Re: rectangular sense core vs. diagonal

[Chuck Guzis via cctalk]

On 06/08/2017 01:08 AM, Christian Corti via cctalk wrote:

> 
> I got two ECS modules, I put pictures of them on my FB album. I've also
> put them on our server right now, at
> ftp://computermuseum.informatik.uni-stuttgart.de/cdc/ecs/
> 
> The core planes are *huge*, about 4000cm² !

Thanks for that--I never got to see the inside of one of those.

The simplicity of construction brings up another old memory about CDC
using separate facilities to produce ECS; in particular, the joke about
the "Tijuana Core House"...

--Chuck

Re: rectangular sense core vs. diagonal

[Mike Stein via cctalk]

- Original Message - 
From: "Fred Cisin via cctalk" <cctalk@classiccmp.org>
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk@classiccmp.org>
Sent: Thursday, June 08, 2017 10:39 AM
Subject: Re: rectangular sense core vs. diagonal


> On Thu, 8 Jun 2017, Mike Stein via cctalk wrote:
>> Another reason why things were better in "The Good Old Days":
>> While removing a (spring-loaded) microSD card from a tablet yesterday my 
>> fingernail slipped and 32 Gigabytes of data shot out and disappeared 
>> somewhere among the dust bunnies behind my desk; that could never have 
>> happened with these core modules!
> 
> What would have happened if 32 Gigabytes of data fell on your desk?
--
Need more info: How many bytes in one of those modules, how thick are they 
(i.e. cm3 instead of 4000 cm2) and what does one weigh?

I don't think it would be pretty though...

It still boggles my mind that you can put a Terabyte of data on a card the size 
of a postage stamp, with 2 TB around the corner...

Re: rectangular sense core vs. diagonal

[Norman Jaffe via cctalk]

There'd be no desk, just dust. 

From: "cctalk" <cctalk@classiccmp.org> 
To: "cctalk" <cctalk@classiccmp.org> 
Sent: Thursday, June 8, 2017 7:39:40 AM 
Subject: Re: rectangular sense core vs. diagonal 

On Thu, 8 Jun 2017, Mike Stein via cctalk wrote: 
> Another reason why things were better in "The Good Old Days": 
> While removing a (spring-loaded) microSD card from a tablet yesterday my 
> fingernail slipped and 32 Gigabytes of data shot out and disappeared 
> somewhere among the dust bunnies behind my desk; that could never have 
> happened with these core modules! 

What would have happened if 32 Gigabytes of data fell on your desk? 

Re: rectangular sense core vs. diagonal

[Fred Cisin via cctalk]

On Thu, 8 Jun 2017, Mike Stein via cctalk wrote:

Another reason why things were better in "The Good Old Days":
While removing a (spring-loaded) microSD card from a tablet yesterday my 
fingernail slipped and 32 Gigabytes of data shot out and disappeared 
somewhere among the dust bunnies behind my desk; that could never have 
happened with these core modules!


What would have happened if 32 Gigabytes of data fell on your desk?

Re: rectangular sense core vs. diagonal

[Mike Stein via cctalk]

- Original Message - 
From: "Christian Corti via cctalk" <cctalk@classiccmp.org>
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk@classiccmp.org>
Sent: Thursday, June 08, 2017 4:08 AM
Subject: Re: rectangular sense core vs. diagonal


> On Wed, 7 Jun 2017, Paul Koning wrote:
>>> How is ECS constructed?   I fooled with a lot of it back in the day, but
>>> never got a good look at the core planes.
>>
>> I'd love to know.  I never saw the insides of ECS.  There are some 
>> documents on Bitsavers but none that I have seen show the ECS memory 
>> subsystem itself, certainly not at the circuit level.
> 
> I got two ECS modules, I put pictures of them on my FB album. I've 
> also put them on our server right now, at
> ftp://computermuseum.informatik.uni-stuttgart.de/cdc/ecs/
> 
> The core planes are *huge*, about 4000cm² !
> 
> Christian
--
Another reason why things were better in "The Good Old Days":

While removing a (spring-loaded) microSD card from a tablet yesterday my 
fingernail slipped and 32 Gigabytes of data shot out and disappeared somewhere 
among the dust bunnies behind my desk; that could never have happened with 
these core modules!

Re: rectangular sense core vs. diagonal

[dwight via cctalk]

This is more like DRAM. There are bit lines and word lines.

All the address decoding is done outside the array.

No X Y partial addresses.

Instead of having one plain for each bit, the bits are all in the single plane.

Dwight



From: cctalk <cctalk-boun...@classiccmp.org> on behalf of Christian Corti via 
cctalk <cctalk@classiccmp.org>
Sent: Thursday, June 8, 2017 1:08:19 AM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: rectangular sense core vs. diagonal

On Wed, 7 Jun 2017, Paul Koning wrote:
>> How is ECS constructed?   I fooled with a lot of it back in the day, but
>> never got a good look at the core planes.
>
> I'd love to know.  I never saw the insides of ECS.  There are some
> documents on Bitsavers but none that I have seen show the ECS memory
> subsystem itself, certainly not at the circuit level.

I got two ECS modules, I put pictures of them on my FB album. I've
also put them on our server right now, at
ftp://computermuseum.informatik.uni-stuttgart.de/cdc/ecs/

The core planes are *huge*, about 4000cm² !

Christian

Re: rectangular sense core vs. diagonal

[Christian Corti via cctalk]

On Wed, 7 Jun 2017, Paul Koning wrote:

How is ECS constructed?   I fooled with a lot of it back in the day, but
never got a good look at the core planes.


I'd love to know.  I never saw the insides of ECS.  There are some 
documents on Bitsavers but none that I have seen show the ECS memory 
subsystem itself, certainly not at the circuit level.


I got two ECS modules, I put pictures of them on my FB album. I've 
also put them on our server right now, at

ftp://computermuseum.informatik.uni-stuttgart.de/cdc/ecs/

The core planes are *huge*, about 4000cm² !

Christian

Re: rectangular sense core vs. diagonal

[Paul Koning via cctalk]

> On Jun 7, 2017, at 3:24 PM, Chuck Guzis via cctech  
> wrote:
> 
> On 06/07/2017 10:47 AM, Paul Koning via cctech wrote:
> 
>> 6600 core memory is documented in great detail in the training manual
>> which is on Bitsavers.  It has conventional diagonal sense lines.  It
>> does have some interesting design attributes, though.  For one thing,
>> it has pairs of inhibit wires each carrying half the inhibit current.
>> Also, there are four X inhibit and four Y inhibit lines, so you use
>> four of the address bits to select which inhibit "quadrant" is
>> driven.  The manual doesn't say why; I believe it is done to limit
>> the inductance and to keep the per-wire inductance roughly consistent
>> for the select (X and Y) and inhibit (X and Y) wires.  The drive
>> circuitry is also interesting, featuring constant currents that are
>> steered between an idling inductor and the selected wire, rather than
>> being switched on.  All these techniques seem to explain the very
>> high performance -- full read/restore cycle in about 800 ns, which in
>> 1964 was way faster than what others were doing.
> 
> How is ECS constructed?   I fooled with a lot of it back in the day, but
> never got a good look at the core planes.

I'd love to know.  I never saw the insides of ECS.  There are some documents on 
Bitsavers but none that I have seen show the ECS memory subsystem itself, 
certainly not at the circuit level.

By the way, the memory chapter of the 6600 training manual is very much worth 
reading carefully.  It has some very clever circuits in it, and trying to 
reason through in your head why things are done a certain way is a lot of fun.

paul

Re: rectangular sense core vs. diagonal

[Chuck Guzis via cctalk]

On 06/07/2017 05:02 PM, Paul Koning wrote:

> I'd love to know.  I never saw the insides of ECS.  There are some
> documents on Bitsavers but none that I have seen show the ECS memory
> subsystem itself, certainly not at the circuit level.

I found a paper from SJCC 1967 that does a pretty good job of explaining
things.  The surprising thing is that ECS is a "two wire" system.

https://www.computer.org/csdl/proceedings/afips/1967/5069/00/50690729.pdf

--Chuck

Re: rectangular sense core vs. diagonal

[Chuck Guzis via cctalk]

On 06/07/2017 10:47 AM, Paul Koning via cctech wrote:

> 6600 core memory is documented in great detail in the training manual
> which is on Bitsavers.  It has conventional diagonal sense lines.  It
> does have some interesting design attributes, though.  For one thing,
> it has pairs of inhibit wires each carrying half the inhibit current.
> Also, there are four X inhibit and four Y inhibit lines, so you use
> four of the address bits to select which inhibit "quadrant" is
> driven.  The manual doesn't say why; I believe it is done to limit
> the inductance and to keep the per-wire inductance roughly consistent
> for the select (X and Y) and inhibit (X and Y) wires.  The drive
> circuitry is also interesting, featuring constant currents that are
> steered between an idling inductor and the selected wire, rather than
> being switched on.  All these techniques seem to explain the very
> high performance -- full read/restore cycle in about 800 ns, which in
> 1964 was way faster than what others were doing.

How is ECS constructed?   I fooled with a lot of it back in the day, but
never got a good look at the core planes.

--Chuck

Re: rectangular sense core vs. diagonal

[Brent Hilpert via cctalk]

On 2017-Jun-07, at 7:12 AM, william degnan via cctalk wrote:
> Where there any computers that used a "rectangular sense" core RAM?
> Whirlwind core is diagonal.   This page describes the differences/evolution
> of the sense line.
> 
> More: http://ed-thelen.org/comp-hist/Byte/76jul.html
> 
> Were rectangular core planes used in any commercial/government computer
> that saw production activity, presumably the period 1953-1959?Whirlwind
> is known for diagonal sense planes, but was there a brief period when the
> core was "rectangular sense"
> 
>  I know core was added to Whirlwind as an
> upgrade, it did not launch into production with core.  (right?)


From what the author writes, the memory he is examining uses rectangular sense 
in a 4-wire arrangement, so the Spectra-70 would be one computer to look to.

Whirlwind started with a holding-beam memory (form of CRT storage-tube).
The problems with that inspired Jay Forrestor (whirlwind director) to come up 
with something better and resulted in the development of core memory.
That original form of core design was 4-wire with diagonal sense.

I don't know how early the rectangular sense topology was developed but with 
tighter & more complex control requirements I'd guess it was not in the 
vacuum-tube era.

'Rectangular sense' is inherent in 3-wire core memories (have to disagree with 
Jon there.) 
The sense wire being parallel to one axis of address wires makes it possible 
for it to do double duty as the inhibit wire, and so eliminate the threading of 
a fourth wire.

In my observation, the 3-wire format came in somewhere around the very late 
60s/1970.
For example, according to the maintenance manuals, the pdp-8/i (1968) is 4-wire 
diagonal sense, the pdp-8/e (1970) is 3-wire rectangular sense.
The HP2116 versions saw a similar development timeline for the memory.
I think I can say most to nearly all of the core memories of the 70s were 
3-wire and hence rectangular sense,
although I've seen one example of a smaller memory from 1974 still using 
diagonal sense.

Speculating in part, but It would make sense as the development history:

1. Original diagonal sense as the easier & more obvious way to minimise 
capacitive  & inductive coupling.

2. Somebody developed the rectangular sense, probably to help simplify 
the threading.

3. Somebody noticed the now parallel address & sense wires would allow 
combing the sense & inhibit wires, coming up with the 3-wire arrangement and 
simplifying manufacturing considerably.

Re: rectangular sense core vs. diagonal

[Paul Koning via cctalk]

> On Jun 7, 2017, at 1:01 PM, Jon Elson via cctech  
> wrote:
> 
> On 06/07/2017 09:12 AM, william degnan via cctech wrote:
>> Where there any computers that used a "rectangular sense" core RAM?
>> Whirlwind core is diagonal.   This page describes the differences/evolution
>> of the sense line.
>> 
>> More: http://ed-thelen.org/comp-hist/Byte/76jul.html
>> 
>> Were rectangular core planes used in any commercial/government computer
>> that saw production activity, presumably the period 1953-1959?Whirlwind
>> is known for diagonal sense planes, but was there a brief period when the
>> core was "rectangular sense"  I know core was added to Whirlwind as an
>> upgrade, it did not launch into production with core.  (right?)
>> 
>> 
> I think IBM LCS on the mid-scale 360s were rectangular.  I assume by 
> rectangular you mean that all wires were on a rectangular grid, parallel to 
> the select wires.  The google article on core memory shows a CDC 6600 core 
> plane that shows no sign of diagonal wires.

Are you talking about the Wikipedia article, the photo of the 6600 core memory? 
 That photo is severely misleading.  The "inset" is something entirely 
different.

6600 core memory is documented in great detail in the training manual which is 
on Bitsavers.  It has conventional diagonal sense lines.  It does have some 
interesting design attributes, though.  For one thing, it has pairs of inhibit 
wires each carrying half the inhibit current.  Also, there are four X inhibit 
and four Y inhibit lines, so you use four of the address bits to select which 
inhibit "quadrant" is driven.  The manual doesn't say why; I believe it is done 
to limit the inductance and to keep the per-wire inductance roughly consistent 
for the select (X and Y) and inhibit (X and Y) wires.  The drive circuitry is 
also interesting, featuring constant currents that are steered between an 
idling inductor and the selected wire, rather than being switched on.  All 
these techniques seem to explain the very high performance -- full read/restore 
cycle in about 800 ns, which in 1964 was way faster than what others were doing.

> I think many old core planes with big cores ran all wires on a square grid, 
> as there was plenty of window area in the cores.  When they went to smaller 
> cores and combining the sense/inhibit winding, then the diagonal wire 
> threaded more easily through the remaining window after the X and Y select 
> wires were in place.

Normal layout is what the Wikipedia article shows: wires in X/Y direction for 
the most part, cores at 45 degrees.  The sense wires normally zigzag along the 
diagonals.

One detail not often described (I found it called out in the EL-X8 training 
manual) is that the sense wire routing is done so that it passes through cores 
in alternating direction for any given row and column.  The point of doing so 
is that then the noise pulses from half-selected cores in the addressed row and 
column very nearly cancel.

On the "inset" memory with just two wires: that's prpobably CDC 6000 series ECS 
memory.  That was slow (4.8 microsecond cycle) very large memory, 488 bit 
words.  The CDC manuals describe it as "word select".  The text near that photo 
describes the approach briefly (it would be nice to have more details).  I 
vaguely remember a photo showing a large rectangular core plane -- not clear 
just how big, 256 by 488 would be a possibility, or 488 by 1024.  If so, it 
would be bits of the word arranged along one coordinate, word addresses along 
the other.

paul

Re: rectangular sense core vs. diagonal

[Jon Elson via cctalk]

On 06/07/2017 09:12 AM, william degnan via cctech wrote:

Where there any computers that used a "rectangular sense" core RAM?
Whirlwind core is diagonal.   This page describes the differences/evolution
of the sense line.

More: http://ed-thelen.org/comp-hist/Byte/76jul.html

Were rectangular core planes used in any commercial/government computer
that saw production activity, presumably the period 1953-1959?Whirlwind
is known for diagonal sense planes, but was there a brief period when the
core was "rectangular sense"  I know core was added to Whirlwind as an
upgrade, it did not launch into production with core.  (right?)


I think IBM LCS on the mid-scale 360s were rectangular.  I 
assume by rectangular you mean that all wires were on a 
rectangular grid, parallel to the select wires.  The google 
article on core memory shows a CDC 6600 core plane that 
shows no sign of diagonal wires.


I think many old core planes with big cores ran all wires on 
a square grid, as there was plenty of window area in the 
cores.  When they went to smaller cores and combining the 
sense/inhibit winding, then the diagonal wire threaded more 
easily through the remaining window after the X and Y select 
wires were in place.


Jon

rectangular sense core vs. diagonal

[william degnan via cctalk]

Where there any computers that used a "rectangular sense" core RAM?
Whirlwind core is diagonal.   This page describes the differences/evolution
of the sense line.

More: http://ed-thelen.org/comp-hist/Byte/76jul.html

Were rectangular core planes used in any commercial/government computer
that saw production activity, presumably the period 1953-1959?Whirlwind
is known for diagonal sense planes, but was there a brief period when the
core was "rectangular sense"  I know core was added to Whirlwind as an
upgrade, it did not launch into production with core.  (right?)

Thanks.

Bill