64 – bit Processor
- The brain of the PC is processor or CPU.
- It performs the system’s calculating and processing operations.
- The term N-bits means that its ALU, internal registers and most of its instructions are designed to work with N-bit binary words.
- The major components of CPU are:
- 64-bit processors have 64-bit ALUs, 64-bit registers, and 64-bit buses.
- A 64-bit register can address up to 264 bytes of logical address.
- 64-bit processors have been with us since 1992.
- Eg: 64-bit AMD processor.
- The internal logic design of microprocessor which determines how and when various operations are performed.
- The various function performed by the microprocessor can be classified as:
- Microprocessor initiated operations
- Internal operations
- Peripheral operations
- Microprocessor initiated operations mainly deal with memory and I/O read and write operations.
- Internal operations determines how and what operations can be performed with the data.The operations include:
2. performing arithmetic and logical operations
3. test for conditions
4. store in the stack
- External initiated operations are initiated by the external devices to perform speci al operations like reset, interrupt, ready, etc.
- The block diagram of 64-bit microprocessor is shown below.
- The major parts of the block diagram are:
- General register unit
- Control and decoding unit
- Bus unit o Cache memory unit
- Floating point register unit
- Issue ports
- Addressing Modes
- General Purpose Registers
- Non-modal and modal Instructions
- New Instructions in Support of 64-bit
- New immediate Instructions
- This addressing mode determines the working environment. i.e 24,32 or 64 bit mode
- PSW bits 31 and 32 designate addressing mode (out of 64 bit).
- Addressing modes bits:00=24 bit-mode
General purposes register (GPR)
- The register is treated as 64-bits for:
- Address generation in 64-bit mode.
- The register is treated as 32-bits for:
- Address generation in 24/32-bit mode.
New instructions in 64-bit:
- Load Reversed - LRV, LRVR
- Multiply Logical - ML, MLR
- Divide Logical - DL, DLR
- Add Logical w/ Carry - ALC
- Subtract Logical w/ Borrow - SLB
- Store Reversed - STRV
- Rotate Left Single Logical – RLL
New immediate Instructions
- Load Logical Immediate
- Insert Logical Immediate
- AND Immediate
- OR Immediate
- Test Under Mask (High/Low)
Comparison of 64-bit with 32-bit
- Contains 32-bit data lines whereas 64-bit contains 64 data lines.
- Can address max 2^32(4 GB) of data whereas 64 bit can address 2^64(18 billion GB).
- Speed and execution is both fast in 64-bit processors.
- 64-bit processors can drive 32-bit applications even faster, by handling more data per clock cycle than a 32-bit processor.
- The table shows the basic difference between two:
- Previous processors can have max 4 Gb of physical memory but 64-bit can handle more.
- More general purpose registers than in older processors.
- Significant increase in speed due to wider data bus and processing is fast
- Compatibility difficulty with existing software as they are mostly developed to the 32-bit processors.
- 64-bit OS must have 64-bit drivers, for working efficiently.
- They are costly.