| | podobné slovo | definícia |
mc68000
(foldoc) | Motorola 68000
68000
MC68000
(MC68000) The first member of Motorola, Inc.'s
family of 16- and 32-bit microprocessors. The successor to
the Motorola 6809 and followed by the Motorola 68010.
The 68000 has 32-bit registers but only a 16-bit ALU and
external data bus. It has 24-bit addressing and a {linear
address space}, with none of the evil segment registers of
Intel's contemporary processors that make programming them
unpleasant. That means that a single directly accessed
array or structure can be larger than 64KB in size.
Addresses are computed as 32 bit, but the top 8 bits are cut
to fit the address bus into a 64-pin package (address and data
share a bus in the 40 pin packages of the 8086 and {Zilog
Z8000}).
The 68000 has sixteen 32-bit registers, split into data and
address registers. One address register is reserved for the
Stack Pointer. Any register, of either type, can be used
for any function except direct addressing. Only address
registers can be used as the source of an address, but data
registers can provide the offset from an address.
Like the Zilog Z8000, the 68000 features a supervisor and
user mode, each with its own Stack Pointer. The {Zilog
Z8000} and 68000 are similar in capabilities, but the 68000 is
32 bits internally, making it faster and eliminating forced
segmentations.
Like many other CPUs of its generation, it can fetch the next
instruction during execution (2 stage pipeline).
The 68000 was used in many workstations, notably early
Sun-2 machines, and personal computers, notably {Apple
Computer}'s first Macintoshes and the Amiga. It was also
used in most of Sega's early arcade machines, and in the
Genesis/Megadrive consoles.
Variants of the 68000 include the 68HC000 (a low-power HCMOS
implementation) and the 68008 (an eight-bit data bus version
used in the Sinclair QL).
["The 68000: Principles and Programming", Leo Scanlon, 1981].
(2003-07-11)
|
mc68010
(foldoc) | Motorola 68010
MC68010
A microprocessor from Motorola. It was the
successor to the Motorola 68000 and was followed by the
Motorola 68020. Some instructions which were previously
user mode were made system mode, which necessitated
patches to a few programs.
The 68010's main advantage over the 68000 was that it could
recover from a bus fault. The 68000 microcode didn't save
enough state to restart all instructions; the 68010 corrected
this fault. This allowed it to use paged virtual memory.
The 68010's DBxx (decrement and branch) instructions could
hold and execute the preceding instruction in the {prefetch
buffer}, allowing some two-instruction loops to execute
without refetching instructions.
At one time there was a 68010 variant that was pin-for-pin
compatible with the 68000. Early Amiga hackers replaced
their 68000s with 68010s in order to get a small performance
increase.
(1995-11-29)
|
mc68020
(foldoc) | Motorola 68020
68020
MC68020
A microprocessor from Motorola. It was the
successor to the Motorola 68010 and was followed by the
Motorola 68030. The 68020 has 32-bit internal and external
data and address buses and a 256-byte instruction buffer,
arranged as 64 direct-mapped 4-byte entries[?].
The 68020 added many improvements to the 68010 including a
32-bit ALU and external data bus and address bus, and
new instrucitons and addressing modes. The 68020 (and
68030) had a proper three-stage pipeline.
The new instructions included some minor improvements and
extensions to the supervisor state, some support for
high-level languages which didn't get used much (and was
removed from future 680x0 processors[?]), bigger (32 x 32-bit)
multiply and divide instructions, and bit field manipulations.
The new adderessing modes added another level of indirection
to many of the pre-existing modes, and added quite a bit of
flexibility to various indexing modes and operations.
The instruction buffer (an instruction cache) was 256
bytes, arranged as 64 direct-mapped 4-byte entries. Although
small, it made a significant difference in the performance of
many applications.
The 68881 and the faster 68882 FPU chips could be used with
the 68020.
The 68020 was used in many models of the Apple Macintosh II
series of personal computers and Sun 3 workstations.
(2001-03-07)
|
mc68030
(foldoc) | Motorola 68030
68030
MC68030
A 32-bit microprocessor in Motorola's
Motorola 68000 family, with on-chip split instruction and
data cache of 256 bytes each. The 68030 has an on-chip
MMU (except in the 680EC30 version).
The 68881 and the faster 68882 FPU chips could be used with
the 68030.
The 68030 was the successor to the Motorola 68020, and was
followed by the Motorola 68040.
The 68030 is used in many models of the Apple Macintosh II
series of personal computers.
(2001-01-08)
|
mc68040
(foldoc) | Motorola 68040
68040
MC68040
(MC68040) A microprocessor from Motorola. It
was the successor to the Motorola 68030 and was followed by
the Motorola 68060.
The 68040 was the first 680x0 family member with an on-chip
FPU. It also had split instruction and data caches of 4
kilobytes(?) each. It was fully pipelined, with six stages.
The 68040 was used in the Apple Macintosh Quadra series of
personal computers.
The MC68LC040 is an MC68040 without a built-in FPU, and the
MC68EC040 is an MC68040 without an MMU or FPU.
(2003-10-25)
|
mc6809
(foldoc) | Motorola 6809
6809
MC6809
(MC6809) An eight-bit microprocessor from {Motorola,
Inc.}.
The 6809 was a major advance over both its predecessor, the
Motorola 6800 and the 6502. The 6809 had two 8-bit
accumulators, rather than one in the 6502, and could combine
them into a single 16-bit register. It also featured two {index
registers} and two stack pointers, which allowed for some very
advanced addressing modes. The 6809 was source compatible
with the 6800, even though the 6800 had 78 instructions and the
6809 only had around 59 (including a SEX instruction). Some
instructions were replaced by more general ones which the
assembler would translate and some were replaced by {addressing
modes}.
The 6809 had one of the first multiplication instructions of the
time, 16-bit arithmetic and a special fast interrupt. But it
was also highly optimised, gaining up to five times the speed of
the 6800 series CPU. Like the 6800, it included the undocumented
HCF (Halt and Catch Fire) bus test instruction.
The Hitachi 6309 was a version with extra registers. The
6809 was used in the UK "Dragon 32" personal computer and
was followed by the Motorola 68000.
Usenet newsgroup: news:comp.sys.m6809.
Lennart Benschop posted a
emulator (originally called "usim") and a cross-assembler to
Usenet newsgroup alt.sources on 1993-11-03. Ray P. Bellis
released a version 0.11.
Benschop emulator (http://lennartb.home.xs4all.nl/m6809.html).
(2014-06-24)
|
philips scc68070
(foldoc) | Philips SCC68070
A microprocessor which is object code
compatible with the Motorola 68000. It is not a performance
improvement over the 68060; it's performance rather resembles
that of the 68000.
(1995-04-22)
|
|