Field access bubble-to-bubble logic operations

Bubble-to-bubble logic operations can greatly enhance the versatility of bubble memory devices. Our experience to date, however, has shown us that logic operations reduce the device operating margins to a degree that would allow logic only where the ratio of memory sites to logic gates is greater than one hundred. For example, quasistatic rotating field operation of exclusive OR, AND/OR, and replicate gates was obtained for a ± 3.5 percent bias margin at 45 to 55 Oe rotating field drive for an AND/OR gate to a ± 1.5 percent bias field margin at 50 to 60 Oe rotating field drive for an exclusive OR gate. In all cases these devices were prepared by ion milling or chemical etching T-bar, Y-bar, or chevron patterns in 3000 to 5000 Å thick Permalloy films on glass. The pattern feature sizes ranged from 3 to 7.5 μm. The Permalloy on glass patterns were placed on epitaxially grown magnetic garnet wafers with bubble diameters ranging from 8 to 17 μm. Circuit operation was determined by visual observation. In all cases, the results are from either the first design of the circuits or the first iteration design.