Old RPN w/ discrete components and acoustic memory

[ndzied1]

Maybe it’s been shown before but really cool video.

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

[Jaco@cocoon-creations.com]

(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.

[toml_12953]

(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?

[Jaco@cocoon-creations.com]

(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

[cruff]

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.

[toml_12953]

(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?

[Dave Britten]

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.)

[Paul Berger (Canada)]

(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.