MEGA65 Welcome Guide
MEGA65 only uses one SD memory card at a time. If there is a microSD card in the external slot, it ignores the full-size
SD card in the internal slot. The SD card contains the operating system software (“ROM”), firmware (“cores”), and
D81 disk images.
I recommend installing a microSD card in the external slot, and leaving the internal card with its factory-installed data
intact. Following this Guide, you will set up a microSD card with all of the latest versions of the software. You will
use this card to transfer software and data between MEGA65 and your PC.
Note: Many features of the MEGA65 expect short MS-DOS-style filenames for files on the SD card: a maximum of
8 characters, a dot, then a maximum of 3 characters (myprogra.prg).
Some features will handle files with longer names, but just not display the full name in menus. The Freeze menu and
core selection menu (discussed later) do this.
Some features such as loading SD card files from BASIC (DLOAD "MYPROGRA.PRG",U12) will fail for files with longer
names. The only solution is to rename the file to use a short name using your PC.
(This does not apply to files on CBM disk images, which have their own unrelated limitations on names.)
Tip: The User Guide’s explanation of SD cards begins on page 23.
4.2 Cores
The MEGA65 is powered by a Field Programmable Gate Array (FPGA). An FPGA is a special kind of chip that
can be programmed to perform the functions of most any integrated circuit (IC). Like an IC, it is fast, and interacts
electronically with the rest of the hardware. Unlike an IC, it can be reprogrammed with new logic at any time. FPGA
code is sometimes referred to as firmware, a term you may recognize from modern computers and other devices.
MEGA65’s FPGA is programmed to behave like the complete collection of ICs you would find in a Commodore 65:
the CPU, video and sound chips, and so on.
The MEGA65 team continues to make improvements to this firmware, and you will want to update your machine
with new firmware as updates become available. Other contributors are developing alternate FPGA programming to
simulate other computers, such as a Commodore 64.
To make managing multiple sets of firmware easy, MEGA65 describes each set as a core. You will download a core
data file (described in the manual as a bitstream), copy the file to the microSD card, and follow a procedure to install
the core in one of seven user-accessible slots. You can access a menu to tell MEGA65 which core to use.
The MEGA65 always retains a copy of its original factory core (in “slot 0”). If something goes wrong while updating
another core, you can always go back to the original version.
Tip: This Welcome Guide will describe how to upgrade the MEGA65 core to the latest version. For more general
information about cores, see the User’s Guide, chapter 6, starting page 47.
26 Chapter 4. Important concepts
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