ram 800mhz can to work at 533mhz cause cpu?

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One memory ram ddr2 800mhz on board (asrock) fsb 1000 and with support dual
channel ddr2 800/667/533 , I see in the bios that ram is at 533mhz:
Is a problem of bios setting? how resolve?
the value is correct?
the shop's technical said this limit is so becuse is the limit of the cpu
(amd sempron 2800 socket am2).

I not think but no sure;

Re: ram 800mhz can to work at 533mhz cause cpu?

de wrote:
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When you first start up a motherboard, and have not set up the BIOS,
the BIOS uses [Auto] for the memory. The BIOS reads the SPD chip
on the DIMM. It is the tiny 8 pin chip in the upper right hand corner
of these DIMMs.


If the SPD chip says "DDR2-533", then that is the value that the
BIOS will use. You can modify the value in the BIOS, by setting
the memory to [Manual]. Then select a speed for the memory.

The following information, is if you are interested in verifying
whether the memory you bought, is truly rated for DDR2-800 or not.

If you want to verify the contents of the SPD chip on the DIMM,
then CPUZ ( www.cpuid.com/cpuz.php ) can dump the information for you.
There is an option to dump info about your hardware in that program.
This message is an example of the information dumped. The two
hexidecimal tables at the end of this message, are the contents of
two DIMMs.


Using a copy of the JEDEC spec, you can decode the contents of the SPD.
Likely it says DDR2-533, and that is why the BIOS selected that

In terms of the real memory specification, if there are numbers
printed on the memory chip, you can tell what speed grade of
memory chip was used. This is an example of a DDR2 datasheet,
and there is a table that explains how the speed grade is
determined from the part number.


Page 7 of that document, shows the various speed grades. The
-5E is DDR2-400, and the -25E is DDR2-800. The number is the
clock period in nanoseconds, and the inverse of 5 nanoseconds
is 200MHz. That is doubled to get the DDR2-400 number. So, if
the memory chips on your DIMM have part numbers similar to
the Micron part, you can tell whether you have a genuine DDR2-800
DIMM or not. The -25 would suggest real DDR2-800 chips.

If the ICs used on the DIMM are blanks (nothing printed on them),
and the SPD contains bogus information (so the motherboard can
start properly), then there is no way to verify you have
genuine DDR2-800 memory. All you have is the sticker on the

On the processor end of things, you have a Sempron 2800+.


The core clock is 1600MHz, the input clock to the CPU is 200MHz,
which means the multiplier is x8.

You can look at the table for x8 multiplier here:


The first row of any table, is used when the CPU clock is at
its nominal value of 200MHz. In the following, the left hand
value is the value you set in the BIOS, and the right hand
value is the hardware clock rate of the RAM. This is what
happens when your Sempron is fed a 200Mhz nominal clock.

BIOS        Real_Speed
DDR2-400    400
DDR2-533    533
DDR2-667    640
DDR2-800    640

Due to your processor selection, I think that means the RAM
can run at a real speed of DDR2-640. This is due to the
memory divider limitation inside the processor. The processor
generates the clock signal to the memory, and the logic
inside the processor decides the "Real_Speed" value.

Now, if you choose to overclock the processor, then when the
processor is overclocked by 25% (from 200MHz input clock to
250MHz), then you have the option of running the memory
at a true DDR2-800 rate.

If you had selected a processor with a different multiplier
like x10, then the memory would have given true DDR2-800
speed when DDR2-800 was specified in the BIOS. Look at
the first line of the x10 table, to see the values.

This would be an example of a processor that can run the
memory at full speed, when the CPU is not overclocked.
This processor is 200x10 = 2000MHz, and uses the x10
table of numbers.


In conclusion, you can enter the BIOS, select [Manual] for
the memory. When you select a speed of DDR2-800 in the
BIOS, the memory will actually be running at DDR2-640.
I think that is the best you can do, until you overclock
the processor.


Re: ram 800mhz can to work at 533mhz cause cpu?

Quoted text here. Click to load it

If this said thai is 533, is or not 533?
Why the constructor not insert the really value in the
SPD chip?

Re: ram 800mhz can to work at 533mhz cause cpu?

de wrote:
Quoted text here. Click to load it

The contents of the SPD are a balance between technical correctness
and practical settings. If the SPD contained the value "DDR2-800",
then there are some motherboards that would not start up properly.
Some DIMMs are programmed with a lower value, to guarantee that the
motherboard will start. In cases where a lower value is stated in the
SPD, the user can set the desired value manually in the BIOS. If
the motherboard is a cheap uATX board, intended for business use,
in fact there might not be any way to set up the memory properly
in that case.

The SPD chip is programmed at the DIMM factory. The SPD chip is
typically a fixed device (likely OTP or one-time-programmable).
While in the past, it was possible to reprogram the SPD chip,
you will find recent products are less flexible in this
respect. For example, some old Macintosh computers, had the
ability to reprogram the SPD chip, but the SPD chip must
be the reprogrammable kind for that to work. The SPD chips
used now seem to be the fixed kind, and cannot be changed
by your system builder or by you. Only a BIOS setting can
correct any problems.

To give you an example, I have some Crucial memory. I have
four sticks of DDR400 memory. Each memory DIMM has a custom
serial number recorded inside it. That means Crucial programmed
the SPD chip, as part of the manufacturing process, and
assigned a unique serial number to every DIMM. There are
also memory products, where each DIMM has the same serial
number. For those DIMMs, the SPD chips come to the DIMM factory
in a big barrel, and the SPD chips all contain exactly the
same bit pattern. What it means for that manufacturer, is
if there are warranty returns to the factory, there is no
way to verify electronically, what the serial number of
the memory is. For those (cheap) manufacturers using
pre-programmed SPD chips, it means they are relying on the
sticker still being on the DIMM, to identify their product.

If you use the CPUZ program, and find the small hex table
of values I showed you in the dump file, I can decode the
parameters for you. Or you can do it yourself, with this.
The table of data, is a maximum of 256 bytes:



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