banks to be read from and written to via LDA (zero page),Y and STA (zero page),Y CPU opcodes. The register at $1 selects the bank where the CPU fetches instructions from, which will default to 15 ($F) on power up. The BASIC included with the CBM-II series is known as BASIC 4.0+. It contains the enhanced BASIC 4.0 disk commands as well as a few other added features for structured programming and error trapping. Commodore had plans for a wide variety of RAM configurations as well as slimline and "high profile" models. 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. No production machines had internal floppy drives, however these likely would have been a half-height variant of the 8050. Most of the planned CBM-II models never made it past the prototype stage. Originally, there would be four models in each series, with memory increasing in 64 KB increments. 64k and 192k models were dropped early in development and no such models were produced. In the end, the only CBM-II models to enter production and be sold to end users were the B128/600, B256/700, CBM-128/710, and PAL model P500s. The B128 and P500 were slimline models with no internal disk drives or attached monitor while the CBM 128 and B256 were high-profile models. The B128 was the biggest selling of the three. The production naming within the United States and Canada was the B128/B256 and CBM128-80/CBM 256-80 while in Europe they were known as the 600 and 700 series respectively (no "B" in front of the model number). The P machine was known worldwide as the 500 series. There are prototype models though such as the B500 (earlier B128 design) and B700 (earlier CBM 128-80/CBM 256-80 design) known to exist. History Due to the popularity of the C64, the P-series was cancelled in the United States before it could be officially released; however, a few dealers who received preproduction units sold them. As the P-series had not then been certified by the FCC, Commodore were threatened with legal action and were forced to recall them. It was rumored that all recalled P-series machines were destroyed, however a handful of