https://opensource.microsoft.com/blog/2026/04/28/continuing-...
The STORE bug discovery is equally interesting from a software archaeology perspective. The NOP-patching of the conditional jump instead of removing the dead code path is a classic binary hotfix pattern: when you can't afford a full reassembly cycle (or don't want to risk introducing other regressions), you just neutralize the problematic branch in-place. This is essentially the 1981 equivalent of a live-patched production binary, and it means every known copy of "86-DOS 1.00" was actually running 1.01 logic for file sizes above 64K.
The ROL vs RCL assembler bug writeup is a beautiful bitwise brain-teaser. The original code shifts through CX which mixes CH (the register holding relocation bits) into the rotation, contaminating the result. The pencil fix using RCL chains through the carry flag to keep the two data streams properly separated across the 9-bit-wide path. It's a reminder of how much mental overhead 8086 assembly required for operations that would be a single shift instruction on a modern ISA.
(Maybe he meant the model, rather than the exact serial number? But he was in the PNW, and I understand had been very involved in the early microcomputer scene there, so I wouldn't be surprised.)
He was actively using it when he said this, so it still worked at the time.
If he still has it, some company that built an empire atop DOS should find some money in the sofa cushions, and make him an offer.