On the following pages:
The most used modern RAM type, SDRAM is made in 64 bit
wide modules called DIMMs (Dual Inline Memory Module).
They have a 168 pin edge connector. Here you see one module:
Since the DIMM modules are 64 bits wide, you can install one module at a time. They are available in 8, 16, 32, 64, 128, 256 MB, and 512MB with 6, 8, 10, and 12 ns speed. There are usually 2 -4 DIMM sockets on a motherboard.
The advantage of SDRAM is increased speed. That allows you to increase system bus speed. With 60 ns EDO-RAM, you can run at a maximum of 75 MHz on the system bus, while SDRAM speed can increase to 133 MHz and above. Also the SDRAM work synchronous with the system bus for a better performance.
Most chip sets are made for SDRAM. Some motherboards had both SIMM and DIMM sockets. The idea was that you could reuse old EDO RAM in the SIMM sockets, or choose to install SDRAM in the DIMM sockets. They were not designed to mix RAM types although it works at some boards.
Above: a 64 MB DIMM-module holding 32 chips each of 16 Mbit (32 X 16 Mbit / 8 bit = 64 MB).
It is better to use DIMMs made of the new 64 Mbit chips. A 64 MB module is this way made of only 8 chips (8 X 64 Mbit / 8 bit = 64 MB).
Intel have managed to speed up the processors power by factor 200 times the last ten years. That is a lot, but it is a problem that RAM memory technology only has improved by factor 20 in the same period.
Today we hope and dream of new fast RAM types, that will help us to get the full potential from our powerful PCs.
You can find a program, that tests the contents of the SPD at this c't homepage. It works with the Intel chip sets holding a 82371 south bridge like BX and GX.
VIA supports the PC133 RAM with their Apollo Pro Plus chip set (693A). Later they launched support for PC266 DDR RAM!
Also AMD's K7 Athlon may use PC133 RAM with the VIA KX133Pro chipset.
For a period of 12 months in 1999-2000, Intel experienced several disastrous incidents from their attempt to implement Rambus in chip sets and motherboards. During this period they were forced (by taiwanese motherboard manufactures) to adapt the PC133 standard.
The chip set i815 was the result of this revision of strategies.
Intel's problem is that they have "sold their soul" to Rambus Inc. According to their agreement, until 2003 Intel can only implement other RAM types than RDRAM if the bandwidth is less than 1 GB/sec. This agreement does not include server chipsets, from what we understand.
Read module 5a about expansion cards, where we evaluate the I/O buses from the port side.
Copyright (c) 1996-2005 by Michael B. Karbo. www.karbosguide.com.