A typical [] HDC card

That stands for "Hard Drive Controller" -- this one includes a FDC (Floppy Drive Controller), two COM (serial) ports, a GAME port, and a Printer (parallel) port.

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The connector strip at the bottom indicate that this is a 16 bit (ISA) card.

Near the bottom of the card are 8 sets of two jumpers.

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But it could be otherwise. You really need the "docs" when things get strange. See the notes below.

Below that is a three pin set which selects the IRQ for the parallel port, shown as 2-3 jumpered.

1 [] 3

When in doubt, the lines on the card can often be traced. The lower IRQ lines connect on the solder side of the card, on the first (8bit) section of the card. Counting contacts from the screw-down end of the card (the rear of the computer), the IRQ lines are found as follows

The IRQ lines normally used for the printer are easy to follow. they lead directly to pin 1 and pin 3 of the above 3-pin jumper block. But IRQ lines for the COM ports are often difficult to follow.

The higher IRQ lines come in on the 16 bit extension part, also at the solder side of the card. Counting, again, from the screw-down end of this section, the IRQ lines are...

IRQ 13 is missing because it is used by the FPU, and not by any card.

Inspecting the back of the card reveals (in this instance) that only IRQ line 14 is brought in. We could assume that the HDC uses it, and that there will be no other choice.

At the top, behind the exterior COM port are a set of 8 3-pin jumpers. The board is marked "DIS/EN" above the jumper block. Assume this means "disable", "enable."


The board is marked, below the jumper block:

This is only 4 indications, but there are 8 jumpers. The solution is to try some of the following assumptions..

A few trial and error attemps will probably reveal what is what.

If you really get stuck, get on the internet and look up the manufacturer, or check out card jumper sources at some of the FTP sites like UIArchive, Garbo, or Simtel.

HOST: Outflux.net, http://www.Outflux.net
URL: http://jnocook.net/user/hdc.htm