Arsitektur Komputer
Pertemuan – 11
Mode Pengalamatan
© 2009 Fakultas Teknologi Informasi Universitas Budi Luhur
Jl. Ciledug Raya Petukangan Utara Jakarta Selatan 12260
Website: http://fti.bl.ac.id Email: sekretariat_fti@bl.ac.id
Mode Pengalamatan
Mode Pengalamatan
1. Immediate
2. Direct
3. Indirect
4. Register
5. Register Indirect
6. Displacement (Indexed)
7. Stack
Pengalamatan: Immediate
1. Operand adalah bagian dari instruksi
2. Operand = address field
e.g. ADD 5
3. Tambah 5 ke Isi Akumulator
4. 5 adalah operand
5. Tdk ada referensi memori utk fetch data
6. Cepat
7. Range Terbatas
Mode Pengalamatan
Format Instruksi : Immediate
Instruction
Opcode
Operand
Pengalamatan: Direct Addressing
1. Address field mengandung alamat o operand
2. Effective address (EA) = address field (A)
e.g. ADD A
3. Tambahkan isi A ke accumulator
4. Lihat address A sebagai operand
5. Single memory reference untuk akses data
6. Tak ada kalkulasi tambahan untuk effective address
7. Jangkauan Alamat terbatas
Mode Pengalamatan
Format Instruksi : Direct
Mode Pengalamatan
Pengalamatan: Indirect
1. Sel Memori ditunjuk oleh field alamat yang mengandung alamat operand
2. EA = (A)
Look in A, temukan alamat (A) dan cari operand
e.g. ADD (A)
Tambahkan isi dari sel yang ditunjuk dengan isi dai akumulator A
Format Instruksi: Indirect
Mode Pengalamatan
Pengalamatan: Register
1. Operand is held in register named in address filed
2. EA = R
3. Limited number of registers
4. Very small address field needed
5. Shorter instructions
6. Faster instruction fetch
Format Instruksi: Indirect
Mode Pengalamatan
Pengalamatan: Register Indirect
1. C.f. indirect addressing
2. EA = (R)
3. Operand is in memory cell pointed to by contents of register R
4. Large address space (2n)
5. One fewer memory access than indirect addressing
Format Instruksi: Reg. Indirect
Mode Pengalamatan
Pengalamatan: Displacement
1. EA = A + (R)
2. Address field hold two values
3. A = base value
4. R = register that holds displacement
5. or vice versa
Format
Instruksi: Reg. Indirect
Mode Pengalamatan
Pengalamatan: Relative
1. A version of displacement addressing
2. R = Program counter, PC
3. EA = A + (PC)
i.e. get operand from A cells from current location pointed to by PC
4. c.f locality of reference & cache usage
Pengalamatan: Base Register
1. A holds displacement
2. R holds pointer to base address
3. R may be explicit or implicit
4. e.g. segment registers in 80x86
Mode Pengalamatan
Pengalamatan: Indexed
1. A = base
2. R = displacement
3. EA = A + R
4. Good for accessing arrays
5. EA = A + R
6. R++
Pengalamatan: STACK
Operand is (implicitly) on top of stack
e.g. ADD Pop top two items from stack and add
Mode Pengalamatan
Pentium Addressing Mode
Virtual or effective address is offset into segment
Starting address plus offset gives linear address
This goes through page translation if paging enabled
addressing modes
1. Immediate
2. Register operand
3. Displacement
4. Base
5. Base with displacement
6. Scaled index with displacement
7. Base with index and displacement
8. Base scaled index with displacement
9. Relative
Mode Pengalamatan
PowerPC Addressing Mode
1. Load/store architecture
2. Indirect
Instruction includes 16 bit displacement to be added to base
register (may be GP register)
Can replace base register content with new address
3. Indirect indexed
Instruction references base register and index register (both may
be GP)
EA is sum of contents
4. Branch address
5. Absolute
6. Relative
7. Indirect
8. Arithmetic
Operands in registers or part of instruction
Floating point is register only
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PowerPC Memory Operand Addressing Modes
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Instruction Format PowerPC
Layout of bits in an instruction
Includes opcode
Includes (implicit or explicit) operand(s)
Usually more than one instruction
format in an instruction set
Instruction Length PowerPC
Affected by and affects:
Memory size
Memory organization
Bus structure
CPU complexity
CPU speed
Trade off between powerful instruction repertoire and
saving space
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Alokasi Bit PowerPC
Number of addressing modes
Number of operands
Register versus memory
Number of register sets
Address range
Address granularity
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Format Instruksi :PDP-8
Mode Pengalamatan
Format Instruksi : Pentium