Editing Amstrad PC3086 Maintenance Guide (section)

== Option links ==

The PC3086 links are on the main board (drawing on p. 11-5 of the user manual). Amstrad marks several "do not change"; Elliott worked out their functions from the service manual schematic.<ref name="g3links" /><ref name="s3lnk">John Elliott, [https://www.seasip.info/AmstradXT/pc3086lnk.html "PC3086 option links"], seasip.info, 23 January 2004. Retrieved 2026-10-02. Link functions from the user manual and the service manual schematic.</ref>

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''PC3086 option links'''
! Link !! Out (no jumper) !! In (jumper fitted)
|-
| LK1 || Drive A has changeline (720 KB) || Drive A has no changeline (360 KB)
|-
| LK2 || Drive B has changeline (720 KB) || Drive B has no changeline (360 KB)
|-
| LK3 || Power-on self test enabled || Self test skipped
|-
| LK4 || colspan="2" | Do not change; jumper on pins 2 and 3. Elliott reads pins 1 and 2 as reducing memory to 512 KB
|-
| LK5 || colspan="2" | Leave open. Elliott reads it as selecting a 32 KB BIOS ROM in place of 16 KB
|-
| LK6 || colspan="2" | Do not change; jumper on pins 1 and 2 (write precompensation 250&nbsp;ns; pins 2 and 3 give 125&nbsp;ns)
|-
| LK7 || On-board COM1 enabled || On-board COM1 disabled
|-
| LK8 || On-board VGA enabled || On-board VGA disabled
|-
| LK901, LK902 || colspan="2" | Primary display when the VGA is disabled: both out, EGA or VGA card; LK902 in, CGA 80 columns; LK901 in, CGA 40 columns; both in, MDA or Hercules
|-
| LK952 || colspan="2" | Hard disk I/O address: pins 1 and 2 primary, pins 2 and 3 secondary
|-
| LK953 || colspan="2" | Hard disk BIOS: no jumper, disabled; pins 2 and 3, primary; pins 1–2 and 3–4, secondary
|-
| LK954 || colspan="2" | Do not change (leave open)
|-
| LK955 || colspan="2" | Hard disk interrupt, from the schematic: pins 1 and 2 IRQ 5, pins 2 and 3 IRQ 2
|}
LK951 is not in Amstrad's table; Elliott links it to the IDE reset line on the schematic.<ref name="s3lnk" /> The display links LK901 and LK902 are explained on p. 6-7 of the manual.<ref name="g3video" />