WD1002-WX2

This is hard disk controller, made by Western Digital, intended for XT-class computers.

The WD1002-WX2 must not be confused with the WD1002S-WX2, a different controller.

The document at here contains a single reference, indicating an introduction year of 1983.

In the examples of this card that I have heard of, the BIOS ROM has been customised - Western Digital produced a customised ROM for a computer maker.  Specifically, the customisation is the hard drive table within the BIOS.  The implication of this is that, if you acquire one of these cards, the drive table shown in Internet sourced documention, may not match your card's drive table.


E17/E18 jumper

Fitted to all cards.  Located in the top-left corner of the card.  Blue appears to be the standard colour.

We know from page 2-2 of the Compaq Deskpro document at here, that the E17/E18 jumper must not be removed.  This will be a 'factory use only' type jumper, similar to what is found on a lot of other models of Western Digital controller of the time.


Hard drive support

The BIOS ROM on the card supports up to four different drive geometries (geometry = cylinder/head/sector counts).
Those geometries are located in a drive table within the ROM.  An example (repeat: example) is here.
That example also shows you how to use SpeedStor software to determine the contents of the drive table in your card's ROM.


Hard drive selection

Which of the four drive geometries is selected ?

Page 2-2 of the Compaq Deskpro document at here indicates that the WD1002-WX2 that Compaq used had a 4-switch switch block, designated SW1, fitted.
Looking on the card for a location where a 4-switch switch block could fit, there is only one location; to the right of the ROM. (photo)
So, what I suspect (repeat: suspect) is that Compaq fitted a 4-switch switch block, after cutting the following four traces:
* Trace between E5 and E6
* Trace between E7 and E8
* Trace between E9 and E10
* Trace between E11 and E12

If my hypothesis is correct, then because of the above four traces, cards without a switch block are effectively set to the drive geometry that would have been selected had a switch block been in place, and all of the switches in that block been turned on. According to the information here (a post by nollkolltroll), that corresponds to the fourth entry in the drive table.

Note that the SW1 settings in the Compaq Deskpro document apply to the WD1002-WX2 that Compaq used in the Deskpro. If your WD1002-WX2 is from a different computer, then the drive table in your WD1002-WX2's ROM is probably different (i.e. the SW1 settings do not apply to your card).


Some photos

Example 1
Example 2
Example 3
Example 4
Example 5    (supplied as part of the 'Qubie PC10: Hard-Disk Subsystem')