Commodore CBM-II
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| Type | Personal computer |
|---|---|
| Release date | 1982 |
| Discontinued | 1984 |
| Operating system | Microsoft BASIC 4.0 |
| CPU | MOS Technology 6509 @ 1 or 2 MHz, Intel 8088 or Zilog Z80A @ 4 MHz option |
| Memory | 128 or 256 kB |
| Graphics | VIC-II (320 × 200, 16 colors, sprites, raster interrupt) or 6545 CRTC |
| Sound | SID 6581 (3× Osc, 4× Wave, Filter, ADSR, Ring) |
| Connectivity | RS-232, A/V, Digital tape, ROM cartridge, Audio minijack, Mains power, Parallel IEEE-488 Floppy/Printer |
The Commodore CBM-II series is a short-lived range of 8-bit personal computers from Commodore Business Machines (CBM), released in 1982 and intended as a follow-on to the Commodore PET series.
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 known as the "Porsche PETs" for their unique styling.
The P-series uses the VIC-II 40-column color video chip like the C64. It also includes two standard Atari-style joystick ports. The 6509 CPU runs at 1 MHz in the P-series due to the use of the VIC-II chip.
Both B and P-series machines have an 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 2 MHz part. On the B-series the 6509 CPU runs at 2 MHz. 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. IEC drives will require an adapter as well as a modified kernal ROM. 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 an 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, 1/4 megabyte). The sound chip is the 6581 SID, the same one that was used in the popular Commodore 64 (C64) but with some limitations as it was over-clocked to 2 MHz. 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.
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