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The first PC motherboards with support for RDRAM debuted in 1999. They
supported PC-800 RDRAM, which operated at 400 MHz and delivered 1600 MB/s of
bandwidth over a 16-bit bus. It was packaged as a 184-pin RIMM (Rambus
in-line memory module) form factor, similar to a DIMM (dual in-line memory
module). Data is transferred on both the rising and falling edges of the
clock signal, a technique known as double data rate. For marketing reasons
the physical clock rate was multiplied by two (because of the DDR
operation); therefore, the 400 MHz Rambus standard was named PC-800. This
was significantly faster than the previous standard, PC-133 SDRAM, which
operated at 133 MHz and delivered 1066 MB/s of bandwidth over a 64-bit bus
using a 168-pin DIMM form factor
Moreover, if a mainboard has a dual- or quad-channel memory subsystem, all
of the memory channels must be upgraded simultaneously. 16-bit modules
provide one channel of memory, while 32-bit modules provide two channels.
Therefore, a dual channel mainboard accepting 16-bit modules must have RIMMs
added or removed in pairs. A dual channel mainboard accepting 32-bit modules
can have single RIMMs added or removed as well. Note that some of the later
32 bit modules had 232 pins as compared to the older 184 pin 16 bit modules.
Typical RDRAM clock rates are 266, 355, 400, 533, 600 and 800 MHz.
A 128Mb rambus ram
Found in the
HP Vectra VL800. |
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