# Index of /library/

Short technical notes on old PC hardware, each with the answer first, what it applies to, how it was measured, and how to check it yourself.

Source page: https://barelybooting.com/library/

Small technical notes on old hardware: the answer first, then what it applies to, how I know, and how you can check it yourself. The journal says what happened; these say what's true, and they get revised when I learn more. Every claim carries its evidence: <span class="ev ev-i">[I]</span> measured on real hardware, <span class="ev ev-e">[E]</span> in the 86Box emulator, <span class="ev ev-u">[U]</span> on a CPU model, <span class="ev ev-d">[D]</span> documented only.

## Boards and chipsets

- [PB686 "turbo": 8042 output-port bit 2 selects fast or slow](/library/pb686-turbo-8-12-mhz-8042-output-port-bit-2/)  
  Applies to: Packard Bell PB686, TI TACT82000 chipset, Intel N80286-12; bit 2 measured under Atlas 286 M14 (2026-10-12); keyboard toggle under Atlas 286 M15 (2026-10-18); MS-DOS HIMEM.SYS. Revised 2026-10-25.
- [PB686 CMOS is 64 bytes: 40h to 7Fh alias 00h to 3Fh](/library/pb686-cmos-64-bytes-40h-7fh-alias/)  
  Applies to: Packard Bell PB686, TI TACT82000 chipset; read 2026-09-02 and 2026-09-11 under the original Phoenix 3.10 BIOS with MS-DOS DEBUG scripts. Revised 2026-10-25.
- [PB686 chipset: TI TACT82301, 82302 and 82303, not Chips and Technologies](/library/pb686-chipset-ti-tact82000-not-chips-and-technologies/)  
  Applies to: Packard Bell PB686 (badge PACKMATE I, assembly 99109-913-, Made in Korea); TI TACT82000 chipset; one board, read in August and September 2026. Revised 2026-10-25.
- [PB686: there is no fast A20 on port 92h](/library/pb686-no-fast-a20-port-92h/)  
  Applies to: Packard Bell PB686, TI TACT82000 chipset; 92h tests 2026-09-12 under the original Phoenix 3.10 BIOS; D0h test 2026-10-12 under Atlas 286 M14. Revised 2026-10-25.



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