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18th September 2007 07:54 #1
512MB RAM DDR PC2100 . 1GB DDR PC3200 . , ? - ?
iPad | iPod | iPhone |iSiktir bee
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18th September 2007 08:18 #2
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18th September 2007 10:51 #3Registered User
Join Date: Sep:2007
Location: Bulgaria
Posts: 20
! . . . , , . ? 256MB PC2700 DDR SDRAM. verest . , ? , .
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18th September 2007 13:58 #4
DDR , .. PC3200 (400mhz) PC2700 (333mhz), - , .. 333mhz.
( '') high low density. low density , high density 10%.
high density . .
ECC non-ECC , , buffered unbuffered . .
, .
high / low density :
Keep in mind this explanation is for non-ECC modules, while the one I give below based on Wkipedia is for ECC modules - the bits per rank are different, i.e. 64 for non-ECC and 72 for ECC!
======================================== ========
"Standard' RAM chips are organized a DEPTH x 8 Bits. E.g. 32x8, 64x8,
etc. That means 8 of the chips make up a 64 bit wide rank (memory bus
is 64 bits wide). "Double Sided" is an old term to describe a stick
with 16 chips, 8 on each side. And with DEPTH x 8 chips that makes for
2 ranks (or, again in an older style terminology: 2 'banks').
'High Density' chips are DEPTH x 4 bits so it takes 16 to make a 64
bit wide memory rank. And this is why "double sided" is no longer the
favored description because when x8 chips are used "Double sided"
means "double rank" but with x4 chips it takes both sides and 16 chips
to make the ONE, single, rank.
Now to the problem. A memory 'slot' is usually designed for 'standard'
x8 chips and memory sticks containing 2 ranks. That is how the
'capacity' will be described. I.E. the K7S5A says it can handle up to
"1 gig" with two DDR slots, and that means 512Meg per slot, which
means 256 Meg PER RANK. (2 ranks per slot, 2 slots, etc)
But a 'high density' memory stick crams the 512 Meg into ONE RANK by
using 16 deeper (twice as deep) x4 bit width chips. And this is how
they arrive at the confusing term 'high density'. The chips themselves
are no higher in density than the x8 chips but since they are
organized as x4 they can cram more 'bytes' into a single rank because
16 chips make up a rank rather than 8, not that it helps make the
stick itself any 'higher' in 'density' because you can still only get
16 chips mounted on the thing.
So, a 512 Meg 'high density' stick puts 512 Meg in ONE RANK and a
'standard' density 512 Meg stick is two 256 Meg Ranks. Same size, same
'density'. It's the RANK organization that's different.
Since the memory slot on a K7S5A is two 256 Meg Ranks, a standard
density 512 Meg stick will work but a 'high density' 512 Meg stick
will not.
However, a 'high density' 256 Meg stick probably will since it crams
the 256 Meg into ONE RANK and the K7S5A can handle 256 Meg ranks.
For example, I'm running SDRAM on my K7S5A and, as it turns out, one
is 'standard' x8 density and the other is 'high density x4. But
they're both 256 Meg sticks and they both work. Damn irritating,
however, as they were both bought at the same time inside the same
package label, and same part number, with 16 chips on each so they
look identical (Kingston) but they are NOT the same thing. Doesn't
matter to my K7S5A but it means I can not use the 'high density' one
in my other motherboards because they support 128 Meg ranks (256 Meg
per slot but NOT in 'high density').
So, in a nutshell, if you're looking for 512 Meg sticks, make sure the
spec says they use x8 chips. But, if you're not trying to get 1 gig
then two 256 meg 'high density' sticks will be cheaper."
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Also check the example table near the bottom of this page: http://en.wikipedia.org/wiki/DDR_SDRAM
Example: Variations of 1 GiB PC2100 Registered DDR SDRAM module
Some explanations on the table:
They use 1GB module of ECC memory as example. The number of chips in ECC is multiple of 9, e.g. 36 or 18 chips in the whole module. For non-ECC the multiple is 8, e.g.. 16 chips.
The first three columns give the number of chips in module X the individual chip size, e.g. 36 x 256Mibit (divide 256 to 8 to get MiB, i.e. 256/8 = 32 MiB) = 1GiB (i.e. 36 chips x 32 MiB)
Now the last two colums. Keep in mind that DDR memory bus width per channel is 64 bits (72 for ECC memory).
Take the first row for example: 64M is a number of storage units (64 million), x4 (pronounced by 4) number of bits per chip. 4 bits per chip X 36 chips in module = 144 bits (distributed in 2 rows/ranks it makes exactly 72 bits per rank for ECC memory).
Don't let the numbers 64M and 128M confuse you. They are only the number of storage units in millions and are not used in the calculations.
Now you need to know what memory density does you motherboard support in order to make the right decision about buying memory..
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18th September 2007 20:02 #5
oldschool
, - , - , . : - 512- 1 ? , - - ( - ). ( ) - -. ?iPad | iPod | iPhone |iSiktir bee
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18th September 2007 20:19 #6
, Everest.
D80; 50/1.8D; Tamron 70-300; 18-55 VR;
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19th September 2007 16:29 #7




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