Motherboard Memory Limitations 13
digitalunity asks:
"When most motherboards with room for 3 DIMMs state their
maximum memory as 768MB, it would seem that this is based
upon the assumption that a 256MB DIMM is the largest
available. I noticed that IBM has said that 1GB DIMMs will
be available soon. Are the stated memory limitations of motherboards
inherent to their design or can you really put more memory
than they state?"
How would they test 'em ?? (Score:1)
Re:How would they test 'em ?? (Score:2)
The engineers who design the motherboard can make pretty educated guesses as to what the electrical performance required at the socket will be for these parts. As long as the mechanical interface doesn't change and the electrical interface either sticks with preliminary information or doesn't change much from existing implementations they're in good shape. They protect themselves with the disclaimer: If the external manufactures don't make say a 1 gigabyte SDRAM with the projected specifications you can't sue then as it was just a best effort attempt.
BIOS limitations as well.... (Score:1)
I personally haven't seen any Intel-based mobo's that will accept anything over 256MB modules.
Memory and cache limits (Score:1)
Effective limits can be less than this, though - the Klamath core (most PIIs = 333, some 300's, a very few 266's, plus Celeron 266s and 300s) and Mendocino (Celeron A's) cores can cache 4gb. Not sure about the Xeons but they'll be at least 4gb.
Re:Memory and cache limits (Score:1)
I meant that PII CPUs at 333 or greater are Deschutes core (cache 4gb), most at 300 or below are Klamath (cache 512mb) but there are a few PII 300s and a very few PII 266s that use the Deschutes core. Celeron 266's and 300's also use the Deschutes core, Celeron A's use the Mendocino core which also caches 4gb.
Re:SEVERAL FACTORS TO CONSIDER (Score:1)
The implication of this, of course, is that more than 4 GB of memory will be useful only if you have several processes that want a lot of physical memory, as an individual process is never going to use more than 4 GB without segmentation support.
cjs
Re:SEVERAL FACTORS TO CONSIDER (Score:1)
cjs
Max Cacheable and registered memory (Score:1)
Also, alot of motherboards require you to use registered memory for modules that are 256MB or bigger. This may depend on the chipset and BIOS as well though.
What about the SS7 mobos? (Score:1)
Cacheing limitations? (Score:1)
Tell a man that there are 400 Billion stars and he'll believe you
SEVERAL FACTORS TO CONSIDER (Score:1)
maximum ammount or RAM that can be plugged
into a given MB
1. PCIset
Modern desktop chipsets are not built for
memory hungry applications. The phisical limit
is
-82440 LX: 512 MB SDRAM or 1 GB EDO
-82440 BX: 1 GB SDRAM
-82440 GX: 2 GB SDRAM (Using registered modules)
And for the server Chipsets
-82450 GX: 4 GB FPM
-82450 NX: 8 GB EDO
On a 32 bit plataform, it is doubtfull if it
makes any sense to have more than 4 GB, as this
forces the os and apps that mght want to use
it to do some segment translation (remember that
the P6 architecure implememnts a 36 bit adressing
mode)
I don't know if any modern OS supports them, however.
Regards
Roberto
Re:SEVERAL FACTORS TO CONSIDER (Score:1)
Which would be great for server apps but not
very charming for doing large simulations or
database work. BTW, i wonder if the problem
of relocating real 32 bit adresser under a
> 32 bit plataform (as requiered to talk
with 32 bit pci devices taht do bus mastering)
would be much of a problem. I wonder if
the people that has worked on NetBSD/Alpha
has got a look into it. Perhaps the "bounce buffers" from the ISA days might come back
(as ther are still very few 64 bit PCI cards)
Regards
ROBERTO
BTW, Have wou NETBSDers discusser if it would be
worthwile to implement a PSE36 port
I remember Alan Cox sayng it was a no-no