Entering the dark mode on the C64

Dark theme for applications and operating systems is one of the most requested features over the past time. Both Apple and Google made a dark theme an essential part of user interface/UI. Dark theme reduces luminance and provides safety in dark environments, typically suitable the retro man cave. Interestingly enough the color scheme was already very popular in the 60’s as the monochrome display was flashing its characters in green or amber.

The first monitor which i got for my C64 was a monochrome green CRT (i think it was a Thomson VM3101G\Commodore 1201) and the green glow of the display has made a massive burn-in impression on my heart.

Not much later my C64 and 1541 got upgraded by installing DolphinDOS 2.0. The DolphinDOS kernel (or as Robert Russell misspelling: kernal) sported the ‘green on black’ color scheme.

The memory area where the kernal resides is $E000 – $FFFF. This ROM needs to be dumped or downloaded as a file prior to the modification. Altering the kernal isn’t much of a deal if you know how to handle a hex editor, such as HxD by Maël Hörz. Just load the kernal file and change the following values at the correct offset while using the hex editor.

Now you can use the new kernal either by configuring it in your favourite emulator/FPGA board or for the real hardware fanatics; burn the image in an (E)EPROM.

ColorOffsetDefault value

As a reference the color scheme from C64-wiki.com

ColorHex valueAppearance
Violet / purple#$04█████
Light red#$0A█████
Dark grey / Grey 1#$0B█████
Grey / Grey 2#$0C█████
Light green#$0D█████
Light blue#$0E█████
Light grey\ Grey 3#$0F█████
C64 color scheme by https://www.c64-wiki.com/wiki/Color

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Replacing the 1541-II / 1571-II/ 1581 drive power supply

Having drives without a working PSU doesn’t make sense. So this years #DiskDumpingDecember (on twitter) went a little haywire, although I did dump some EPROM to .bin files using an eprommer.

First I sourced a replacement PSU, which handles at least 12Vdc/0.5A and 5Vdc/1A, from our local recycling site. I ended up buying a TRSF, model TR-05HHD, power supply which is able to deliver 12Vdc/1.5A and 5Vdc/2A.


Now this power supply sports a 6 pin mini DIN  male connector and the 1541-II/1571-II/1581 are equipped with a 4 pin regular size DIN female connector. So this is an very easy job. Just replace the plug!

The output pin out is noted on the power supply so figuring out the pin configuration on the drive shouldn’t be a drag. Using i multimeter i figured that the internal cabling uses the industry standard.

Browsing famous FTP site Zimmers.net i found the following diagram:

drive_power_supplyNow it’s just a matter of soldering the corresponding wires to the plug.

  • Yellow – 5Vdc -> pin 1 on the drive plug
  • Black – ground -> pin 2 on the drive plug
  • Red – 12Vdc -> pin 4 on the drive plug

Posted in 1541-II, 1571-II, 1581, Hardware | Tagged , | 2 Comments

Installing µIEC in a SX-64

Wanting massive storage and a minimum of soldering in your good old Commodore SX-64? I just found the solution by using the UIEC 3.2 without the daughterboard (article: UIEC-SD-BA) supplied by Jim Brain / Retro Innovations!


I made a little dual IEC connector to plug in between the internal drive and the controller board allowing you to add a secondaty internal IEC driver. The µIEC only emulates the IEC protocol so it’s not a real 1541 replacement and does not allow fast loader and most common trackloaders (which sends a binary to the drive’s memory and cpu) to function properly. If you need full 1541 emulation i would recommend the 1541 Ultimate 2 cartridge.

So this is what i have done to accomplish the additional drive space;

The only pin which needs to be soldered to the expansion board is pin 2 on the user port. This is the 5V feed for the protocol emulating uIEC card (see SX-64 schematic diagram)


Next thing is to make a dual IEC board. This was very simple, just a 6-pin female and two 6-pin male pin headers soldered to a little PCB.



Now when this is done just plug it in to the header P11 of the I/O board (see page 13 of the schematics) and connect the other wires accordingly. To figure out the pin assignment for the µIEC i used the following scheme:

P11 I/O ------------------- µIEC
pin 1 -------- SQR -------- pin 4
pin 2 -------- GND -------- pin 1
pin 3 -------- ATN -------- pin 7
pin 4 -------- CLK -------- pin 5
pin 5 -------- DATA ------- pin 6
pin 6 -------- RESET ------ pin 3

User port ----------------- µIEC
pin 2 -------- 5 volt ----- pin 2

If you like you can peek here for some hints.



Now the internal drive, number 8, and the SD card is accessible via drive 10 (default setting of the µIEC).

As this SX-64 already been modified (to sport a Teletron 1200 modem internally) the storage bay was already altered. I decided to use double-sided sticky-tape to mount the µIEC to the right upper side of the storage bay.


Everything worked out just fine even at first start up!

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