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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.

John Elliott 14 May 2004