You should follow these instructions if you already have an XM1541 multitask cable and you want to transform it.
Because you will solder a cable onto some pins of the VIA#1 chip inside the drive, you will have to first make sure that these pins are not used for any other purpose. This depends on the version of the drive you have:
In original Commodore 1541 drives, nothing is defined to any of the bits of Port A. You can solder the cable without any problem.
In 1541C drives, bit 0 of Port A is used for the detection of the head being over track 1. After stripping this connection off of the chip, you will have to replace the DOS ROM with that of the 1541 or the 1541-II. Otherwise you'll get strange results when the drive is seeking: the DOS tries to rely on the detector line which doesn't exist anymore.
In 1541-II drives, bit 0 of Port A is grounded, strip this connection off of the chip.
On circuit diagrams, plugs are displayed as viewed from the back side, the solder side. Chips are displayed as viewed from above; also, see the small semicircular cut for finding the correct orientation. When in doubt, see the corresponding description on the legend page.
First, create the parallel port for 1541 drives or the parallel port for 1570 and 1571 drives.
You need the following parts to build this cable:
One solderable 15-pin male plug (PC game plug)
A shielded or unshielded 8-wire cable of, preferably, at most 2 meters
Step 1. Solder one end of the cable onto the game plug.
Step 2. Solder the other end of the cable onto the parallel plug. You should have the following connections:
|Game plug|| Parallel plug |
|1|| 2, Data 0 |
|2|| 3, Data 1 |
|3|| 4, Data 2 |
|4|| 5, Data 3 |
|5|| 6, Data 4 |
|6|| 7, Data 5 |
|7|| 8, Data 6 |
|8|| 9, Data 7 |
|not connected||18-25, GND |
The original connections of the XM1541 multitask cable are shown in grey. You can find the description of all parts used on the diagrams at the legend page.
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