TurboProcessor Upgrade and Installation

This page describes how to install and configure the TurboProcessor board into a custom case. Whilst exposed circuit boards look cool, I was a little worried about dropping something on the board and damaging it. The TurboProcessor was sold by Swisscomp in the USA, but it was actually made by a Rossmoller in Germany and marketted there as TurboProcess. It was a 4MHz external CPU upgrade, a predecessor to the Flash8 (only sold in Germany) and the benchmark which CMD improved on to design and build the SuperCPU. Like the SuperCPU it uses a 65816 processor.

The TurboProcessor takes a little bit of tuning to get it to work with some C64 motherboards (it won't work on some) and seems not to work with the C128 at all.
In addition to building a case for the device, I wanted to upgrade the ROM to JiffyDOS (transferred my machine's existing licence) with 64HDD's enhanced PwrLoader.

The case is available locally to me, if you want one send me an email to find out about pricing. The EPROM is also available as an upgrade option.


Build the system:

Inside the case: - the case requires a reasonable amount of modification to remove some posts and other bits of plastic which get in the way.

The TurboProcessor board requires removal of the rechargeable battery (mine didn't work after all these years) and also removal of the reset switch.

Mounting the board: - the TurboProcessor circuit board conveniently has several mounting holes. I used a piece of thick plastic to build a bridging board between these holes and the screw posts on the casing - thus not needing to modify the circuit board at all.

To the rear of the main board I installed a second circuit board with a socket (future LED driver chip) and made the necessary connections to this board. The connections to the TurboProcessor are made using a 10pin header so that I can disconnect the board from the case easily.

Most switches are wired either directly to the DIP switch block or to the RESET switch pads.

ROM Upgrade: - Of course I wanted to have JiffyDOS and 64HDD's PwrLoader installed, so I created this custom EPROM. The three-position ROM switch I've installed allows selection of two kernals and the 16k expansion ROM mode (though I have nothing programmed there). Even though the TurboProcessor runs at 4MHz, PwrLoad is only about 2x faster than standard because of the slow downs the 65816 must do when accessing the C64 I/O chips.

Only 64k of SRAM is installed on the TurboProcessor, but I'm thinking about upgrading mine to 512kB or 1024kB when I get some chips.

Switches: - standard toggle and push button switches are used. There's Enable/Disable, 1-4MHz and 3-way ROM select toggle switches, and a push-button for RESET (from top-left to bottom-right).

Nothing fancy yet as far as flashing LEDs or a 1-4MHz speed indicator, but the possibilities are endless for someone who just must have these!

Outside the case: - If you want, the case can be left bare - and it looks quite neat that way.

Stickers: - I decided however to dress the case with a custom designed sticker so I could easily identify what was in the case, and also remind myself as to what all the switches do.