How is RDRAM different from SDRAM

RDRAM - Rambus DRAM

The Rambus DRAM existed as early as 1995. The company Silicon Graphics used the RDRAM in their workstations. This memory was also used in Nintendo game consoles and on some graphics cards. At the end of 1996 the companies Intel and Rambus signed a license agreement. In order to enforce a monopoly on chipsets for the Pentium processors, Intel decided to only support this memory in its chipsets. Since the memory was very expensive due to the licensing policy, it never really caught on. At some point Intel also developed chipsets for SDRAM.

Storage architecture


As the name Rambus suggests, the RDRAM is a bus that is 16 bits wide. Here's the catch. Because despite the 400 MHz clock frequency and DDR process, the end of the line is quickly reached in terms of transmission rates. In comparison, SDRAM transmits four times as much data per clock with 64 bits. Furthermore, the RDRAM memory modules (RIMM) must always be plugged into the motherboard in a double pack. The Rambus memory modules are arranged one behind the other. The memory is accessed like a bus. With clock frequencies of 400 MHz, synchronous signal propagation times are necessary on all conductor tracks.
A functioning RAM bus storage system requires a closed bus and conductors of the same length from the storage to the storage controller. So that the conductor tracks are of the same length, this leads to unusual conductor track structures in a zigzag course on the motherboard.

RIMM - Rambus Inline Memory Module

The Rambus DRAM memory technology from Rambus is used on the RIMM modules. Since the Rambus interface is a bus interface and the memory modules are arranged one behind the other, unused slots must be filled with a dummy module, the C-RIMM. The C-RIMMs are modules without memory chips. They bridge unused slots that would otherwise lead to an open end of the Rambus bus.
RIMM modules can be easily identified through the heat sink. The sheet metal is necessary because the memory addresses are close together when accessing the memory. This leads to a higher load and extremely hot chips.
A special RIMM design (SO-RIMM, Small Outline RIMM) has been developed for notebooks and other portable computers.

XDR DRAM

The company Rambus, known as the licensor for Direct-Rambus-DRAM (RDRAM), has developed the memory technology XDR-DRAM. Sony uses XDR-DRAM in the Playstation 3.
As with normal DRAMs, the individual XDR chips communicate with the XDR I / O Cell (XIO). This can be anchored in the chipset or in the processor. The XIO has 8 to 32 data lines. XDR DRAMs have 8 or 16 data lines. The memory interface can transfer up to 6.4 GByte / s.
Special compensation and signaling techniques make the high-precision conductor tracks known from RDRAM unnecessary. Four-layer circuit board material is also sufficient for the memory modules. A memory expansion of 8 GB can be addressed with 12 address lines.

XDIMM

Memory modules with XDRDRAM are known as XDIMMs. XDIMMs have the same form factor and size as DDR2 DIMMs.

Overview: semiconductor memory

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Everything you need to know about computer technology.

Computer technology primer

The computer technology primer is a book about the basics of computer technology, processor technology, semiconductor memories, interfaces, data storage devices, drives and important hardware components.

I want that!