Additions to the 6809 are shown with blue type.

* There are two additional 8-bit accumulators, E and F. These can be concatenated to form a 16-bit accumulator called W. The existing 6809 16-bit accumulator, D, can also be concatenated with W to form a 32-bit accumulator Q.

Despite the user-friendliness of the additional instructions, analysis by 6809 programming gurus indicates that many of the new instructions are actually slower than the equivalent 6809 code, especially in tight loops.

As a consequence of early pervasive design decisions taking advantage of the easily used reentrant object code capabilities of the 6809 processor, programs intended for OS-9 are required to be reentrant ; compilers produce reentrant code automatically and assemblers for OS-9 offer considerable support for it.

This is because the Z80 combines two full ( but short ) clock cycles into a relatively long memory access period compared to the clock, while the more asynchronous 6809 instead has relatively short memory access times: depending on version and speed grade, approximately 60 % of a single clock cycle was typically available for memory access in a 6809 ( see data sheets ).

When microprocessors ( CPU chips ) became available, SWTPC became one of the first suppliers of microcomputers to the general public, focusing on designs using the Motorola 6800 and, later, the 6809 CPUs.

This means it can be used with external DMA without needing refresh every 14 cycles as the 6809 does.

Instead of stacking the PC and CC registers ( normal 6809 behavior ) the FIRQ interrupt can be set to stack the entire register set, as the IRQ interrupt does.

Among the significant enhancements introduced in the 6809 were the use of two 8-bit accumulators ( A and B, which could be combined into a single 16-bit register, D ), two 16-bit index registers ( X, Y ) and two 16-bit stack pointers.

Since a CPU designer could hardly guarantee where this code would be located in a future system, the 6809 design focused heavily on support of position-independent, reentrant code that could be freely located anywhere in the memory map.

Software development company Microware developed the original OS-9 operating system ( not to be confused with the more recent Mac OS 9 ) for the 6809, later porting it to the 68000 and i386 series of microprocessors.

OS-9 has had a modular design from the beginning, influenced by notions of the designers of the 6809 and how they expected software would be distributed in the future ( see the three-part series of articles in Jan-Mar 1979 Byte by Terry Ritter, et al.

The MOS 65CE02 allowed the direct page to be moved to any 256 byte boundary within the first 64KB of memory by storing an 8-bit offset value in the new B ( block ) register, equivalent to the 8-bit 6809 DP ( direct page ) register.

Also more traditional " von Neumann based " single chip microcontrollers may be regarded as competitors, such as the 6800 / 6809 based Motorola 68HC11, the Hitachi H8 family, and Z80-derivatives, such as Toshiba TLCS-870, to name just a few.

Due to the limited address space of the 6809 ( 64 kB ) and hardware limitations, the main memory space for the UniFLEX kernel as well as for any running process had to be smaller than 56 kB ( code + data ).

Microware initially produced a version of BASIC and a real-time kernel for the Motorola 6800 processor, and was asked by Motorola to develop what turned into BASIC09 for the then-new Motorola 6809 processor.

The extended 8 KB version was then generalized into BASIC-80 ( 8080 / 85, Z80 ), and ported into BASIC-68 ( 6800 ), BASIC-69 ( 6809 ), and MOS Technology 6502-BASIC ( unfortunately spilling over to 9 KB, in an era when 8 KB ROM chips were standard ), as well as the 16-bit BASIC-86 ( 8086 / 88 ).

Based on the Namco Galaga hardware, this is the first of the Pac-Man games to use the Motorola 6809 processor, unlike the earlier Pac-Man games which used the older Z80, and fell into the conversion class of the Namco Galaxian.

In microcomputers, SWTPC's 6800 and 6809 machines used TSC's FLEX disk operating system, Radio Shack's TRS-80 machines used TRS-DOS, their Color Computer used OS-9, and most of the Intel 8080 based machines from IMSAI, MITS ( makers of the legendary Altair 8800 ), Cromemco, North Star, etc., used the CP / M-80 disk operating system.

The 6809 used the two-phase clock cycle directly as the basic machine cycle.

The 6809 was used in Commodore's dual-CPU SuperPET computer, and, in its 68A09 incarnation, in the unique vector graphics based Vectrex home video game console with built-in screen display.

The 6809 was used in the Milton Bradley Expansion ( MBX ) system, which was an arcade console which was used with the Texas Instruments TI-99 / 4A home computer.

The KONAMI-1 was a modified 6809 used by Konami in various arcade sets such as The Simpsons.

The 6809 CPU was also used in traffic signal controllers made in the 1980s by several different manufacturers.

Series III of the Fairlight CMI ( computer musical instrument ) used dual 6809 CPUs and OS9, and also used one 6809 CPU per voice card.

Additionally, the 6809 processor was used in the late 1980s through the early 2000s in Motorola Smartnet Trunking Controllers ( dubbed the 6809 controller ).

In computing, the SEX assembly language mnemonic has often been used for the "" machine instruction found in the Motorola 6809.

Several other buses were designed with minor improvements on the S-100 bus: the 50-pin " Benton Harbor Bus " used in the Heathkit H8 ; the SS-50 Bus used in a variety of 6800 and 6809 computers.

The game also used multi-core processing, which included two Z80 microprocessors, one 6809 microprocessor, and one 8039 microprocessor, and for the sound, five AY-3-8910 PSG sound chips and a DAC.

Some 6809 opcodes also live on in the Freescale embedded processors.

6809 programming model, showing the processor register s.

However, the decisions made by the design team made for a very powerful processor and made possible advanced operating systems like OS-9 and UniFlex, which took advantage of the position-independent, re-entrant nature of the 6809 to create multi-user multitasking operating systems.

Williams also utilized the processor in many of its solid-state pinball machines ; a specialized version of the 6809 CPU formed the core of the successful Williams Pinball Controller.

Some processor architectures, such as the Motorola 68000, Motorola 6809, WDC 65C816, Knuth's MMIX, ARM and x86-64 allow referencing data by offset from the program counter.

A series of interchangeable expansion cards were then developed: additional RAM cards ; a card containing a BASIC interpreter on ROM ; a 40 × 25 character VDU card, and a UHF adaptor for it ; interface cards ; a floppy disk controller ; Econet network cards ; an 80 × 25 character VDU card ; and later also alternate processor cards, offering a 6809 or a faster 6502.

While in " Emulation Mode " it is fully compatible with the 6809.

The Motorola 6809 is an 8-bit ( with some 16-bit features ) microprocessor CPU from Motorola, designed by Terry Ritter and Joel Boney and introduced 1978.

The 6809 was source-compatible with the 6800, though the 6800 had 78 instructions to the 6809's 59.

The Hitachi 6309 was an enhanced version of the 6809 with extra registers and additional instructions, including block move, additional multiply instructions and hardware-implemented division.

* German electronics manufacturer Eltec has been manufacturing the Eurocom-model CPU boards for industrial purposes since the late seventies, starting with the 6802 and 6809 Eurocom-1 and Eurocom-2, and onwards with 68K, and derivative, CPU boards up to today.

The downside of the system was that it required much more advanced decoders, typically featuring Zilog Z80 or Motorola 6809 processors with RGB and / or RF output.

By about 1980, TSC had developed a Unix-like multi-user, multi-programming operating system ( UniFlex ), for 6809 systems with DMA 8 " floppy disks and extended memory.

Processors with 16-bit addressing ( Z80, 6502, 6809, etc.

In 1982, Gyruss, known for its stereo sound and musical score, utilized multi CPUs, which included two Z80 microprocessors, one 6809 microprocessor, and one 8039 microprocessor, along with five AY-3-8910 sound chips and a DAC for the sound.

Four GMS 204 units were controlled from a 6809 microprocessor, with the program stored in a solid-state plug-in memory module.

TSC never bundled a C compiler with UniFLEX for the 6809, though they produced one.