Tech Stuff

Overview:

CPU:
ROM:
RAM:
Sound:

Display:

Storage:

Keyboard:


Other:

6510, 0.985 MHz (PAL) and 1.02 MHz (NTSC).
20 Kbytes.
64 Kbytes.
SID 6581, 3 channels of lovely sound. The chip is very impressive for it's time. [more]
VIC-II, 16 colours, text resolution at 40 x 25. Graphics resolution at 320 x 200. [more]
Tape interface or a 5 1/4" floppy drive that can store 170k/side. [more]

Non-standard ASCII, 66 keys.

  • Cartridge Expansion slot.
  • User connector.
  • Two joystick ports.
  • TV connector (RF modulator, also transmits audio to the TV).
  • RGB/composite monitor connector (includes sound output).
  • Serial port for connecting printers and floppy drives.

SID: (Sound Chip)
The 6581 Sound Interface Device (SID) is a single-chip, 3-voice electronic music synthesizer/sound effects generator compatible with the 65XX and similar microprocessor families. SID provides wide-range, high-resolution control of pitch (frequency), tone color (harmonic content), and dynamics (volume). Specialized control circuitry minimizes software overhead, facilitating use in arcade/home video games and low-cost musical instruments. Please note that the SID is not a FM-based synthesizer, like the Yamaha OPL series !!

Display:
Handled by the VIC-II chip (the enhanced version of the VIC, used on the Commodore VIC-20). 16 colours, text resolution at 40 x 25. Graphics resolution is 320 x 200. Smooth hardware-supported sprites with collision control, hardware scrolling, etc.

320 x 200 is only in hires mode, where the system is restricted to 2 colours from the 16-colour palette per 8x8 block.This comes from a single colour map whose location can be user-defined. An extra mode called multicolour can do 4 colours per 8x8 block using bitpairs (but this halves the horizontal graphics resolution - i.e. double length pixels).

There are at least three additional video modes that can be addressed by multiplexing the VIC-II chip, but these are timing-critical and modes that work well with PAL may not work on NTSC (and vice versa). Some of these extra modes include FLI, IFLI, MCI and IMAP (IMAP being one of the few that is both PAL and NTSC compatible without modifications in the display routine). These routines are very CPU-intensive, and naturally aren't built into the VIC-II. Their enhancements vary, but most are able to break the "number-of-colours-per-8x8-cell" requirement.

You can read more about graphic modes in "A Brief Description Of Graphic Modes" under the Gallery section of area64.

Storage

Note:
On the C64, the tape port (and drive)'s actual read rate is 1100-1200 baud. Data is written twice, and is accompanied by a CRC checksum code. This slows down the process to give or take 300 baud. CBM was the first (and last) computer company to have this feature in tape drives. This process has a drawback, however, and that is that the whole process is very intensive, and so all unnecessary functions are temporarily terminated. There no longer is a screen write, sound write, keyboard read (limited solely to the scan of the RUN/STOP key), and the jiffy clock (TI; TI$) is also stopped, which can wreck a program's tape load execution. Because of this, the more expensive disk drives became popular, and contrary to popular belief, they weren't popular only because of faster loading times for more data... even though that should have been the reason.