Quick question RE: RAM Speed vs. Bus speed

[gbh]

Hi, new here. I'm fairly tech-savvy, but apparently not quite enough to answer this question with 100% certainty.

I have a Dell Precision T5400 Workstation. I work in a University Research Lab and am handling some very large datasets (1 file @ 7.8 GB, needing to crunch stats on it) that are currently maxing out the 8GB RAM on my system.

Current (basic) system specs:

Dell Precision T5400:

Proc:
- Dual Quad-Core Intel Xeon E5420 @ 2.5 GHz, 1.225V
- 4x32 KB L1 Data cache, 4x32 KB L1 Instruction cache (8-way) per chip
- 2x MB L2 Cache (24-way) per chip

Motherboard:
- Dell 0RW203 - A00
- Intel 5400A chipset, Rev. C0
- 332.5 MHz Bus, (x 7.5 multiplier) Rated FSB: 1329.9 MHz

Memory:
- 8192 MB (8x1GB DIMM) FB-DDR2 RAM
- 333MHz, 5-5-5-15 timings (in addition to size, I'm doubling speed w/ this upgrade... memory is the bottleneck)

Graphics:
- PCI-Express, x16
- NVidia Quadro FX 1700, 512 MB memory @ 460MHz (920 MHz shaders)
(not top-end, but I don't need a top-end graphics card, and it supports my dual 23" HD monitors just great.)

Storage:
- WD1001FALS SATA2, 1TB (data)
- WD2500AAJS SATA2, 250GB (OS & programs)

OS:
- Windows 7 Enterprise 64x (often w/ an Ubuntu 10 VMware image running atop)

Other random crap:
- 1 CD-DVD ROM ATA drive
- 1 DVD+/- RW ATA drive
- SoundMax Integrated Digital HD Audio chipset (which I care little about)
- Broadcom NetXTreme 57xx Gigabit Ethernet controller
- USB 2.0 drives, all the other random little stuff you'd expect.


I'm looking to upgrade the RAM to handle these large datasets without crashing my Stats program. The Dell Tech support guy said the fastest DDR2 RAM my system would support is 667 MHz, which is what most if it on the market is anyway, so that's what I'm looking for. I'm looking at 32 GB of 667MHz FB-DDR2 RAM (needs to be fully-buffered) that I'll probably order tomorrow, for $856. Not cheap, but cheaper than overhauling the whole motherboard/system to accommodate DDR3 RAM while maintaining 8 cores and up to 32GB RAM.

But CPU-Z tells me my current bus speed is 333 MHz, with a 7.5x multiplier making the FSB 1329.9 MHz. Neither of those figures matches the 667 MHz figure the tech-support guy said. So my question: Will my system only benefit from 333 MHz memory (i.e the max bus speed), or can it theoretically handle up to the FSB at 1.3 GHz? Or is there (likely) some variable I don't know about to put the cap at 667MHz?


For those of you more familiar with the ins & outs of RAM upgrades, can ya' help clarify? I've kinda reached the outer limit of my knowledge of this stuff. Thanks!

- Mike

 

[TheoneandonlyMrK]

im no expert on dual cpu systems but i do know that memory is often ran at different speeds to the fsb ,by use of a multiplier thats set in the bios menu for the cpu normally.
this can be usefull when overclocking to ensure stability by lowering the multiplier but you can also overclock the memory with it or generally choose its speed.

 

[Nailezs]

can you post a picture of your bios? specifically the screen showing voltages and frequencys

i think your misunderstanding what is what, and i'm a little rusty and can't recall what i want off hand lol

 

[gbh]

can you post a picture of your bios? specifically the screen showing voltages and frequencys

i think your misunderstanding what is what, and i'm a little rusty and can't recall what i want off hand lol

It's DELL BIOS revision A06, which I know isn't exactly what you asked for, but getting into the BIOS screen right now requires a reboot and I'm in the middle of a couple things, so I'll have to get that for ya' later.

You might be right (about me mixing something up), I'll try to get you what you need if it makes any difference.

 

[Nailezs]

ok. i'll take a look at some stuff tonight also

theres something i always thought was wierd about how ram speed is equated(?) and how it related to fsb. damnit, i could have told you it off-hand a year ago when i was OCing my system lol

 

[slyfox2151]

DDR2 is double data rate.... so you take your bus speed.... 333 and double is..... witch acutaly works out to be 667 not 666. thats how fast your ram can be.





Note* if you changed the ram devider in the bios you could make the ram run faster or slower then the bus speed.

 

[erixx]

I know its not the full answer, but your RAM at 333 equals to 666 when explained as DDR. Your processor or FSB is related but by a certain multiplier and divider, so no need to worry as long as your BIOS supports the RAM speed you are going to buy... !

Your link with the order says it: SPEED: DDR2-667 (333MHZ)

 

[Nailezs]

yeah, waht they said

wow, i feel soo stupid right now lol

 

[cdawall]

ram dividers allow the system to use different speed rams. Your system supports a max of 67 FBDIMMS but can also probably support 533mhz and 400mhz ones

667 is running 2:1 with the bus speed of 333
533 is running 5:4 with the bus speed of 333

its a dell he cant change the ram divider, its based off of bus speed not FSB which is quad pumped off of the 333mhz bus speed

 

[gbh]

Okay, cool. Thanks, all. I just checked the BIOS and it said the RAM was running 667MHz, not 333 (like CPU-Z told me the memory bus was running at), but y'all's explanation of that makes sense to me.

So, 667 is what I'll buy, that's what fits best, and it makes sense to me why now. Thank you all!

 

[JrRacinFan]

In addition, what you see by "1329.9 fsb" is in reality the effective speed of your northbridge, and is quad pumped(4x333) EDIT: I am a slow typer cdawall beat me to it LOL . It is related to ram clocks but not quite so much.

@cdawall

Your figures are on ddr3 specs, not ddr2. For ddr2 the proper ratios would be 667 is 1:1 and 533 is 4:3.

 

[cdawall]

In addition, what you see by "1329.9 fsb" is in reality the effective speed of your northbridge, and is quad pumped(4x333) EDIT: I am a slow typer cdawall beat me to it LOL . It is related to ram clocks but not quite so much.

@cdawall

Your figures are on ddr3 specs, not ddr2. For ddr2 the proper ratios would be 667 is 1:1 and 533 is 4:3.

yea whoops my math was a bit off then lol thanks for fixing my post

 

[nesositel]

You need to buy this:

http://cgi.ebay.com/8GB-4X-2GB-RAM-...ltDomain_0&hash=item3cb5a9c50d#ht_4729wt_1141

This is for example only. Your Dell t5400 is older workstation with core 2 quad XEON CPU's and server chipset intel 5400, that was and still is using FB-DIMM DDR2. Not just any DDR2.
So, from the link above, you will see the specifications for your memory and also the price, so you could search on newegg, tigerdirect e.t.c.
I know because i am searching the same dell t5400 but knowing it is older, for some cheap price . But those XEONS CPU's are expensive.

 

[timta2]

You need to buy this:

http://cgi.ebay.com/8GB-4X-2GB-RAM-...ltDomain_0&hash=item3cb5a9c50d#ht_4729wt_1141

This is for example only. Your Dell t5400 is older workstation with core 2 quad XEON CPU's and server chipset intel 5400, that was and still is using FB-DIMM DDR2. Not just any DDR2.
So, from the link above, you will see the specifications for your memory and also the price, so you could search on newegg, tigerdirect e.t.c.
I know because i am searching the same dell t5400 but knowing it is older, for some cheap price . But those XEONS CPU's are expensive.

How many memory slots do you think his motherboard has? 16? lol. He has the right memory picked out in his initial post.

 

[nesositel]

Sorry, my bad.
Didn't saw that he was already picked up the right kind.
Just wanted to clarify standard ddr2 and FB-DIMM.

 

[cdawall]

Sorry, my bad.
Didn't saw that he was already picked up the right kind.
Just wanted to clarify standard ddr2 and FB-DIMM.

He says fb-dimm in the original post...