controller is even less affordable (I used to make and support
DMA-enabled Unibus communication controllers for a living so I have a
pretty good idea of the amount of effort required).
-ethan
List:
This is one that's bothered me for most of my adult life. As you may or
may not know, there were three industry standard densities for 7 track
1/2" tape: 200, 556 and finally 800 cpi/bpi.
So 200 and 800 are nice decimal multiples of 10. But 556 doesn't fit
that pattern--it's not a "nice' number, being the product of 4 and 139
and doesn't correspond to any computer-related characteristics that I
know of. It's not metric. So why 556 and not 400, 512 or 600?
There's got to be a story there, somewhere. I think the 556 density
came in around the 1401/7090 time with the 729 II.
Anyone know the story?
--Chuck
> From: Ethan Dicks
> Mostly, what I need is affordable ($250 or less) Unibus storage with
> modern media
There's this:
http://www.retrocmp.com/projects/unibone
Not quite there yet, but getting there.
Noel
