The semi analog SID chip (Sound Interface Device) is an electronic music synthesizer and its distinctive sounds are easily recognized by any Commodore 64 owner. Back in the days, most SID tunes ended up in games or demos to basically support the graphics on the screen. As many music composers love the characteristic timbre produced by the SID chip, new music is still being made for the Commodore 64 music and demo scene. In this context, the High Voltage SID Collection (link), a hobby project which organizes C64 music for both musicians and fans alike, currently has more than 48.000 SID files in their archives including the old tunes as well as newly produced music. Downloading the SID music collection is free and the vast amount of music can easily be played on modern computers using a Commodore 64 emulator and a SID player. However, nothing beats the sound of an original Commodore 64 SID chip residing in an original machine and played on an old fashioned CRT TV or a stereo sound system!
Whenever playing SID music files (a.k.a. SID’s), it quickly becomes apparent that the tunes sound differently depending on the SID chip version they were created on – the 6581 or the 8580. The former can be found in the older C64 long boards (e.g. Assy 250425 & 250407), while the latter version can be found in the newer short boards (e.g. Assy 250469). Even though both chip versions were produced by Commodore (MOS Technology or CSG) they each have a distinct sound. This means that music composed using one chip may sound differently when being played on the other chip version. These differences are intimately connected to various differences between the chips including the waveform generators, the filters and the separation between the analog and the digital circuits. As each SID chip version runs on different voltages, they cannot be swapped without some sort of hardware modification. At least not until a few days ago when I recieved this newly produced piece of hardware known as the SIDFX (link)!
The SIDFX is i dual SID chip solution which makes swapping between SID chip versions extremely easy. Mounting one of each SID chip version in the device, flicking a toggle switch will automatically switch between the 6581 and the 8580 chips. It really doesn’t get any easier than that! And there is no need for soldering either. It even plays the few stereo SID’s in the High Voltage SID Collection using both chips at the same time (for this option it is recommended to install the same chip version). Unfortunately, only one batch of 400 pieces were made and the pre-order list was filled rather quickly. So I guess I got lucky 🙂
The SIDFX Board:
The SIDFX comes with two precision sockets for installing the SID chips of your choice. The four beige sockets at the edge of the board is for connecting cables for two 3-point toggle switches, a 3.5 mm mini jack with a line level signal and a cable with grabbers to allow stereo addressing.
At the bottom of the board is a male precision socket for easy installation in any Commdore 64, regardless of the motherboard version (long board, short board, C64 Reloaded).
The SIDFX comes with a riser socket to increase the distance from the other components on the C64 motherboard, hereby mimimizing the risk of breaking other components and/or short circuiting anything.
Here are the cables that came with the device. The grabbers are color coded to make the installation as user friendly as possible.
The C64 Reloaded Adapter:
The Commodore 64 Reloaded boards (link) have ZIF sockets installed for most of the larger chips (except for those who opted for precision sockets during the email auction prior to the official release). If the C64 Reloaded is installed in a Commodore 64C case (link), the total height of the SIDFX will hinder the keyboard installation. To circumvent this problem, a special SIDFX Adapter can be purchased to reduce the height of the installation.
Mounting the Hardware:
Installation in a C64 Reloaded and a Commodore 64 Kickstarter case (identical to the beige Commodore 64 C cases). To ensure clearence between the motherboard and the device a self-adhesive rubber foot was mounted on the component in the middle section of the device as shown here.
The riser socket has to be moved from the SIDFX to the C64 Reloaded adapter in order to level things. If not, the board will be skewed like this (memo to self, RTFM!).
Before turning on the C64R, the motherboard must be configured as if a 6581 SID chip was installed to generate less heat during operation. This setting should be used regarless of the type of SID chip version is actually installed in the SIDFX.
It may look like a tight fit but there is plenty of room for a trouble-free installation…
How to mount the SIDFX in even more Commodore 64 machines on the next page…