A similar ROM was used in Wang Laboratories' 700-series calculators (as well as later 500 and 600-series) as the microcode store. Also, quite a bit earlier, another electronic calculator, the Wanderer Werke Conti calculator (designed by Nixdorf) used a wire rope ROM as a microsequencer store. Rick Bensene The Old Calculator Museum http://oldcalculatormuseum.com -----Original Message----- From: Eric Smith [spacewar at gmail.com] Received: Friday, 25 Jul 2014, 10:45AM To: General Discussion: On-Topic and Off-Topic Posts [cctalk at classiccmp.org] Subject: Re: microcode store (was Re: Looking to get into a Mini Computer...) On Fri, Jul 25, 2014 at 6:04 AM, Michael Thompson <michael.99.thompson at gmail.com> wrote: DEC also made that available as one of the building blocks of the PDP-16 family. The technology is commonly known as "core rope memory" or "wire braid memory". It is also used for the control store of the Apollo Guidance Computer (AGC) and one level of the control store of the HP-9100 desktop programmable calculator (the other level being an inductively-coupled PC board memory). It can be viewed as a smaller-scale, simplified version of IBM Transformer Read-Only Store (TROS), as used in the System/360 Models 20 and 40 and the 2841 DASD (disk) control unit. TROS was designed for better manufacturability.