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. 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. people prefer to use cassettes, disks etc. instead? 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 loops. 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 disrupted. 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