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Old RPN w/ discrete components and acoustic memory
03-04-2020, 01:13 PM
Post: #1
Old RPN w/ discrete components and acoustic memory
Maybe it’s been shown before but really cool video.

https://youtu.be/2BIx2x-Q2fE
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03-05-2020, 05:41 AM
Post: #2
RE: Old RPN w/ discrete components and acoustic memory
(03-04-2020 01:13 PM)ndzied1 Wrote:  Maybe it’s been shown before but really cool video.

https://youtu.be/2BIx2x-Q2fE

Amazing. Great find! Thoroughly enjoyed it.

Jaco Mostert, Elec Eng
42S, DM42, WP34C/S, 28C, 35S, 32Sii, owned 11C; used 67, 85; iOS: 42s, Free42, WP31S/34S, HCalc; OSX: WP34C.
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03-05-2020, 05:44 AM
Post: #3
RE: Old RPN w/ discrete components and acoustic memory
(03-04-2020 01:13 PM)ndzied1 Wrote:  Maybe it’s been shown before but really cool video.

https://youtu.be/2BIx2x-Q2fE

I still don't really get acoustic memory. How does it store the information for more than a few milliseconds as the pulse goes around the loop to the end?

Tom L
...other than that, Mrs. Lincoln, what did you think of the play?
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03-05-2020, 06:12 AM
Post: #4
RE: Old RPN w/ discrete components and acoustic memory
(03-05-2020 05:44 AM)toml_12953 Wrote:  
(03-04-2020 01:13 PM)ndzied1 Wrote:  Maybe it’s been shown before but really cool video.

https://youtu.be/2BIx2x-Q2fE

I still don't really get acoustic memory. How does it store the information for more than a few milliseconds as the pulse goes around the loop to the end?

The way I understand it, is that it gets sent around again once picked up by the sensor on the end. This video attempts to show both ends:

https://youtu.be/N9cUbYII5RY

Jaco Mostert, Elec Eng
42S, DM42, WP34C/S, 28C, 35S, 32Sii, owned 11C; used 67, 85; iOS: 42s, Free42, WP31S/34S, HCalc; OSX: WP34C.
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03-06-2020, 01:50 AM
Post: #5
RE: Old RPN w/ discrete components and acoustic memory
If you've ever read a description of how the magnetic bubble memory operated, the design is similar in that the contents of the loop need to be regenerated continuously. At the point (in time) there a specific data bit falls off the end is where you read the value or write a new value.
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03-06-2020, 02:04 PM
Post: #6
RE: Old RPN w/ discrete components and acoustic memory
(03-06-2020 01:50 AM)cruff Wrote:  If you've ever read a description of how the magnetic bubble memory operated, the design is similar in that the contents of the loop need to be regenerated continuously. At the point (in time) there a specific data bit falls off the end is where you read the value or write a new value.

So that's what the fan is for? To blow all of those bits that fell off the end out of the machine? Big Grin

Tom L
...other than that, Mrs. Lincoln, what did you think of the play?
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03-09-2020, 01:04 PM
Post: #7
RE: Old RPN w/ discrete components and acoustic memory
The funny thing is that the program memory in the HP 65 is very conceptually similar, except that it's a very long shift register rather than a mechanical/acoustic device. Technically, the 65 doesn't have "RAM" in that regard, since it isn't "random access", and there are no absolute addresses. It just reads/inserts/swaps bits as they pass by the window. (I imagine there's a bit more to it to allow the calculator to do things like inserting and swapping steps for moving the program pointers around, but that's the general idea.)
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03-09-2020, 02:41 PM
Post: #8
RE: Old RPN w/ discrete components and acoustic memory
(03-05-2020 05:44 AM)toml_12953 Wrote:  
(03-04-2020 01:13 PM)ndzied1 Wrote:  Maybe it’s been shown before but really cool video.

https://youtu.be/2BIx2x-Q2fE

I still don't really get acoustic memory. How does it store the information for more than a few milliseconds as the pulse goes around the loop to the end?

Many years ago I used to service a proof machine that had delay line memory and that machine had a solid state shift register in between the two ends of the delay line that you would insert and retrieve data from, but since it is a continuous stream of bits that you cannot stop, you need to know when a unit of data is aligned in the solid state register and insert or retrieve data before the shift register advances.

I also took a call on a test scoring machine one time that used delay line memory to hold the correct answers that where compared to the students answer sheets.

Paul.
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