I don't know about X38, but as you can see from my signature info I have two P35 chipset motherboards
(P5K-E, P5K-Deluxe) both running 8GB DDR2.
I've had ZERO problems with these systems, they "just work" at stock timings for CPU / memory, and I've been
able to overclock both the CPU and memory to expected levels without feeling that I've run into ANY difficulties
due to the quantity or type of RAM.
One PC uses G.SKILL DDR2-800 unknown chips, the other SuperTalent DDR2-533 with micron chips, so I don't feel that
I've been especially "lucky" in getting these configurations stable and wouldn't have had the same results if I'd used any
other 2GB DIMM memory brand of reputable quality.
> 1. Do the top MB choices reliably support 8GB?
YES! At least the ones I've researched. I'd say the P35 or X38 chipsets would be the way to go IN GENERAL for
a new quad core system. Regardless of RAM issues, it seems to me the NVIDIA chipsets have too many "quirks" and are
rather bloated in price and lacking in compatibility etc. anyway.
> 2. Do the 8GB ram stick choices generally scale back to 4 by pulling 2 sticks?
Absolutely unquestionably. Just make some effort to pull the *CORRECT* 2 sticks so that you're
still running in "dual channel" mode with the 2 sticks left in the PC, this gives a SLIGHT
(maybe inconsequential, really) performance benefit since the DIMMS will interleave better to
have lower latency and higher throughput. It's LESS relevant to do this with 2GB capacity DIMMs
of today's dual rank 128x8 (16 chips) configuration because even a SINGLE DIMM is going to
be somewhat bank interleaved all by itself given that it has two ranks of memory on it that
interleaves anyway.
But with 2 installed DIMMS in a dual channel spread you get additional interleaving over
the 2 DIMMs as well. On INTEL architectures the WRITE bandwidth is quite low ANYWAY
so it's probably irrelevant for that but your READ bandwidth would speed up a bit.
The motherboard manuals make it rather insanely confusing to find out the RIGHT 2 slots
for a bank giving often contradictory info. on color coding vs "Channel A" "Channel B" labels.
Anway that's the ONLY reason it'd matter even a little and it's pretty irrelevant in most cases anyway.
Actually you can pull 3 DIMMs and end up with ONE DIMM in single channel operation if need be
on the motherboards I know of, and THAT may be important (to run with 2GB temporarily)
because VISTA 64 and I think one other MS 64 bit OS has a horrible BUG where it
will CRASH 100% of the time during INSTALL if you have more than 3GB installed, the only
solution is to install with 3GB or less present in the box.
As soon as you DO install, though, it will be able to download a patch (lovely, eh?) to
'fix' the issue and let you install numerous other gigabytes of RAM and have no troubles thereafter.
> 3. Does 8GB restrict ram choices, or timing setting choices, over having 4GB? To what degree?
The timing reduction is insignificant. The command rate will go from like 1T to 2T which is like
less than 2% worse according to benchmarks that I recall. However unless you had only
2 DIMMs of single rank (8 chip) design [probably meaning they're 1GB capacity or less each DIMM],
you'd probably default to and/or need to run at 2T anyway. So you gain 6GB capacity by running
4 DIMMs of 2GB each vs 2 DIMMs of 1GB each, and the massive gain in PERFORMANCE due to
the extra cache / application memory FAR FAR outweighs the SLIGHT timing hit you take on
command rate or peak overclockability of the memory set.
Keep in mind the quad CPUs have a LOT of L2 cache, and they need it, but the reason they
need/have it is so that they WON'T all be trying to access main RAM a lot of the time repetitively.
So your actual memory BANDWIDTH requirements are much LESS on such a CPU with 8GB or 12GB
L2 cache vs. many lesser common CPUs which may only have 1MB or 512KB cache.
As long as you run a 64 bit OS, MORE memory is virtually always better for performance (for
disk cacheing at the very least even if for no other reason) than less but faster memory.
Certainly running VMs and other memory heavy applications give you lots more reasons why
more memory is better than half the memory running at 5% higher speed or whatever.
> 4. (For early testing of the machine) - can a machine with 8GB installed still start Windows XP Pro reliably (albeit with only 3.5GB or so) showing?
See above wrt. OS limits of 3GB due to installer bugs. Other than that you should be able to
run XP 32 or XP PRO 32 with 8GB installed but it only accessing 3.5 or so due to 32 bitness.
There's a "/PAE" switch that can actually let XP use more memory in certain ways, google for the MS
KB articles about that etc. It may come in handy if you need to run that way.
With XP 64 / XP PRO 64 / VISTA 64 or UNIX 64, though, you'll have no troubles once they're
installed and patched to the latest service packs & updates.
> 5. Are there any hardware incompatibilities inherent to putting in this much ram?
Not really. The "memory compatibility" / "qualified memory vendor" lists on some (all?) MB
vendor sites seem to be a bad joke. There are a FEW DIMM manufacturers / products
that seem to fail to be working properly in certain motherboards according to those lists,
but the vast MAJORITY of products haven't even been tested to confirm they either work
or don't work, so the lists are pretty useless at picking DIMMs.
In my experience you shop for quality DIMMs from reputable vendors / resellers at the best
price and look aroung a little for anecdotal evidence that they're working well for people
and buy them and try them. I haven't had a problem in many many years doing that,
and that only when there had been a new generation of 512KB DIMMs that had more
address lines than the motherboard chipset could support.
Clearly there's only one generation of 2GB capacity DIMMs, 16 chip, dual rank, 128x8,
so as long as you buy DDR2-unbuffered-NON-ECC 240 pin DIMMs you should be fine
in architectural compatibility.
Some motherboards have BIOS that doesn't let the user control much ANYTHING manually
in terms of DIMM timing or clocks etc. Some motherboards DON'T have capacity to even run
any DIMM at a voltage higher than 1.8V. Some BIOSes don't know what EPP data is or don't
deal with SPD data timings properly.
In such cases of junky low end non "enthusiast" BIOS motherboards it's unsurprising people
won't be able to get enthusiast / EPP DIMMs or DIMMs that the manufacturer REQUIRES
higher DIMM voltages on (even to run at SPECIFIED speeds) to work properly.
But any reasonable (P35, persumably X38, etc.) motherboard with even a semi-reasonable
BIOS will "just work" and furthermore will give you all the control you could ever want of
cycle timings, DIMM voltages, etc. if you really do feel the need to adjust those while you
overclock or if you buy some super fancy super high speed memory that needs 2.3V to work
or whatever...
Enjoy / good luck / don't worry.
I just bought some of each of these, seemed like good deals:
$99/4GB after rebate
http://shop1.outpost.com/produ...sr:SEARCH:MAIN_RSLT_PG
$103/4GB no rebate:
http://www.ewiz.com/detail.php?name=T8UB2GC5&show=p
They'll go into another P35 or X38 + Yorkfield quad. system I'll build in a few months.
Originally posted by: supergrade
Looking to build a highend machine - "in 6 months time the hardware will be SO much better!" has dragged out for way too long now.
I am entertaining the idea of Quad CPU 8GB. It would be of use to me to have VMs/IDEs/dev server testing on one device. Would 4GB work? Probably; but I'd at least like to have the option to run up to, and possibly start with, 8.
It's been a while since I've done a build - I come in now and notice forums where people (mostly 680i users; but even others) face concerns over MB/Ram combos running reliable. I need 100% reliability.
1. Do the top MB choices reliably support 8GB?
2. Do the 8GB ram stick choices generally scale back to 4 by pulling 2 sticks?
3. Does 8GB restrict ram choices, or timing setting choices, over having 4GB? To what degree?
4. (For early testing of the machine) - can a machine with 8GB installed still start Windows XP Pro reliably (albeit with only 3.5GB or so) showing?
5. Are there any hardware incompatibilities inherent to putting in this much ram?
Any anecdotes or suggestions of good X38/Ram hardware combos for 8GB appreciated.
PS: Posting on "Motherboard" forum as I see this as more of a mobo compatibility issue.
Facebook
Twitter