The CBM-II has two incarnations, the P series (P = personal, or, home use) and the B series (B = business use). The B series was available with a built-in monochrome monitor (hi-profile) with detached keyboard, and also as a single unit with built-in keyboard but no monitor (lo-profile). These machines are often referred to as the "Porsche PETs" due to incorrect rumors that the case was designed by Porsche. Though Commodore did initially consult Porsche for a case design, it proved too expensive to produce, so Commodore enlisted designer Ira Velinski to create one based on the original PET prototype.[1][2][3][4]
The P-series uses the VIC-II 40-column color video chip like the Commodore 64 (C64). It also includes two standard Atari-style joystick ports. The 6509 CPU runs at 1MHz in the P-series due to the use of the VIC-II chip.
Both B and P-series machines have a 6581 SID chip, although the B-series' 2MHz clock speed makes it impossible to read any of the SID's registers.
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. Most models have the Motorola 68B45 installed which is a pin-compatible variant rather than the MOS 6545A1 2MHz part. On the B-series the 6509 CPU runs at 2MHz. The joystick ports are not present on the B-series, but the connector is still on the motherboard.
CBM-IIs are the only Commodore 8-bit machines with an RS-232 port instead of the standard user port. The I/O registers for the user port are still present (as they're an internal function of the 6522 chips) but there is no connector for it on the motherboard.
A cartridge slot is also included on the machines; however, no known cartridge software was developed.
The B-series retained the IEEE-488 interface from the PET instead of the IEC serial interface on the VIC-20 and C64. The small amount of software Commodore developed for the B-series was distributed on 500k 8050 format disks rather than the 170k 4040/1541 format.
Features common to both the P and B-series included a MOS Technology 6509 CPU, an enhanced version of the venerable 6502, that was capable of addressing up to 1 megabyte of RAM via bank switching (however, no CBM-II model came with more than 256 kilobytes of RAM). The sound chip is the 6581 SID, the same one that was used in the popular C64 but with some limitations as it was over-clocked to 2MHz. 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. The CBM-II's built-in operating system uses an enhanced version of CBM BASIC version 4.0.
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. A Z80 card was also announced if the user wished to run CP/M-80, as well as a Zilog Z8001 board, but none are known to exist. The 8088 board never reached production apparently because of difficulties getting it to work with the system.
The CBM-II line uses a complicated RAM banking scheme. Bank 0 contains the video RAM on P-series machines and is empty on B-series machines. Banks 1-4 contain the main system RAM, with Bank 15 containing the system ROMs, cartridge ROM, I/O registers, video RAM on B-series machines, and a small amount of RAM to store system variables. BASIC program text is stored in Bank 1. On 128KB models, Bank 2 contains all BASIC variables, however on 256KB models they're spread out among Banks 2–4. 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 1MB of RAM could be installed, but in practice the computer is limited to 256KB as the PLA chip does not have enough address lines for it. Passing data between different banks requires use of the register at $1 which selects the banks to be read from and written to via LDA (zero page),Y and STA (zero page),Y CPU opcodes. The register at $0 selects the bank where the CPU fetches instructions from, which will default to 15 ($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 64KB 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.
A Commodore CBM 610, the European version of a Commodore B128Connectors on the back of a CBM 610 reset, RS-232C, datasette, cartridge 44-pin, GND, audio, mains, IEEE-488, power switch, fuseMainboard and power supply of a CBM 610
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.
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 them are known to exist in private collections. At least one model, the P500, was commercially released in Europe but only sold in small numbers.
The most common of the B-series was the low-profile B128[1] (called the CBM 610 in Europe), which had 128 kilobytes of RAM. The B128 did not sell well, and ultimately Commodore's inventory was liquidated by Protecto Enterprizes, a large Commodore mail order dealer based in Chicago, Illinois.[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. Commodore did not release any sales figures or an official discontinuation date, however the B128/600 is the most common model in the lineup. Production ended at some point during 1984 and Commodore liquidated their remaining inventory in 1985. CBM-IIs were still being sold in Germany up to 1987. The exact number of CBM-IIs produced is unclear, however serial numbers indicate that at least 10,000 B128s were shipped along with a few dozen to a few thousand of the other models. It is believed that Commodore produced at least 5000–6000 of each machine.
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.[citation needed]
CBUG went on to develop a library of software for the computers. Its library, however, paled in comparison to the large software libraries enjoyed by the Commodore 64 and VIC-20.
The rounded case design of the high-profile CBM-II series would later be used in redesigned versions of the original PET/CBM computers, (such as the CBM8296) that the CBM-II line was designed to replace. In addition, the memory banking scheme of the CBM-II would be reused on the Commodore 128 with a few slight modifications.
Related Research Articles
The Commodore 1541 is a floppy disk drive which was made by Commodore International for the Commodore 64 (C64), Commodore's most popular home computer. The best-known floppy disk drive for the C64, the 1541 is a single-sided 170-kilobyte drive for 5¼" disks. The 1541 directly followed the Commodore 1540.
The Commodore 64, also known as the C64, is an 8-bit home computer introduced in January 1982 by Commodore International. It has been listed in the Guinness World Records as the highest-selling single computer model of all time, with independent estimates placing the number sold between 12.5 and 17 million units. Volume production started in early 1982, marketing in August for US$595. Preceded by the VIC-20 and Commodore PET, the C64 took its name from its 64 kilobytes(65,536 bytes) of RAM. With support for multicolor sprites and a custom chip for waveform generation, the C64 could create superior visuals and audio compared to systems without such custom hardware.
The Commodore 1571 is Commodore's high-end 5¼" floppy disk drive, announced in the summer of 1985. With its double-sided drive mechanism, it has the ability to use double-sided, double-density (DS/DD) floppy disks, storing a total of 360 kB per floppy. It also implemented a "burst mode" that doubled transfer speeds, helping address the very slow performance of previous Commodore drives.
The MOS Technology 6510 is an 8-bit microprocessor designed by MOS Technology. It is a modified form of the very successful 6502. The 6510 is widely used in the Commodore 64 (C64) home computer and its variants.
MOS Technology, Inc. ("MOS" being short for Metal Oxide Semiconductor), later known as CSG (Commodore Semiconductor Group) and GMT Microelectronics, was a semiconductor design and fabrication company based in Audubon, Pennsylvania. It is most famous for its 6502 microprocessor and various designs for Commodore International's range of home computers.
The Commodore 128, also known as the C128, C-128, C= 128, is the last 8-bit home computer that was commercially released by Commodore Business Machines (CBM). Introduced in January 1985 at the CES in Las Vegas, it appeared three years after its predecessor, the Commodore 64, the bestselling computer of the 1980s.
The VIC-20 is an 8-bit home computer that was sold by Commodore Business Machines. The VIC-20 was announced in 1980, roughly three years after Commodore's first personal computer, the PET. The VIC-20 was the first computer of any description to sell one million units. It was described as "one of the first anti-spectatorial, non-esoteric computers by design...no longer relegated to hobbyist/enthusiasts or those with money, the computer Commodore developed was the computer of the future."
The Commodore PET is a line of personal computers produced starting in 1977 by Commodore International. A single all-in-one case combines a MOS Technology 6502 microprocessor, Commodore BASIC in read-only memory, keyboard, monochrome monitor, and, in early models, a cassette deck.
The Commodore 16 is a home computer made by Commodore International with a 6502-compatible 7501 or 8501 CPU, released in 1984 and intended to be an entry-level computer to replace the VIC-20. A cost-reduced version, the Commodore 116, was mostly sold in Europe.
The Commodore Plus/4 is a home computer released by Commodore International in 1984. The "Plus/4" name refers to the four-application ROM-resident office suite ; it was billed as "the productivity computer with software built in".
Commodore BASIC, also known as PET BASIC or CBM-BASIC, is the dialect of the BASIC programming language used in Commodore International's 8-bit home computer line, stretching from the PET (1977) to the Commodore 128 (1985).
The VIC-II, specifically known as the MOS Technology 6567/6566/8562/8564, 6569/8565/8566 (PAL), is the microchip tasked with generating Y/C video signals and DRAM refresh signals in the Commodore 64 and Commodore 128 home computers.
The Commodore 65 is a prototype computer created at Commodore Business Machines in 1990–1991. It is an improved version of the Commodore 64, and it was meant to be backwards-compatible with the older computer, while still providing a number of advanced features close to those of the Amiga.
The Commodore RAM Expansion Unit (REU) is a range of external RAM add-ons.
The MOS Technology 8502 is an 8-bit microprocessor designed by MOS Technology and used in the Commodore 128 (C128). It is an improved version of the MOS 6510 used in the Commodore 64 (C64). It was manufactured using the HMOS process, allowing it to have higher transistor density, and lower cost, while dissipating less heat. The 8502 allows the C128 to run at double the clock rate of the C64 with some limitations.
The C64 Direct-to-TV, called C64DTV for short, is a single-chip implementation of the Commodore 64 computer, contained in a joystick, with 30 built-in games. The design is similar to the Atari Classics 10-in-1 TV Game. The circuitry of the C64DTV was designed by Jeri Ellsworth, a computer chip designer who had previously designed the C-One.
The Commodore 64 home computer used various external peripherals. Due to the backwards compatibility of the Commodore 128, most peripherals would also work on that system. There is also some compatibility with the VIC-20 and Commodore PET.
The MSD Super Disk were a series of 5¼-inch floppy disk drives compatible to some degree with the Commodore 1541 disk drive. produced by Micro Systems Development for use with Commodore 8-bit home computers. Two different versions of the MSD Super Disk were available: the single-drive model, SD-1; and the dual-drive model, SD-2.
The Commodore PC compatible systems are a range of IBM PC compatible personal computers introduced in 1984 by home computer manufacturer Commodore Business Machines.
The Commodore D9060/D9090 Hard Disks were the only family of hard drives that Commodore made for both the home and business market. The electronics are identical in the D9060 and the larger D9090 unit; the only difference is the size of the installed hard drive, with a jumper set to distinguish between 4 or 6 disk heads. Originally intended for the metal-cased PET/CBM series of computers, they are compatible with the VIC-20, Commodore 64 and later models with an adapter.
^a Neither the CBM128-80 nor the B128 are to be confused with the very different and reasonably successful Commodore 128 (also known as CBM 128 and C128), Commodore's final 8-bit home/personal computer, released in 1985.
^a The CBM-II, due to a quirk in the input, if you do the command "POKE 0,35" will lock everything, and all of the memory will be filled with 00's and FF's.
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
