Zilog
Zilog, Inc. is an American manufacturer of microprocessors and 8-bit and 16-bit microcontrollers. It is also a supplier of application-specific embedded system-on-chip (SoC) products.
Its most famous product is the Z80 series of 8-bit micropro ...
's
32-bit
In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in 32- bit units. Compared to smaller bit widths, 32-bit computers can perform large calculati ...
processor
Processor may refer to:
Computing Hardware
* Processor (computing)
**Central processing unit (CPU), the hardware within a computer that executes a program
*** Microprocessor, a central processing unit contained on a single integrated circuit (I ...
, first released in 1986. It is essentially a 32-bit expansion of its
16-bit
16-bit microcomputers are microcomputers that use 16-bit microprocessors.
A 16-bit register can store 216 different values. The range of integer values that can be stored in 16 bits depends on the integer representation used. With the two ...
multiprocessing
Multiprocessing is the use of two or more central processing units (CPUs) within a single computer system. The term also refers to the ability of a system to support more than one processor or the ability to allocate tasks between them. There ar ...
capability, a six-stage
instruction pipeline
In computer engineering, instruction pipelining or ILP is a technique for implementing instruction-level parallelism within a single processor. Pipelining attempts to keep every part of the processor busy with some instruction by dividing inco ...
memory address
In computing, a memory address is a reference to a specific memory location used at various levels by software and hardware. Memory addresses are fixed-length sequences of digits conventionally displayed and manipulated as unsigned integers. ...
ing system can access 4
gigabyte
The gigabyte () is a multiple of the unit byte for digital information. The prefix '' giga'' means 109 in the International System of Units (SI). Therefore, one gigabyte is one billion bytes. The unit symbol for the gigabyte is GB.
This definit ...
s of
RAM
Ram, ram, or RAM may refer to:
Animals
* A male sheep
* Ram cichlid, a freshwater tropical fish
People
* Ram (given name)
* Ram (surname)
* Ram (director) (Ramsubramaniam), an Indian Tamil film director
* RAM (musician) (born 1974), Dutch
* ...
. It can execute code written for the Z8000, but is not compatible with the Z80.
Described at the time as a "
mainframe
A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterprise ...
on a chip", the processor is in many ways an equivalent to
Intel
Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 ser ...
's
80386
The Intel 386, originally released as 80386 and later renamed i386, is a 32-bit microprocessor introduced in 1985. The first versions had 275,000 transistorsregisters, but expanded from the Z8000's 16-bit to 32-bit. Like the Z8000, the Z80000 allows its registers to be combined, in this case using two 32-bit registers to act as a single 64-bit one. To support the Z8000s 16-bit wide data, the Z80000 can place two 16-bit values in a single 32-register.
The processor includes a
memory management unit
A memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware unit having all memory references passed through itself, primarily performing the translation of virtual memory addresses to physical a ...
virtual memory
In computing, virtual memory, or virtual storage is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a very ...
addressing for temporary storage of RAM on a
hard disk
A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magn ...
. The processor has three methods of accessing memory:
* compact mode – meant for small programs, could only access 64 KB (16-bit addresses, equivalent to the Z8000's non-segmented mode). Address bits 31-16 of all virtual addresses comes from address bits 31-16 of the program counter.
* segmented mode – 32,768 segments of 64 KB (16-bit address; comprising memory from 0-2GB) ''and'' 128 segments of 16 MB (24-bit address; comprising memory from 2GB-4GB), making a total of 4 GB (32-bit address) of accessible memory.
* linear mode – direct 4 GB (32-bit address) accessible memory
The processor is designed to interoperate with other
integrated circuit
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
s designed for use with the Z8000, such as the Zilog Z8070
floating-point
In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can ...
coprocessor
A coprocessor is a computer processor used to supplement the functions of the primary processor (the CPU). Operations performed by the coprocessor may be floating-point arithmetic, graphics, signal processing, string processing, cryptography or I ...
.
The Z320 was the
CMOS
Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss", ) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSF ...
version of the Z80000.
Linear vs. Segmented Addressing
Linear addresses used the complete result of any address computations, and so could address any part of memory without restriction.
Segmented addresses restrict effective address computations to the specified segment of the base pointer register. For example, if RR2 contained the value 0x10002000 (byte offset 0x2000 of small segment 4096), and you wanted to access a byte offset 0xE000 from this pointer, the final effective address would be 0x10000000, as the wrap-around into higher address bits is prevented. Base address bit 31 selects whether 64KiB segments (0) or 16MiB segments (1) are used. Note that the base address register (''not'' index registers!) determines the segment size and number.
''Segment'' in this case refers not to an Intel-style segment, but to a Unix-style segment.