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The Raspberry Pi 4 is a beast amongst single board computer systems, with a quad core Cortex-A72 processor operating at 1.5 GHz, and as much as 8 GB of RAM. However even nonetheless, many people run into conditions the place we merely want extra energy than is on the market. Engineer Robin Grosset has apparently felt this ache personally, so he constructed a Raspberry Pi HAT with a coprocessor that may give the board that further oomph wanted to tear by the extra demanding duties that you just throw at it.
For clarification, once I say demanding duties, by that I imply duties that aren’t in any respect demanding — not even barely. That’s as a result of the processor Grosset has added to the Raspberry Pi is the Intel 8086, which was first launched approach again in 1978. It’s definitely not a modern-day powerhouse, however it’s practically equivalent to the much-loved 8088 processor discovered within the very first IBM Private Pc, and likewise was the primary chip to implement the x86 instruction set structure that’s nonetheless in heavy use at the moment.
Intel 8086 CPU (📷: Thomas Nguyen)
Like many different processors of the period, the 8086 PDIP package deal has pins for the processor to specify tackle places that it must both learn from or write to, and varied different management traces. Information is transferred between the processor and different peripherals (e.g.: RAM, ROM, audio/video chips) through a 16 bit broad information bus. By supplying the clock sign with a GPIO pin on the Raspberry Pi, one can then learn the values on the tackle bus, and interpret them within the context of the state of the opposite management pin values to find out what state the CPU is in. It’s then doable to place an applicable sign on the info traces (or learn from them) by the Raspberry Pi GPIO pins to simulate peripheral gadgets. On this approach, Grosset was capable of ship the 8086 program directions, and likewise simulate an exterior RAM chip.
The HAT was demonstrated operating MS-DOS Model 6.22 by a customized terminal software operating on the Raspberry Pi. It’s not precisely quick, with the working pace estimated at roughly 0.3 MHz, which can be a considerably beneficiant estimate given the gradual pace at which a listing itemizing prints within the demonstration video. Extra retro enjoyable could also be accessible sooner or later, with a CGA/VGA graphics emulator within the works for the HAT. If that challenge involves fruition, will probably be doable to fireplace up Zork or Defender, operating on unique {hardware}, albeit very slowly — the 8086 was usually clocked between 5 and 16 MHz in computer systems of the period.
Grosset has made his work accessible on Github below the GPL 3.0 license, so be sure you test it out if you are interested in retro computing or pc engineering. 8086 CPUs, and pin-compatible processors just like the NEC V30, can nonetheless be bought pretty inexpensively from on-line retailers and public sale websites in case you would not have one in your elements bin already.
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