The B-series uses a 6545 CRTC video chip to give an 80-column "green screen" monochrome output more suitable for word processing and other business use than the VIC-II's 40-column display.

Additionally, the CBM-II has an industry-standard RS-232 serial interface and an IEEE-488 parallel bus (for use by disk drives and printers) just like the PET/CBM series.

An optional Intel 8088-based coprocessor board allows the CBM-II series to run CP/M-86 1.1 and MS-DOS 1.25; however, the computers were not IBM PC compatible and very little, if any, software taking advantage of this capability ever appeared.

The coprocessor board only runs on high-profile machines due to power supply and mechanical spacing requirements.

However, unlike the later released Commodore 128, the CBM-IIs do not have the system ROMs mapped into banks other than 15, which has very limited program RAM (1k free, plus a 4k expander board could be installed).

This meant that software had to include its own OS routines to handle device I/O and interrupts, as it is not possible to "far call" code across different memory banks.

In theory, if Banks 5–14 were filled, up to 1 MB of RAM could be installed, but in practice the computer is limited to 256 KB as the PLA chip does not have enough address lines for it.

It contains the enhanced BASIC 4.0 disk commands as well as a few other added features for structured programming and error trapping.

The slimline machines were all-in-one units while the high-profile models had a separate keyboard and attached swivel-mount monitor.

Both slimline and high-profile models have a connector for internal floppy drives and coprocessor boards, although only the latter have physical room in the case and a sufficient power supply for them.

[6] The Protecto ads for the B128 bundle, including a dual disk drive, monitor and printer, appeared in various computer magazines for several years.

The CBM-II line sold poorly and ended up being extremely expensive to manufacture, as well as difficult to develop software for.

After discontinuing the CBM-II range, Commodore handed its documentation, schematics, and all other information over to CBUG, the Chicago B128 Users Group.

Among these materials was a prototype motherboard using an Intel 8088 processor, which hints at the possibility the line could have been made IBM compatible if production had continued.