Burroughs LSIC B Series Gate Array (AMI 1845 9909)  
Written by AnubisTTP on 2022-10-02  



These largely undocumented parts, produced by AMI, Fairchild, and Burroughs, are LSIC gate arrays used almost exclusively in Burroughs B series minicomputer systems. Burroughs B series computers were bulky console-style machines which were typically built into a desk or table with a large line printer as the only form of display. The AMI 1845-9909, shown in the thumbnail, is believed to be a 150 element gate array originally manufactured for use in a Burroughs B80. Nine of these gate arrays would be combined to form the complete 8 bit central processing unit of the B80. Unfortunately the exact specifications of these chips is unknown; no datasheets or part lists appear to have been released by Burroughs, and the homebrew electronics community has made little progress in unlocking their secrets. Despite this, Burroughs processor chips see a decent amount of turnover amongst chip collectors, due almost entirely to their strange form factor. Burroughs gate arrays are packaged in large white ceramic pin grid carriers with gold traces and a central round cavity lid, and have a distinct appearance unlike any other integrated circuit. Electronics lore has that the original Burroughs service technicians referred to these devices as 'fried egg chips' due to their unusual packaging. The example shown in the thumbnail was manufactured in 1976.


Burroughs AMI 1845 9909 Integrated Circuit
Burroughs Gate Array integrated circuit at rest. This particular example was produced by AMI.

Burroughs Gate Array Processor
Burroughs B series gate arrays are one of only a handful of integrated circuits produced in a white ceramic pin grid array package.

AMI White Ceramic Processor
The silicon age.

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