Bubble memory devices

Scanning steven.alan.canning at verizon.net
Mon Feb 18 16:13:35 CST 2008

> Hi,
> Whilst waiting for a video to download (I'm still on dial-up) I decided to
have a flick through an issue of 80 Microcomputing. It's issue 10 (October
1980) and inlcudes an article about the row about whether the US government
and/or patent office should honour copyrights for computer software.
> Anyway, on page 46 I stumbled across an interesting article (called "A
Slow Road To Bubble Memories") about bubble memory. The main bubble memory
manufacturers of the time were Intel Corp., Texas Instruments and Rockwell
Int. The article also mentions that Rockwell had a bubble system, a 256K bit
board, available for $1,800. Meanwhile Intel had a bubble system in kit
form - 7110-1 Magnetic Memory board came with all control and support
circuitry - and sold for $2,000.
> What happened to bubble memory? Did it die out due to the costs, or did
people prefer to use cassettes, disks etc. instead?
> Regards,
> Andrew B
> aliensrcooluk at yahoo.co.uk

Around 1978 ish in the R&D section of Odetics Spacebourne we were looking at
bubble memory for use in satellite / shuttle applications ( I think it was
either the Intel or IBM 256K unit). They are kinda weird to use. To move the
bubbles ( in the loops ) requires an excitation by 90 degree phase shifted
triangular current waveforms ( Tony would dig that ). The unit had two sets
of 80 minor loops and two major loops. To read ( a destructive read, more on
this later ) requires that you transfer bits ( bubbles ) from a minor loop
( where it resides ) into a major loop to be read. To read a bit, it enters
an annihilator / replicator where it is read ( destroyed ) and then
replicated back into the major loop. As with most devices, the yield of the
device is never 100% so there is a " loop map " that tells the controller
which minor loops are bad and should be avoided ( kinda like a hard drive
does with bad sectors ). Extra loops are built-in to accommodate the bad

We didn't use bubble memory because it doesn't like cold ( likes to run
around 30 to 40 degrees C ), it's relatively heavy for it's capacity, it's a
power hog and bad things happen when you are doing a read and the power is

The plus side is it doesn't mind radiation ( much ); it draws zero power
when shut down and is non-volatile. But then, so is battery-backed up
rad-hard RCA CMOS memory ( Silicon-On-Sapphire ) ....

I sold a GRID computer for about $200 that had 384 Kbytes of bubble memory.

Best regards, Steven

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