multiple types of PC133 RAM?

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Hi all,
I'm trying to cobble together a frankencomputer out of two HP laptops
each suffering from various maladies.  One of them has 128 MB of RAM, a
PC133 SODIMM labeled:


while the other has 256 MB of RAM, a PC133 SODIMM labeled:


I can use both pieces of RAM successfully in the computer with the
PC133S RAM.  However, if I put both pieces in the computer with the
PC133U RAM, the 256MB of memory is completely corrupted, as confirmed
by the BIOS diagnostics or Linux memtest kernel.

Are there multiple incompatible types of PC133 RAM?  Is there any way I
can get the 256MB piece of RAM to work in the computer that currently
only has 128MB?


Dan Lenski

Re: multiple types of PC133 RAM?

Dan Lenski wrote:
Quoted text here. Click to load it


Product Label

The following label should be applied to all PC133-compatible SO-DIMMs,
to fully describe the key attributes of the module.


m: Module Type
    S = Unbuffered SO-DIMM (no registers or PLLs on SO-DIMM)
a: SDRAM CAS Latency
b: SDRAM minimum t RCD specification (in clocks)
c: SDRAM minimum t RP specification (in clocks)
dd: SDRAM t AC specification (into 30 pF load), with no decimal point
     54= 5.4 ns t AC
e: JEDEC SPD Encoding Level used on this SO-DIMM
    2 = JEDEC SPD Encoding Level 2.0
f: Gerber file used for this design (if applicable)
    A: Reference design for R/C ‘A’ is used for this assembly
    B: Reference design for R/C ‘B’ is used for this assembly
    Z: None of the ‘Reference’ designs were used on this assembly
g: Revision number of the reference design used:
    1: 1st revision (1st release)
    2: 2nd revision (2nd release)
    3: 3rd revision (3rd release)
    Blank: Not Applicable (used with ‘Z’ above)

is a PC133 Unbuffered SO-DIMM
with CL = 3, tRCD = 3, tRP = 3
and a t AC = 5.4 ns, using JEDEC SPD Encoding Level 2
and produced based on the ‘B’ raw card Gerber, 2nd release

There is a little info here. But not too useful.


Back on the JEDEC site, this doc has a table of package types.
PC133U implies Unbuffered DIMM, which should not be the same
form factor as PC133S (SODIMM, i.e. for laptop). Note that
this table could be specific to the topic they are discussing,
rather than generic. But so far, this is the best I can do
at finding a table of values. Forcing a user to go through one
doc after another to find the module type, is not very good.

m = Module Type
     E = Unbuffered DIMM ("UDIMM"), with ECC (x72 bit module data bus)
     F = Fully Buffered DIMM ("FB-DIMM")
     M = Micro-DIMM
     N = Mini-Registered DIMM ("Mini-RDIMM"), no address/command parity function
     P = Registered DIMM ("RDIMM"), with address/command parity function
     R = RDIMM, no address/command parity function
     S = Small Outline DIMM ("SO-DIMM")
     U = Unbuffered DIMM ("UDIMM"), no ECC (x64 bit module data bus)
     Y = Mini-Registered DIMM ("Mini-RDIMM"), with address/command parity

I checked my collection of spare modules, and I do have a
PC133U, and it is a DIMM and not an SODIMM.

The next step would be to examine the number of memory chips
on the module, and the part number printed on the chip. The
chip could have several lines of alphanumeric text printed on
it. One line should be a part number, another line a date
code and lot number, and so on. It may be possible to look the
chips up and figure out what you've got, that way.


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