(Image credit: Klaus Scheffler on www.4004.com)

A sneak preview of a complete MCS-4 computer, built from discrete transistors, has been shown off to mark the recent Intel 4004 anniversary. In the picture below, you can see the calculator interface flanked by seven hand-wired ‘chips’ that implement the entire original Busicom 141-PF calculator logic in hardware. That means those framed PCBs you see are supersized remakes of the Intel 4004 CPU (the largest at center), plus 4001 ROM, 4002 RAM modules, and 4003 shift registers.

Center bottom: 4004 CPU. Center top: 4001 ROM. Upper left: Three 4003 shift registers. Right: Two 4002 RAMs. Lower left: Interactive Busicom 141-PF calculator user-interface replica. (Image credit: Klaus Scheffler on www.4004.com)

The pictured supersized calculator, recently completed by Klaus Scheffler and Lajos Kintli, is set to go on exhibition at the Enter Museum in Switzerland sometime next year. It will be an interactive exhibit, with flowcharts and register valuations, as well as the physical calculator keypad being available to prod, we assume.

This fascinating project began several years ago, with the development team starting with the CPU at its heart – the legendary 4-bit Intel 4004. Remember, Intel designed this ‘first commercial microprocessor’ specifically for the Busicom calculator, which came out in 1971. So, it is apt that the whole Intel 4000 family has now been remade for posterity, to support a working supersized calculator.

Tim McNerney, the project lead behind the Intel 4004 50th Anniversary initiative, explains that he visited Intel in July 2005 to obtain access to the three large engineering drawings of the 4004 preserved in the company archives. Federico Faggin (the original 4004 chip designer) and Rachel Stewart were there to confirm these were the complete set of drawings, “drawn just like the chip layout.” Eventually, this research led to the first of the 130x scale discrete transistor ‘chips’ you see in the main image.

Interestingly, the far larger 4004 CPU runs around twice as fast as the vintage silicon, at up to 1.5 MHz vs the original 740KHz. The museum blog credits “Scheffler's original choice of low-capacitance, 4-terminal FETs designed for RF applications... and many hours of hard work,” for this improved performance.

To remake super-sized working versions of the 4001 ROM, 4002 RAM modules, and 4003 shift registers required further digital archeology. And now we have this glorious exhibit ready for the public (on show from next year).

We also recently reported on what was the ‘real’ world’s first microprocessor, the MP944. That particular innovation was deployed by the U.S. military over a year before the Intel 4004 was commercially available. However, the more capable MP944 microprocessor remained classified until 1989.

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