bnmohan via HWKB.com wrote:
> Does PC-133 SDRAM imply unbuffered 3.3V, or does PC-133 come in both buffered
> and unbuffered; and 3.3V and 5V
>
> Mohan
>
Example of PC133 registered RAM.
http://download.micron.com/pdf/datas...64_128x72D.pdf
Example of PC133 unbuffered RAM.
http://download.micron.com/pdf/datas...16_32x64AG.pdf
The example registered DIMM (RDIMM) has 9 memory chips on a side, for an array width
of 72 bits. That allows for ECC protection. There are three additional chips,
including a PLL clock buffer and register chips.
The unbuffered RAM in the example above, has 8 memory chips on a side. But
it is also available in an ECC configuration, with 9 memory chips on a side.
The distinction, is there is no PLL clock buffer and register chips, so the
module can be lower profile. The acronym that Micron uses for this is UDIMM,
which may also be a JEDEC term, but the RDIMM/UDIMM thing is not that popular
in retail advertising. Mainly because it might become confused with RIMMs or
RDRAM (RAMBUS technologies).
Of the four possible combinations, these are the types of memory you can buy
Registered with ECC (72 bit wide memory interface, same pin count)
Unbuffered with no ECC (64 bit wide memory interface, same pin count)
Unbuffered with ECC (72 bit wide memory interface, same pin count)
Registered with no ECC <------ Does not exist, server owner would not use.
The RAM above, all runs at 3.3V.
Voltage versus technology, from most recent to oldest. This is just going
from memory, and I'd have to dig through my junk pile to find the FPM/EDO
and verify the pin count.
1.5V DDR3 240pin
1.8V DDR2 240pin
2.5V DDR 184pin
3.3V SDRAM 168pin
5V FPM/EDO 72pin (asynchronous memory, no clock signal,
dampered, buffered, unbuffered)
More info can be found on Wikipedia
http://en.wikipedia.org/wiki/Dynamic..._access_memory
Paul
Pc133 buffered or unbuffered 
Linear Mode
