Installation manual for SIDFX

Last updated: January 8th 2018 (version 26)

It is important that you read the following instructions carefully before unpacking and installing your SIDFX unit.

Failure to do so may cause damage to SIDFX or your computer.

Please check your setup after finishing installation, run the SIDFX configuration tool and verify that your SIDs are correctly detected (see the bottom status line).

SIDs detected as unknown are operated in "safe mode" at 9V (and with 8580 filter caps) so the chips will not be damaged, but they may not operate properly for several reasons.

Lotus Electronics ApS cannot be held liable for any damage caused by incorrect installation or improper handling or use.

If the box contents feel colder than room temperature then please wait 12-24 hours before proceeding with the installation.

This allows potential condensation to evaporate, which could otherwise cause damage to your SIDFX, SID chips or computer during or after power-on.

Precautions must be observed for handling electrostatic sensitive devices. Ideally both you and your computer should be properly grounded during installation in order to efficiently protect your SIDFX, SID chips and computer against electrostatic discharges.

Unfortunately this is not easily accomplished by most end users, but using an ESD wrist-strap is highly recommended.

With ESD wrist-strap

ESD wrist-straps with integrated discharge resistor and grounding wire with alligator clip are available from e.g. eBay for as little as 1 USD including shipping.

First completely discharge yourself to a grounded metal part of your home (heating radiator, water pipe, kitchen sink, exposed metal on kitchen appliances etc.).

Then put on the wriststrap and connect the alligator clip to the exposed metal cage that surrounds your computer’s expansion port connector, but be sure not to touch any of the connector contacts.

This will effectively put you and your computer at the same potential.

Without ESD wrist-strap

Using an ESD wrist-strap is highly recommended. But if you don’t have an ESD wrist-strap available then first completely discharge yourself to a grounded metal part of your home (heating radiator, water pipe, kitchen sink, exposed metal on kitchen appliances etc.).

Then touch the expansion port metal cage with your fingers before and regularly during installation.

This will help keeping the potential difference low.

Opening computer

Before opening your computer be sure to turn it off and unplug all cables.

There are several guides on the internet on how to open your computer Google how to open a C64. Once you are inside you must locate the SID chip (see further information below). (how to locate a SID chip, which chip numbers to look for, yes most people knows)

Once inside, you might need to unscrew a metal - or tinfoil cover/shielding that was mounted in some of the models.

After opening your choosen C64/C64C/SX-64/C128/C128D model, you will have to locate three things:

  1. The SID chip (6581/8580)
  2. The CPU (6510/8500/8502 - old C64 breadbins usually have a 6510 and newer slim C64C have a 8500)
  3. The expansion port (where you put cartridges like the 1541Ultimate, Final Cartridge, MSSIAH etc.)

(Example of how the notch on a IC looks)

Please note the orientation of the SID chip before removing it from the motherboard!

Both note the notch position on SID chip and SID socket. The SID must align with the notch of the SIDFX sockets, and SIDFX must align with the SID socket!

Use a wide flat-head screwdriver and carefully squeeze it in between the SID chip and its socket. Support the SID with two fingers while you gently twist the screwdriver a bit in order to lift the SID chip a bit. Do the same from the other end, and repeat until the SID chip is out.

Only twist the screwdriver, otherwise you can cause damage.

The main idea is to keep the pins on the SID as straight as possible, so keep switching and lifting a little from each side until it releases itself from the socket on the motherboard.

Don't use strong force or rush this, the chip-pins weren't designed to handle strong force. You are dealing with 30 year old hardware/metal and you can easily bend a chip's metal pins/legs if you use to much force.

SIDFX comes with a “riser socket” (regular IC socket) pre-installed on the SIDFX pins. This lifts SIDFX by another 4mm, and allow clearing some of the components surrounding the SID socket. It also protects the SIDFX pins for accidental bending/breaking, so it’s recommended to keep the riser socket installed.

In some cases there might not be room, so the riser socket needs to be removed before installation. This is the case when SIDFX needs to fit computers with metal shielding covering the motherboard.

Removal is performed with a wide screwdriver, please see the section describing SID chip removal.

Avoid short circuit

Some models have components that can conflict in height surrounding your SID socket

Bend those components gently away/down

Don't use strong force, you are dealing with 30 year old hardware! The components weren't designed to handle strong force.

This will prevent the SIDFX unit to touch any of them and thereby getting heated or short circuited from below.

Decide which direction would fit your model the best and push slowly and gently in that direction, don't flip them back and forth, only one direction.

Make sure they don't touch any other component after bending.

Now insert the SIDs you want in your SIDFX unit.

SIDFX relies on a SID in socket 1, so if you only have one SID, please always install it in socket 1. SID1 is the default SID in some operation modes (see operating modes for more details).

If you plan on composing/playing stereo tunes with 6581+8580 you should consider installing 6581 as SID1 to allow standardizing.

You could lift it up in your hands while doing this, so you don't apply force to the pins below the SIDFX unit while applying pressure ontop the SID chips.

Once you have inserted the SIDs you want in your unit, place it over the SID socket on the motherboard. Take your time to make sure that ALL pins from the SIDFX unit are aligned with the pinholes in the SID socket.

If you are certain that all pins are alligned, then start applying gently pressure from above. Put pressure on both SIDs to balance the pressure.

Don't stress this - take your time, better safe than sorry...

What are the purpose of the 4 cables?

  • Switch #1 for manual selection
    • Left = audio from SID socket #1 only
    • Center = Auto/API controlled
    • Right = audio from SID socket #2 only
  • Switch #2 for 3 configurable profiles loaded upon reset and power-on (+ unlocking firmware update)
  • Audio cable with mini-jack for head-phones, external speakers, recording
  • Grabbers to enable stereo playback, allowing the address spaces to map the secondary SID

When installing the accessory cables please observe the connector function printed next to each connector. If used the switches and audio jack should be installed permanently by drilling a hole for each in a suitable place and screwing it in place. A switch can short-circuit the computer if left rattling around inside or outside the chassis.

In-depth explanation of the 4 cables

OUT: The audio output socket (mini-jack) provides two audio output channels. The left and right audio channels are a direct result of the active SIDFX configuration (see operating modes for more details) and the position of switch 1, which will override the audio path when not in the center position (see switch 1 control for more details). The C64 mono output is always a mix of the left and right audio channels.

SW1: Switch #1 controls the audio output. In the CENTER switch position the audio output is controlled by the active SIDFX configuration (see operating modes for more details). With the factory default settings this effectively means SID1 in the left audio channel and SID2 in the right audio channels (if two SIDs are installed). In the LEFT switch position the audio output from SID1 will be routed to both output channels. In the RIGHT switch position the audio output from SID2 will be routed to both output channels.

SW2: Switch #2 controls which default configuration profile is loaded at the time of reset or power-on. With the switch positions CENTER, LEFT, RIGHT you have up to 3 user configurable profiles. This allows you to quickly preload a specific SIDFX operating mode before loading a program, e.g. a demo or music editor (see operating modes for more details).

BUS: The grabber cable is used to capture the address lines required in order to allow mapping SID2 to an alternate address space. All 3 grabbers must be connected in order to select a stereo operating mode, which is required for stereo SID playback (see operating modes for more details).

Grabber locations

Install the mini-grabbers on the following pins inside the C64/C128:

Blue grabber: A5 signal at CPU pin 12 (IC marked 6510/8500/8502)

Green grabber: A8 signal at CPU pin 15 (IC marked 6510/8500/8502)

Yellow grabber: IO1 signal at expansion port pin 7 (7th pin from the left, when viewed from inside the computer)

It has a different location on SX-64 (picture will follow)


On models with metal shielding (seen when opening the computer) it may be more difficult to re-install the shielding while the grabbers are in place.

There are alternate locations to tap off the A5 and A8 signals that might allow easier re-fit of the shielding (please contact us for details).

In some cases the shield cannot be screwed fully down in all locations. In rare cases the metal shielding may need to be slightly modified in order to be re-installed

First you should clean the “cooling finger” that previously touched the SID, then bend it upwards so it won’t touch any of the SIDFX components (not doing so could short-circuit the SIDFX unit).

Commodore 64 (breadbin)

ASSY 250407

Use the riser socket.

ASSY 250425:

Use the riser socket.

ASSY 326298

Use the riser socket.

Commodore 64C (slim)

ASSY 250466

Remove the riser socket in order to fit below metal shield.

ASSY 250469

Remove the riser socket in order to fit below keyboard.

Commodore 128/128D

ASSY 310379

Remove the riser socket.

Commodore 128DCR

ASSY 250477

Unscrew the power supply held by 4 screws and move it to the side (note the orientation of the power connector going to the motherboard).

Unscrew the supporting standoff and replace it with a screw from another location, where you screw in the standoff for safe keeping.

Now install SIDFX, use the riser socket, and connect the grabbers to the standard locations.

Re-install the power supply, but use one of the screws to lift the power supply above its original position. Remember to re-install the power connector.

On the opposite side install the self-adhesive rubber bumper (included with the extended length cable kit) underneath the power supply so it is supported by the VIC/VDC metal cage on the motherboard.

Commodore SX-64

ASSY 251102

Use the riser socket.

Bend down all the components close to the SID socket but avoid causing shorts between them.

Connect the blue and green grabbers to the standard locations, and connect the yellow grabber to UC1 pin 10 (IC marked 74LS139).

C64 Reloaded MK1 (by Individual Computers GmbH)

C64 Reloaded must be jumped for “6581” operation before installing SIDFX. Please refer to the C64 Reloaded manual for the required jumper changes.

If you use C64 Reloaded with a C64C chassis then please use our custom SIDFX adapter for Reloaded MK1 which is included with SIDFX-R1 and available separately as an accessory upon request.

C64 Reloaded MK2 (by Individual Computers GmbH)

Coming soon...

The riser socket from SIDFX must be moved to the pins of the adapter in order to lift it above the ZIF socket.

Removal is performed with a wide screwdriver, please see the section describing SID chip removal.

Install the self-adhesive rubber bumper on the component marked “151” in the center of the SIDFX module. This will ensure clearance between SIDFX and the C64 Reloaded motherboard.

Post installation test

After finishing the hardware installation please check your setup by downloading and running the SIDFX configuration tool.

Please verify that your SIDs are correctly detected (see the bottom status line). SIDFX should always detect your SIDs as either 6581 or 8580 (or NONE if no SID is installed). SIDs detected as unknown (UNKN) are operated in "safe mode" at 9V (and with 8580 filter caps) so the chips will not be damaged, but they may not operate properly for several reasons. Please contact us in case you experience that SIDs are being incorrectly detected.

Please verify the function and orientation of the two switches. The bottom status line shows you the live position of switch #1. Switch #2's position is indicated by config column on the screen that is highlighted.

The bottom status line also show whether your SIDFX is stereo capable or not “SC=Y” for yes or “SC=N” for no. For stereo capability two SIDs must be (correctly) detected and all 3 grabber cables must be installed in the correct locations.