Please identify this circuit board
dkelvey at hotmail.com
Wed Feb 1 13:02:21 CST 2017
I think it is a register board. Something
to hold data through a power down.
From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Paul Koning <paulkoning at comcast.net>
Sent: Wednesday, February 1, 2017 10:06:55 AM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Please identify this circuit board
> On Feb 1, 2017, at 1:02 PM, Paul Koning <paulkoning at comcast.net> wrote:
>> On Feb 1, 2017, at 11:57 AM, Rick Bensene <rickb at bensene.com> wrote:
>> Mr. Havermout wrote:
>>> Can someone identify this circuit board? It's some sort of magnetic core
>>> memory. I've had this for ages and I've always wondered what it is and
>>> where it comes from.
>> Whatever this was, it appears that it has been scavenged for parts over time. Many components appear to be missing.
>> It seems to me from looking at the board carefully that it could be a small wire-rope ROM, or, perhaps the cores (one module has its cover removed exposing the large ferrite rings) serve as pulse transformers for magnetic core that resides on another circuit board.
>> If it is a small wire-rope read-only memory, it appears that it could be a 16x16 ROM, perhaps hard wired for some kind of small bootstrap loader or the like.
>> It looks like there are 16 wire drivers (two of the driver transistors are missing), and 16 sense amplifiers.
> If it's a core-rope ROM, which seems plausible, then it would be 256 x 16. Core rope uses 2 select ("inhibit") lines/drivers per address bit. So 16 drivers means 8 address bits, i.e., 2^8 words.
Never mind, that was all wrong. It takes only 2*n wires to select one of 2^n cores in a core-rope ROM, so far that was correct. But the number of ROM words equals the number of cores (obviously). So if there are 16 cores that would mean 16 words, but it also means that only 8 drivers are needed (4 address bits). So there's a puzzle.
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