On Fri, Sep 1, 2023 at 10:53 AM Rick Bensene via cctalk < cctalk@classiccmp.org> wrote:
> He also developed a very interesting calculator, based somewhat on the > principles of the LGP-30 computer for Diehl in West Germany. The machine > was fully transistorized and used only 142 transistors in its logic. It > was based on magnetostrictive delay lines (two of them), and was a fully > microcoded architecture, I believe the first electronic calculator to be > completely microcoded. > > Since read-only memory (for the microcode) was either physically very > large, or complex and expensive to build at the time (diode ROM, wire rope > ROM), the microcode was loaded into the calculator at power-up time from a > two channel punched metal tape. One channel provided the clocking, and > the other channel provided the bits. > > It took just under a minute from when the calculator was powered on until > the microcode was loaded into a delay line, and from there, all operations > of the machine were controlled by the microcode in the delay line. > > The machine was able to be implemented with so few transistors because the > microcode word was quite wide, and was designed so that it was sequentially > interpreted as the bits streamed out of the delay line, so not all that > many flip flops were needed. Working registers were stored in the other > delay line, along with program steps (yes, the machine was programmable). > > The design was very elegant. The machine debuted as the Diehl > Combitron, and the cool thing about its design was that it was really easy > to augment by just changing the microcode tape (which was quite easily > done...bugfixes could be easly installed even by end-users, though such was > discouraged). > > Soon after the Combitron was introduced, an augmented version was > introduced called the Combitron-S that added a small amount of I/O > circuitry and additional microcode to implement operations to allow the > addition of an external punched paper tape reader/punch. > That is just the coolest. Basically a desk-sized LGP-30-alike. Thanks for that history, Rick. Sellam
