OT: Looking for PC133 RAM

[Lennart Sorensen]

On Wed, May 28, 2008 at 04:19:05PM -0400, D. Hugh Redelmeier wrote:
> I wish Crucial was that informative about the computer I'm trying to
> upgrade.
> 
> I find it annoying that it is rarely made clear what is required for
> PC100 / PC133 compatibility.  I often heard "PC133 memory won't work
> as a substitute for PC100" -- the answer is more complicated.  Speed
> should not be an issue but memory configuration can be.
> 
> The computer I'm playing with is a Dell Dimension XPS T450.  It has a
> BX chipset (old, for sure).
> 
> It came with a PC100 128M memory module.
> 
> It would not work with a PC133 256M module.  It did not even recognize
> the module (some systems recognize half of a module, but not this
> time).  That same module does work in a Dell Optiplex GX115 (i815
> chipset).

The maximum ram in that model is 768MB (3 x 256MB) and as a result that
means the 256MB modules have to be "double sided" which normally means 8
chips on each side of the DIMM.

The i815 supports twice as much, so 512MB modules as long as they have
16 chips, which is the same as my VIA KT133 board.

> Both modules have 8 RAM chips; both kinds of chips are 8 bits wide.
> Thus each chip is active in each (64-bit) memory cycle; I think that
> means that the modules are termed "single sided".

Correct, and it means your 440BX can't use it.

> Chips on working module: Toshiba TC 59SM708FT-80
> 	4M words x 8 bits x 4 banks
> 	http://datasheet.digchip.com/487/487-13062-0-TC59SM704FT.pdf
> 
> Chips on failing module: Micron Technology MT48LC32M8A2-75
> 	8M words x 8 bits x 4 banks
> 	http://download.micron.com/pdf/datasheets/dram/sdram/256MSDRAM.pdf
> 
> One possibly relevant difference: the working chips 4k rows to be
> refreshed every 64ms whereas the non-working ones have 8k rows to be
> refreshed in the same period.  On the other hand, if I read it
> correctly, the BX chipset can refresh as many as 8k rows (assuming the
> BIOS sets it up right).
> 	http://download.intel.com/design/chipsets/datashts/29063301.pdf

No, the 440BX can refresh 4k rows max.

> Can anyone explain what actually are the parameters that matter in
> PC100 and PC133 memory systems?

The 440BX supposet up to 128Mbit chips using 16Mx8.  So your 32Mx8
modules will not work.

-- 
Len Sorensen
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