Kind of memory to a Pentium II-type box?

Jörg W Mittag Joerg.Mittag at Web.De
Mon Oct 25 04:34:16 PDT 2004


Uli Fahrenberg wrote:
> Miguel Bazdresch, Oct 25, 09:53 +0200:
>> I used to have a PII-233MHz (one of the very first ones; I think it 
>> had an intel 440BX chipset). I'm almost 100% sure that, as Kevin says, 
>> it used PC-100 SDRAM.
> I'm plugging in here as I have the same problem, only my PII-MMX in 
> question has only 32MB RAM. Not a lot if you want to run WinXP on it...

The installer will refuse to boot unless you have at least 64 MiByte of RAM
in there.

> So, question: Assuming the 32MB are PC-100 SDRAM, will PC-133 SDRAM 
> work, too?

As others have said, yes, theoretically it *should* work. There are some
caveats, though.

The first problem is that some module vendors aren't programming their
SPD-EEPROM (Serial Presence Detect, it contains among other things the
module vendor and, more importantly, the supported timings) correctly. A
PC133-222 module should at least be able to run in a 2-2-2 timing at 100
MHz, if not even better. However, some vendors simply "forget" to enter the
correct timing data for slower speeds into their SPD so that the module will
run with a 3-3-3 timing at 100 MHz. A workaround is to disable automatic
detection in the BIOS setup and enter the correct values manually. I don't
think that it's possible to reprogram the SPD-EEPROM in the field, so you're
stuck with whatever is in there.

A second problem, specifically with the Intel 440BX chipset mentioned in
this thread is that the number of address lines of the chipset is not
sufficient to drive big chips. The 440BX can only drive chips up to 128
MiBit and more specifically, only 128 MiBit chips in 16Mx8 organization. On
32Mix4 chips the chipset will only be able to address 16Mi, turning your
shiny new 128 MiByte PC133-SDRAM module built of 8 32Mix4 chips in a 64
MiByte module. So, if you want to buy a 128 MiByte or 256 MiByte module for
a 440BX chipset, you should make sure it has at least 8 (16) chips on it.
Another important point is that technically the 440BX can only drive 128
MiBit chips on buffered modules but unless you actually want to use all
memory slots it usually works with unbuffered modules. You don't have to
worry too much about the 32Mix4 chips, at least on unbuffered modules, since
they are pretty rare and have only seen wider deployment on buffered
modules.

Well, and the last problem is ... money. SDR-SDRAM tends to be way more
expensive than DDR-SDRAM these days. Especially so, since 128 MiBit chips
are extremely rare nowadays. I think the smallest chips built today are 256
MiBit chips, gradually being phased out for 512 MiBit chips. Today you will
probably not see more than 4 256 MiBit or even 2 512 MiBit chips on a 128
MiByte module, so you  will probably have to go for either used parts or
memory dealers spezialized on old memory (with specialist prices). Well,
usually they give compatibility guarantees, so the prices are actually fair,
but it's still a lot of money.

jwm
-- 
bbdb-2.35% ./configure
checking for my keys... not found
Damn! I'm locked outside :-(



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