Author Topic: Legacy Technology RAM Boards - A Question for UK Modders.  (Read 4966 times)

Offline Pete W.

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Legacy Technology RAM Boards - A Question for UK Modders.
« on: January 14, 2016, 04:52:43 AM »
Hi there, all,

I wrote 'all' but I guess this question is directed at UK Modders.

Back in August, 1980, I bought some printed circuit boards from the New Bear Computing Store in Newbury, Berkshire.  These boards, when populated, each supported 4 kB of static RAM, using 2102 or 21L02 chips plus some 'glue logic'.  The boards are physically similar in outline to those of the Motorola 'Exorciser' development system for the 6800 8-bit microprocessor.

Because of difficulties getting hold of other components for my project (e.g. a teleprinter as VDUs weren't available) I never assembled these RAM boards.  Amateur computer enthusiasts in those days didn't have access to stuff like keyboards, monitors and PSUs that have since become more easily available!

I still have both the boards and the 21L02 chips but I can't find any of the original New Bear circuit or assembly instructions.

So I'm posting this enquiry in case any other (UK) Modder still has any relevant New Bear documentation on file and would be prepared to copy or scan for me. 
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest design change-note!

Offline John Swift

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Re: Legacy Technology RAM Boards - A Question for UK Modders.
« Reply #1 on: January 14, 2016, 07:38:54 AM »

Hi Pete

just incase no one has the instructions for the  New Bear Computing  memory boards
widen the search to include other computers of that period

without the complication of dynamic refresh the boards will use a simple address decoding circuit that is likely to be very similar to other designs published in ETI , Practical electronics etc

http://ece-research.unm.edu/jimp/310/slides/8086_memory2.html

  John


Offline DMIOM

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Re: Legacy Technology RAM Boards - A Question for UK Modders.
« Reply #2 on: January 14, 2016, 11:26:26 AM »
Pete,

I can't help you directly, but there's another member - Trevor Brownen(sp?) - on here who might be able to give you some pointers. The gentleman's username on here is "trevoratxtal" and if I recall correctly he mentioned, in a thread when we were discussing NASCOM machines that he was involved (as the designer?) of systems in the 1970s and 1980s.

Dave

Offline DavidA

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Re: Legacy Technology RAM Boards - A Question for UK Modders.
« Reply #3 on: January 15, 2016, 06:24:58 AM »
You could also try asking on the Geekstogo website. I have always found them very helpful.

www.geekstogo.com

Dave.

Offline Pete W.

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Re: Legacy Technology RAM Boards - A Question for UK Modders.
« Reply #4 on: December 11, 2017, 12:53:35 PM »
Eureka!!!!

I knew, just knew, I must have the Newbear literature SOMEWHERE!!!

This afternoon, I searched through the filing cabinet and found it!!   :thumbup:   :thumbup:   :thumbup:  Halfway back in only the second drawer!

The search took quite a while but that was because I kept reading all the interesting long-forgotten stuff I wasn't looking for.   :ddb:   :ddb:   :ddb:

The schematic diagrams are on diazo dye-line print paper and have aged a bit but are still legible.  Maybe I'll have a go at re-drawing them in Fusion 360.

I got a 120 day warning when I started this reply but I thought I'd post anyway in case anyone else needs the data for these Newbear RAM boards.  Do you think a Google search for 'Newbear' would find this post?

Who knows how many milliamps 4 KB of 21L02 static RAM plus address logic would draw?   :lol:   :lol:   :lol:   :lol:   :lol: :lol:
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest design change-note!

Offline John Swift

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Re: Legacy Technology RAM Boards - A Question for UK Modders.
« Reply #5 on: December 11, 2017, 01:36:55 PM »

I guess you could work it out from this 2102  data sheet -

http://www.nteinc.com/specs/2100to2199/pdf/nte2102.pdf

with all inputs at 5V  it gives the supply current as 45mA

the current will increase when your reading and writing to it

as the Power Dissipation as 1W it
looks like the current could  increase  to 200mA during the R/W cycle

    John

Offline Pete W.

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Re: Legacy Technology RAM Boards - A Question for UK Modders.
« Reply #6 on: March 26, 2019, 11:20:03 AM »
Well, I managed to mislay the New Bear data but it turned up again yesterday!

The schematic diagram is an A2 diazo print but, with the help of our local print-shop, I've reduced it to an A4 print.  See pictures below.

I've also attached a copy of the New Bear assembly instructions. 

I've also tried to attach the same files in .pdf format but I'm getting an error message!

There are some hand annotations on the schematic diagram - I can't explain them at present.  I'll need to compare the schematic with the actual printed circuit board. 
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest design change-note!

Offline Pete W.

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Re: Legacy Technology RAM Boards - A Question for UK Modders.
« Reply #7 on: March 26, 2019, 01:08:45 PM »
Here's an attempt to attach a .pdf of the schematic diagram:

(Sorry, it's on its side!) 
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest design change-note!

Offline Pete W.

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Re: Legacy Technology RAM Boards - A Question for UK Modders.
« Reply #8 on: March 26, 2019, 01:20:10 PM »
And here's an attempt to attach the constructional details:

Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest design change-note!

Offline Pete W.

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Re: Legacy Technology RAM Boards - A Question for UK Modders.
« Reply #9 on: March 26, 2019, 01:44:34 PM »
I've scanned the printed circuit board.  The scans are attached.  They are, component side, reverse side and reverse side flipped left-to-right:

New Bear published a design for a 6800 based computer but that used a different format of pronted circuit board from the one shown here.  This board, as stated in the Constructional Details, is the same format as the Motorola MEK6800D1 evaluation kit and also that used in the larger professional 'Exorciser' system.  The principal physical dimensions are given on the schematic. 
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest design change-note!

Offline awemawson

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Re: Legacy Technology RAM Boards - A Question for UK Modders.
« Reply #10 on: March 26, 2019, 01:54:23 PM »
Is that an S100 format card Pete?

Looks very similar to one I used in my first 'proper' home made PC based on an S100 bus and a Z80 running CP/M - I  think it was a 'Tinker Toys' card that I had to import from the US.
Andrew Mawson
East Sussex

Offline Pete W.

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Re: Legacy Technology RAM Boards - A Question for UK Modders.
« Reply #11 on: March 26, 2019, 04:32:40 PM »
Hi there, Andrew,

An eBay seller in the USA sold a Motorola prototyping board - here is his reply to a question similar to yours:

Here is a prototyping board that fits the bus used on the Motorola MEK6800D1 and MEK6800D2 Microprocessor development boards.  I received this board in an S-100 purchase but was unsure of what it was as it definitely was not an S-100 board.  I came upon an eBay listing for a Motorola MEK6800D1 kit and I recognized the bus layout immediately as I had been trying to find the system it belong to for a while.

I have some more information courtesy of a kind eBay member:
 
This fit all of the MEK series the MEK6800D1&2, MEK6802D3, MEK6802D5, the Micro Chroma 68, The 68000 series MEK68KDM, etc. They were all made to be able to plug into the Motorola Exorciser systems. All with the same 43 edge connector pins (and basic pin out) on each side.

Thanks for looking at my auction!

I'll try to post a page giving the pin assignments tomorrow. 
 
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest design change-note!

Offline Pete W.

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Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest design change-note!