David-65 - a 6502 extender board

[Diddl]

Nils from "For8Bits" is developing a new hardware for PET and CBM computers.

It is very similar to Final Expansion for VIC-20 but it is more universal useable. David-65 works on every 6502 board: PET, CBM, VIC-20, any Commodore Floppy ...

Simply do following to install David-65:

   
• remove 6502 CPU (hope it has a socket)
• insert David-65 into CPU socket
• insert CPU into David-65 board

David-65 offers nearly same features than a FE3:

   
• CPLD for programmable memory configuration
• additionally 512 Kb SRAM
• additionally 512 Kb Flash  (programmable)
• a RS-232, very slow only for debugging (software driven like in a C-64)
• a LED for diagnostic purposes

What are the benefits for using a David-65:

   
• extension of a PET / CBM
  
  Any PET or CBM with 8KB or 16KB will have 32KB also
  
  If RAM or ROM (or both) is damaged David-65 will replace it without soldering
  
  You can choose between any BASIC, any Kernal and any Software extension (ExBasic, Assembler, ...). You can switch between different editor ROM and different languages. And of course any RAM configuration, also for normally ROM address ranges.
  
  New Software can use whole 1MB of the Davuid-65 memory
  .
  
• Diagnostic
  
  David-65 can start with own Flash and own RAM, so nearly no "external" hardware is nessecary. Only power and clock for the CPU is nessecary to run diagnostic.
  
  A badly hard damaged 6502 system could be analysed from CPU's sight. Even if Kernel or Zeropage is damaged, David-65 will find it out.
  .
• Ultimative Speeder for a 1541 drive
  
  My personal favourite goal is the ultimate speeder for a floppy drive. Davied-65 can hold tw0 D64 Images or one D71 image. Installed in a 1541 floppy David-65 can read whole disk into memory and so access data in RAM disk like speed. Write access goes into RAM and will be written in idle time (lazy write back).
  .
• David-65 can act as a standalone 6502 board if a 5V power and a clock is available ...

Many other things are possible with David-65, cause CPLD design makes it possible to adapt it to any 6502 system.

[polishedball]

This would be very nice,  does he keep an active development page somewhere?

[for(;;)]

Not yet.

Should create one, but everything's still very early alpha stage...

[for(;;)]

Here's the latest schematic.

You are very welcome to post any questions / suggestions...

[for(;;)]

Corrected some errors.

Memory access is now independend from the host by separating data- and address busses.
That means, on memory access to David65's memory, the host computer sees a read access to $FFFF.

U10 and U11 are deselected then and the resistor networks pull-up the address lines to $FFFF.

This was necessary to avoid side effects of reading any addresses within the host system, e.g. resetting IRQ flags of VIA chips.

[Diddl]

CPLD designs for PET /CBM and floppy drives (1541/1571) are finished.

it is possible to flash CPLD design by a connected Bumble-B directly in David-65. So updates and changes are possible without a JTAG programmer.


David-65 also gets a highspeed connection port. Together with a Bumble-B it is possible to connect a PC by USB and transfer Data directly between 6502 and PC.


I'm in contact with a member of VICE team. It seems VICE will emulate David-65 in future!

The Final Expansion 3 already is emulated in VICE, thanks to VICE Team!!