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2019-02-15 17:45:17, In: Retrocomputing
In PC casings a typical problem happens with LED display configuration. Configured to "HI/LO", it may be needed to change it, and jumpers are not always well laballed. There are many configurations. A simple one has two rows for two digits and one small row for hundreds. In this configuration, jumper settings are quite simple: You specify "turbo" configuration by placing jumpers across the row, and "normal" along the row. This way it is possible to set any value. Another type, with two digits, contains two rows of three and a logic chip. I found six revisions of these, all with different settings. What is important in this display it is needed to have Turbo connected some way to make it display at all. In some versions bottom row is for Turbo, while top for non-turbo, in other the middle row can be configured by horisontally aligning their jumpers, while Turbo required to put jumpers above and below. Some PCBs allow to be mounted inverted, so even if there's more than 199MHz, you can reverse it and have e.g. 451MHz. Quite common type for Taiwanese casings has "ONES/TENS/HUNDREDS" descriptions of jumper blocks and I think these two images will help:
They are from Enter magazine from around 1995.