Chapter 5 Internal Memory Pokok pokok penting Dua saluran dasar semikonduktor RAM Dynamic RAM (DRAM) Static RAM (SRAM) SRAM lebih cepat dan lebih mahal, (digunkan untuk cache memory) DRAM digunakan untuk main memory Digunakan teknik koreksi kesalahan pada sistem memori, dgn penambahan bit tambahan Untuk mengimbangi kecepatan yg relatif rendah dari DRAM beberapa organisasi DRAM diperkenalkan al: Synchronous DRAM (SDRAM), Rambus DRAM (RDRAM)

Chapter 5 Internal Memory Semiconductor Memory Types

Semiconductor Memory Pada Komputer generasi awal memori utama sering disebut dgn Core (inti), karena dibuat dari ferro-magnetis. RAM all semiconductor memory is random access Read/Write Volatile Temporary storage Static or dynamic

Semiconductor Memory Organisasi Elemen dasar : sel memori Sel memori memiliki sifat-sifat: Memiliki dua keadaan stabil semi-stabil untuk merepresentasikan bil biner 0 atau 1 Sel memori mempunyai kemampuan untuk ditulis (menetapkan keadaan) Sel memori mempunyai kemampuan untuk dibaca (membaca keadaan) Memiliki 3 terminal: Control (r atau w), Select dan Data in / sense

Memory Cell Operation

Dynamic RAM Bits stored as charge in capacitors Charges leak ( ada kebocoran shg lama-lama isi kapasitor bisa habis) Need refreshing even when powered Simpler construction Smaller per bit Less expensive Need refresh circuits Slower Main memory Sel DRAM merupakan perangkat analog, dan level muatan akan menentukan nilai logika 1 atau 0

Dynamic RAM Structure

DRAM Operation Address line active when bit read or written Transistor switch closed (current flows) Write Voltage to bit line High for 1 low for 0 Then signal address line Transfers charge to capacitor Read Address line selected transistor turns on Melalui bit line muatan kapasitor dibandingkan dengan nilai referensi untuk menentukan logika 0 atau 1 Capacitor charge must be restored

Static RAM Bits stored as on/off switches No charges to leak No refreshing needed More complex construction Larger per bit More expensive Does not need refresh circuits Faster Digunakan untuk Cache memory Rangkaian Digital : menggunakan flip-flops

Stating RAM Structure

Static RAM Operation Transistor arrangement gives stable logic state C1 high, C2 low T1 T4 off, T2 T3 on State 0 C2 high, C1 low T2 T3 off, T1 T4 on Address line transistors T5 T6 is switch Write – apply value to B & compliment to B Read – value is on line B

SRAM vs DRAM Both volatile Power needed to preserve data Dynamic cell Simpler to build, smaller More dense (lebih padat / banyak untuk ukuran luas yang sama dgn SRAM) Less expensive Needs refresh Larger memory units Static Faster Cache

Read Only Memory (ROM) Permanent storage Nonvolatile (tdk perlu sumber tegangan untuk menjaga data/nilai) Aplikasi penting dari ROM: Microprogramming (pada bab berikutnya) Library subroutines Systems programs (BIOS) Function tables ROM dibuat dlm IC: Pengisian data memerlukan biaya tetap besar (satu atau ribuan ) Tidak ada ruang untuk salah, Jika ada satu bit salah, maka seluruh keping ROM harus dibuang

Types of ROM Written during manufacture Programmable (once) Very expensive for small runs Programmable (once) PROM Untuk memprogram peralatan khusus. Read “mostly” Erasable Programmable (EPROM) Erased by UV Electrically Erasable (EEPROM) Waktu untuk write lebih lama dari read Flash memory Termasuk Semiconductor memory (diantara EPROM dan EEPROM) Data dpt dihapus per block, dgn electric 1 bit per Transistor dan dpt dihapus dengan single action =>Flash

Organisation in detail A 16Mbit chip can be organised as 1M of 16 bit words A bit per chip system has 16 lots of 1Mbit chip with bit 1 of each word in chip 1 and so on A 16Mbit chip can be organised as a 2048 x 2048 x 4bit array Reduces number of address pins Multiplex row address and column address 11 pins to address (211=2048) Adding one more pin doubles range of values

Refreshing Refresh circuit included on chip Memerlukan waktu Menghambat Kinerja

Typical 16 Mb DRAM (4M x 4) RAS = Row Address Select CAS = Column Address Select WE = Write Enable OE=Output Enable

Packaging

Module Organisation

Module Organisation (2)

Error Correction Hard Failure Soft Error Permanent defect (Cacat Permanen) Soft Error Random, non-destructive (tdk bersifat merusak) No permanent damage to memory Biasanya disebabkan oleh Power suppy, atau partikel-partikel alpha. Detected using Hamming error correcting code

Error Correcting Code Function Error Correction bit

Hamming Error – Correction code Parity Bit ditambah agar jumlah bit 1 genap 4 – bit Data Posisi bit yg error dpt diketahui Error Terjadi

Hamming Error – Correction code Contoh : Terjadi 2 bit yang error lihat hal 151 Untuk data lebih dari 4-bit (lihat di hal 148-150)

Advanced DRAM Organization Basic DRAM sama dengan RAM chips (saat awal) Enhanced DRAM Contains small SRAM SRAM holds last line read (c.f. Cache!) Cache DRAM Larger SRAM component Use as cache or serial buffer

Perbandingan Beberapa DRAM SDRAM : clock 166 MHz, Transfer rate 1.3GB/s, Access time 18 ns DDR DRAM: 200 MHz, 3.2GB/s, 12.5 ns RDRAM: 600 MHz, 4.8GB/s, 12 ns

Synchronous DRAM (SDRAM) Access is synchronized with an external clock Address is presented to RAM RAM finds data (CPU waits in conventional DRAM) Since SDRAM moves data in time with system clock, CPU knows when data will be ready CPU does not have to wait, it can do something else Burst mode allows SDRAM to set up stream of data and fire it out in block DDR-SDRAM sends data twice per clock cycle (leading & trailing edge)

IBM 64Mb SDRAM

SDRAM Operation

RAMBUS Dikembangkan oleh Rambus Adopted by Intel for Pentium & Itanium Main competitor to SDRAM Vertical package – all pins on one side Data exchange over 28 wires, < 12 cm long Bus addresses up to 320 RDRAM chips at 1.6 Gbps Asynchronous block protocol 480ns access time Then 1.6 Gbps

RAMBUS Diagram

Cache DRAM (CDRAM) Dikembangkan oleh Mitsubishi Mengintegrasikan cache SRAM kecil ke suatu keping DRAM yang umum.

Latihan Hamming Code Soal lihat dibuku hal 160

There are two main physical formats for memory: SIMMs - Single Inline Memory Modules, and DIMMs - Dual Inline Memory Modules SIMMs must be installed in pairs. So there will be either two or four SIMMs installed in their slots, never one or three. DIMMs on the other hand may be installed in any number

Memory is also called RAM, or Random Access Memory Memory is also called RAM, or Random Access Memory. The main types of RAM are: 1) FPDRAM - Fast Page Dynamic RAM, 2) EDO - Extended Data Out, and 3) SDRAM - Synchronous Dynamic RAM. Fast Page RAM is the original type of RAM used in computers up until the Pentium. Typical memory access time was 100 ns (nanoseconds). EDO RAM was introduced with the Pentium class of computers, but was short-lived. The advantage of EDO RAM was that it had faster read / write (access) times than Fast Page RAM. Typical access times were 70, 60, and 50 ns. The smaller the number, the faster the access time, and the more desirable it is for fast computing. Not all computers that use EDO RAM could use the same speed of EDO RAM. Some computers could only use 70 ns chips. SDRAM was introduced with the Pentium II and has the fastest memory access times at 9 nsec. The three types of RAM are not compatible with all motherboards. Each motherboard can only use one specified type of RAM. The amount of RAM on any given motherboard is limited by the motherboard's memory controller, which is specified by the manufacturer. Putting more RAM on a motherboard means that only the maximum amount of memory the motherboards can use will be used. The rest of the memory will not be used.