Commodore CBM 720 (B256-80)
The Commodore CBM 720 has 256KByte RAM, just like the CBM 730 but lacks the co-processor board that allowed for an optional 8088 The difference with the CBM 620 is the new graphics ROM that provides 8x14 pixel based letters as opposed to the 8x8 pixel based characters in the 620. The 720 also has a detachable keyboard, allowing for a more ergonomic set-up.
Commodore CBM 700 Series
The Commodore 700 series was introduced in 1982 and sold under a few different names. In the US they were sold as the B256 and PET 700 series, in Europe as the CBM 700 series, or CBM 256-80 / B256-80.
The hardware is identical to the CBM 600 series. The machines had an integrated monitor, detachable keyboard and two 5.25" disk drives. The BX256 model was capable of supporting an optional 8088 chip. Graphics and sound capabilities were also identical to the CBM series, except that the 700s had a new character generator ROM, and graphics were generated off an 8x14 matrix. The Kernal ROM determined which generator to use based on inputs that were hard-soldered on the main board.
MOS 6509 CPU
THe MOS Technology 6509 is an enhanced version of the 8-bit 6502 CPU. Using bank switching the 6509 is able to address up to 1MByte of RAM. The 6502 also could do bank-switching, but did so via separate logic circuits, the 6509 had this logic built in. This extra logic made the 6509 difficult to program, and it was mainly used in the Commodore CBM-II line of computers.Source:WikiPedia - MOS Technology 6509
Source:WikiPedia - MOS Technology 6502
SID (MOS 6581) - Sound Interface Device
SID is short for Sound Interface Device. It is the name of the sound chip that was used in the VC10, the commodore 64 and the Commodore 128. SID was developed by Bob Yannes, an employee of MOS Technology. Bob was not only an engineer but also knew a lot about music. His intention was to create a different sound chip than other devices at the time. He implemented a subtractive synthesis chip. The chip's distinctive sound is easily recognized and was clearly ahead of the ocmpitition. The SID combines analog and digital circuitry that cannot be 100% emulated, even today.Source: C64 Wiki