replacement rom adapter for the commodore 64
This is a rom adapter board for the C64 which replaces all rom chips with a single 64kb 27C512 Eprom, offering space for four different kernals, four charsets and two basic roms. Any combination of roms can be chosen using control lines provided on the board. A GAL16V8 decodes the chip select signals from the board and addresses the eprom accordingly.
As far as the C64 rom chips are concerned, there a two different basic types of mainboards: the older revisions (up to and including 250466) use three separate 24-pin rom chips layed out next to each other. The newer revisions (250469) combine kernal and basic rom in a single 28-pin rom next to the charset rom.
This is a single board layout that can be used for all c64 mainboard types. By soldering in pin headers and jumper wires in different locations, the resulting build will be usable in either old or new boards. In old boards, the adapter will sit in the kernal socket, and plug into the basic and charset sockets to the left and right for the chip select signals. In new boards, the adapter will sit in the combined kernal and basic socket, and only plug into the charset socket to the left.
- Ordering Assembly Kits
- Eprom Layout & Control
The source distribution includes the source for the 16V8GAL logic as well as schematics and pcb layouts in KiCad format.
Latest stable is reprom64-1.3.tar.gz.
All releases can be found under /download/reprom64
Latest developments are available via github:
git clone https://github.com/hbekel/reprom64
- reprom64-firmware-1.3.jed (JEDEC file for the GAL16V8)
- reprom64-gerber-r3.zip (Gerber files for revision 3)
Ordering Assembly Kits
I’m offering assembly kits including a reprom64 pcb, a preprogrammed GAL and all required components (except connection cables or switches) for 10€ each. Worldwide shipping via regular mail is free of charge.
You can order kits via email at email@example.com
To place an order, please include the word “reprom64” in the subject. State your full name, your complete international shipping address and the number of kits you wish to buy. Note that orders are limited to a maximum of two kits per person. You will receive an email containing payment information (bank transfer only). You will have to pay in advance to confirm your order.
Notes on availability
I try to keep a sufficent number of kits on stock, but please note that I’m doing all of this in my spare time, on a short budget and a minimal profit margin. My primary motivation is to serve the community, not to run a profitable business.
This means that in case I am currently out of stock, it may take a few weeks until I can put together a new batch of kits to fullfill your order. I may even need to collect a sufficient number of prepaid orders before I can afford to order the necessary parts myself. In these cases I will regularily inform you about the status of your order. Thus some patience and trust may be required on your part.
Depending on the mainboard type, pin headers and jumper wires have to be soldered at different positions. Please select your board type from the checkbox below:
Jumper wires (bridges)
The pin headers are soldered from the top. All other parts are soldered from the bottom side.
It is recommended to first insert all the pin headers into the mainboard sockets and then put the adapter board on top to solder the first few pins. This will ensure that the board will fit nicely into the sockets regardless of possible small variations in socket and pin header spacing.
Please note that adress bus signals A5 and A8 available on the right side of the board do not have to be connected at all for the proper operation of the Reprom64. They are provided simply as a convenient place to access these signal in case you want to install other hardware that needs them. For example, stereo SID adapter boards typically need access to A5 and A8.
List of parts
|U1||27C512 + Socket||64kb||DIP-28|
|U2||GAL16V8D-15LP + Socket||-||DIP-20|
|P1||Precision Pin Header straight||40pin||2.5mm|
|P2 P3 P4||Pin header angled||2pin||2.5mm|
Eprom Layout & Control
The table below shows the eprom layout and the corresponding control line states. The control lines are available at the pin headers labeled BASIC, CHARSET and KERNAL, where bit 1 is available at the left pin and bit 0 is available at the right pin, except for the Basic pin header which provides bit 0 at both pins.
The control lines are pulled high by the internal pullup resistor of the 16V8GAL. Thus simple SPST switches to ground can be used to select the desired ROM. If left open or unconnected, the line is driven high (1), if closed, the line is driven low (0).
reprom64 Hardware and Firmware Copyright (c) 2015, Henning Bekel <firstname.lastname@example.org> GNU GENERAL PUBLIC LICENSE Version 2, June 1991 Copyright (C) 1989, 1991 Free Software Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. Preamble The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation's software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too. 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