PC2086 Option links

The PC2086 motherboard has several option links. I only have the service manual so the meanings of these links contain a certain degree of guesswork.

LK1-3: diagnostic mode

If all three links are connected, the computer will skip most of the self- test. This is intended for diagnosing errors. Note that unlike the earlier models, the BIOS does not support multiple languages; so these links do not have a 'language select' function.

LK4: Memory size

This is normally on pins 2 and 3. Moving it to pins 1 and 2 reduces the memory to 512k, as on earlier XTs.

LK5: BIOS ROM size

As on the PC1512, this controls BIOS ROM size. If it is connected, the ROM is treated as 32k (2x16k) rather than 16k (2x8k).

LK6: Write precompensation?

The service manual describes this as 'write precompensation cuttable option trace'. If pins 1 and 2 are connected it means 250ns; if pins 2 and 3 are connected it means 125ns.