Why 400mhz DDR2 Ram

Hi guys,
I was little amazed today, while going through the specs of my order for I6000D. It read: 512MB, DDR2,400MHz 2 Dimms, Inspiron 6000.

Isn't the DDR2 ram supposed to be capable of running at 500mhz FSB for the 730 -1.6ghz(Sonoma)?

How about other guys..can you confirm your Ram speed?

Thanks

-Mad

 

533mhz rather.

-Mad

 

To my surprise , and the surprise of a few onthers on the net, the memory shipping with the inspiron 6000 as of 3/3/05 is DDR2 400mhz instead of the 533mhz that intel states the new chipset supports. 533 vs 400mhz is ~33% performance difference. Seeing how the ATIx300 needs a fast mem bus this is important. Dell's Memory guide says Mem Freq "400-533", and the prod page advertises 533 all over the place, but dosen't state that I can later add 533mhz mem.

A Dell sales-manager (i skipped over my rep) asked a Dell Tech who quickly said that it looks like all parts of the sys should support the 533 but the tech wouldn't give a set in stone awns at the time, but the manager says most likely. I'd like the opinion of the tech to be concrete.

Q: If I buy this will I be able to stick in DDR2-533mhz chips later?


Inspiron [email protected]
1GB DDR2 @400(wanted 533)
60gb 7200rpm HD
ATIx300 128MB
WUXGA 15.4" screen
DVD+- dual-layer
Intel a/b/g & Dell Bluetooth

 

I ordered mine with just 256mb and then ordered 2 x 512mb 533mhz pc2-4200 memory from crucial. The Crucial tech said that even if the i6000 did not utilize the 533mhz it would still operate at 400mhz. if it does not I will just exchange for the 400mhz pc2-3200 memory.

I should have the memory tomorrow but it looks like the i6000 is delayed for at least another week maybe more.

 

I've been researching this a bit.

A table in Tom's Hardware's Intel Sonoma 915 chipset review, specifically on

http://www.tomshardware.com/mobile/20050119/sonoma_alviso-07.html

seems to indicate the Intel 915 chipset supports DDRII-533 only in dual
channel configuration. Further, comments in the first paragraph of

http://www.tomshardware.com/mobile/20050119/sonoma_alviso-04.html

indicate some of these chipsets may not support dual-channel operation at all.

If these two facts are correct, it seems such a chipset would
have an effective 400MHz limit on DDR/II speed?

I left feedback on this to the authors of the review, but wouldn't expect a reply soon, if at all.

How do you all read this?

twice two makes five is sometimes a very charming thing too

 

Wow is this memory issue confusing.

Here is another related link on Toms to look at.
http://www6.tomshardware.com/mobile/20050119/sonoma_alviso-03.html

From this page I get the following, tell me if I am wrong.

With a system that is running dedicated graphics (x300 in the case of the i6000d).

Frontsidebus = 133 MHz x 4 (QDR) x 8 bit (64Bit) = 4.2 GB/sec

Memory =
4.2 GB/sec Single Channel DDRII-533
8.5 GB/sec Dual Channel DDRII-533

I don't know if the i6000d has dual channel enabled but these numbers imply that even if it does not the DDRII-533 memory running in single channel mode is fast enough (4.2 GB/sec) to keep up with the FSB speed which is also 4.2 GB/sec. Dual channel operation would not help since the speed is limited by the FSB to be 4.2 GB/sec.

So if the system is using slower DDRII-400 3.2 GB/Sec memory it would seem the memory is slower than the FSB so now the memory might become the limiting factor and system slows down to 3.2 GB/Sec even though the FSB is 4.2 GB/Sec.

However what is not clear is that if the i6000d is enabled for Dual channel operation then that same DDRII-400 memory may not be a limiting factor after all.

So if the i6000d is not dual channel enabled then the faster memory would make a difference. If it is dual channel enabled then the faster memory may not make a difference. Either way I think if the 533mhz memory works then the system would be running at 4.2 GB/Sec which is optimal. If you use the slower 400 mhz 3.2 GB/sec memory then the system may not be running optimal. Unless the i6000 is dual channel enabled which may make the memory issue moot. But that I am not sure about. i think the safe approach is to use the faster memory to assure it is running at 4.2 Gb/Sec which is the FSB speed.

Also, even if the i6000d is dual channel enabled, if you are running only one sodimm or two sodimm that are different in anyway. Then the system is not running dual channel mode and the 400mhz memeory would seem to hurt system performance.

They also go on to say, The situation is different for systems running integrated video.
The situation is different when we consider an integrated graphics core. In that case, an insignificant part of the memory bandwidth is "spent" on processing screen content. The graphics core dynamically allocates, depending on the settings in the BIOS system and drivers, up to 224 MB of RAM for the processing of video data. In this case, based on calculations alone, dual-channel operation with doubled maximum bandwidth of 8.5 MB/s makes sense.






On Ordered:
Inspiron 6000d
PM 760(2.0GHz)
15.4" WSXGA+
1 GB RAM (pc2-4200 533mhz from crucial, hope it works)
64MB ATI X300
60GB 7,200 RPM
CDRW/DVD
Bluetooth
2200
XP pro

 

Does this convince anyone?

In the I6000 Service Manual:
http://support.dell.com/support/edocs/systems/ins6000/sm/upgrades.htm#wp999869

Under the "Memory Module" section, it mentions TWICE, once under "Removing a Memory Module" and again under "Replacing a Memory Module":

NOTE: To get maximum performancedual-channel memory bandwidth capability, both memory module connectors must contain memory modules and the modules must be of the same size and configuration.

So this seems to indicate the I6000 indeed is set up for dual-channel operation.

That leaves the DDR speed vs. FSB speed issue, which I believe Steve explained correctly (other than accidentally swapping "Dual" and "Single" in his memory bandwidth option list).

I would add that DDRII-400 can be run in dual-channel mode as well, and should thereby give 3.2GB/sec x 2 = 6.4GB/sec transfer rate.

Thus, it would seem, with the 533MHz FSB as the upper limit:

A) If integrated graphics is in use, it would seem the dual-channel bandwidth is desirable, requiring paired SODIMMS.

B) With dual-channel bandwidth enabled, however, either the DDRII-400 (6.4GB/sec) or DDRII-533 (8.5GB/sec) should provide excess bandwidth beyond the FSB's 4.2GB/sec to serve the graphics core.

C) With single-channel only (i.e. only one or mismatched SODIMMS), DDRII-533 would be necessary to keep up with the FSB, and this only when dedicated graphics (with its own video RAM) is present so system memory is not shared.

DDRII-400 will only be sufficient for the processor's 533MHz FSB when configured to allow dual-channel operation -- i.e. in matched pairs of SODIMMs.

DDRII-533 in any configuration should meet or exceed the upper limit of the processor's needs with dedicated graphics present. Otherwise, dual-channel will be desired regardless of the faster speed over the DDRII-400.

Did I get this right?

twice two makes five is sometimes a very charming thing too

 

Steven:

Are you interested to sell your original 256 stick from Dell? Let me know.

 

It's a bit more complicated than that even. DDR2 has higher latency than DDR, which translates into poorer performance. This is the reason why the Sonoma doesn't seem to perform much faster than the older Centrinos with 333mhz fsb -- DDR's latency is much lower than the 4-4-4 timing of the first gen DDR2s - which basically KILLED its performance advantage.

I'll be getting my I9300 soon, will have to verify what timing the memory is running at in those -- if someone already have a 9300 can they do a quick check on the RAMs?

cheers,

yass

<blockquote id='quote'> quote:<hr height='1' noshade id='quote'>Originally posted by servano

 

<blockquote id='quote'> quote:<hr height='1' noshade id='quote'>Originally posted by timtop

 

<blockquote id='quote'> quote:<hr height='1' noshade id='quote'>Originally posted by Steven

 

<blockquote id='quote'> quote:<hr height='1' noshade id='quote'>
Did you get the 6000 yet? Is it confirmed that it handles the 533?
<hr height='1' noshade id='quote'></font id='quote'></blockquote id='quote'>

Yes, the 533mhz memory works in the 6000d.


Inspiron 6000d
PM 760(2.0GHz)
15.4" WSXGA+
1 GB RAM (pc2-4200 533mhz from crucial, it works)
64MB ATI X300
60GB 7,200 RPM
CDRW/DVD
Bluetooth
2200
XP pro

 

Looks like Inspiron 6000 memory is Dual Channel..

http://www1.us.dell.com/content/learnmore/learnmore.aspx?c=us&cs=04&l=en&s=bsd&~id=memory&~line=notebooks&~mode=popup&~series=inspn&~tab=details