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PDP-10 Emulation
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@jeffpar jeffpar released this 01 Mar 17:29
· 2185 commits to master since this release
v1.34.1
305f8bc

This release introduces another PCjs emulator: PDPjs for the PDP-10.

Although I'd like to say that the PDP-10 emulator builds on my recent experience writing a PDP-11 emulator, the architectures are actually quite different. Although the PDP-10 (1968) was released only a couple of years before the PDP-11 (1970), the PDP-10 is really just an extension of the PDP-6's 36-bit architecture, which was designed in 1963 and released in 1964.

And a number of conventions we've come to expect today weren't conventions in the early 1960's. For example, DEC numbers the bits of their 36-bit words from left-to-right, with bit 0 being the most significant bit and bit 35 the least significant. Another oddity: 36-bit multiplication produces 72-bit results, but they contain only 70 bits of magnitude with 2 matching sign bits -- a format that was presumably more convenient for the hardware designers.

I'm sure I'll discover more oddities over time, because the PDP-10 emulator is far from complete. At this point, the only instructions it supports are "Half Word" move instructions, along with all their many variations. The built-in debugger is where I've invested most of my efforts so far, which includes a fully functional disassembler and assembler.

More details can be found in the PCjs Blog.

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