B5000 instruction set

<p>The Burroughs B5000 was the first <a href="/facts/Stack_machine/IBtk4NRA">stack machine</a> and also the first computer with a <a href="/facts/Memory_segmentation/QCUGw5v5">segmented</a> <a href="/facts/Virtual_memory/Lw2GemF5">virtual memory</a>.
The Burroughs B5000 instruction set includes the set of valid operations for the B5000, B5500 and B5700. It is not compatible with the B6500, B7500, B8500 or their successors.
</p><p>Instruction streams on a B5000 contain 12-bit <a href="/facts/Syllables/Ylt7pyJe">syllables</a>, four to a word. The architecture has two modes, Word Mode and Character Mode, and each has a separate repertoire of syllables. A processor may be either Control State or Normal State, and certain syllables are only permissible in Control State. The architecture does not provide for addressing registers or storage directly; all references are through the 1024 word Program Reference Table (PRT), current code segment, marked locations within the stack or to the A and B registers holding the top two locations on the stack. Burroughs numbers bits in a syllable from 0 (high bit) to 11 (low bit) and in a word from 0 (high bit) to 47 (low bit).
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B5000 instruction set open-in-new

B5000 instruction set