It should be noted that it's not THAT big of an increase. The latency of RAM is measured in clock ticks. So a CAS latency of 5 for 1066MHz RAM is an actual latency of 4.69 ns.

A CAS latency of 7 for 1600MHz RAM is an actual latency of 4.375 ns. There's very little in it.

Memory speeds increase, but latency doesn't improve very much at all. Since it's basically standing still, it looks like it's moving backwards compared to everything else, but it really isn't.

Keep in mind that P5K does not support DDR3, exception being P5KC, entire P5K3 series, Blitz Extreme and P5K64-WS. As for Asus boards, I don't complain about their products being broken or needed repair, just read the Asus forums and see how many problems people are having with those boards, especially check the forum concerning the specific motherboard you are planning to purchase :tu:

My latest quote....third quote; third supplier
 

Intel Q9550 CPU, 12MB Cache 1333 FSB
Gigabyte GA-EP45DS4P Motherboard (Has copper(brass?) heat pipes)
4GB DDR2-1066 Dual Channel "Reaper" RAM (5-5-5-12)
PC Power 610W Power Supply
Antec 300 case (aluminum case with lots of fans and the whole front is mesh)

Finally I got to talk to someone who understood hardware, my needs and my questions: she knew what RAM latency was, that I needed good case/cooling, knew that DDR2 was still faster (except at the highest end) than DDR3, etc.

BUT ... the one twist she threw at me was: "Do you realize that Microsoft XP can only address 3.2 Gb of RAM so the extra Gig won't be available to you?"

Maybe I should get 3Gb?

Get a 64-bit operating system; Vista or 64-bit XP. There's absolutely no point, particularly if you're doing maths and so 64-bit multiplications come in handy, in running a 32-bit OS on contemporary hardware.

[QUOTE=petrw1;143654]one twist she threw at me was: "Do you realize that Microsoft XP can only address 3.2 Gb of RAM so the extra Gig won't be available to you?"[/QUOTE]Your third supplier is competent, get your computer from them. They have quoted top-quality components (with the possible exception of the OCZ RAM, some might argue that Corsair/Mushkin/Patriot/etc is better, but the RAM as quoted should be fine).

Her statement is mostly accurate -- it's the 32-bit versions of Windows that have problems accessing much more than 3GB of RAM (actual available will vary anywhere between about 2.7GB and 3.7GB, depending on the exact hardware installed, but you'll commonly get around 3.2GB usable. This applies equally for Windows XP 32-bit and Vista 32-bit. As [i]fivemack[/i] said, get a 64-bit operating system. XP64 is generally very hard to find these days (and if you do find it there are often fewer XP64 drivers than Vista64 drivers available), so you should probably go with a 64-bit version of Vista.

Just wondering... won't /PAE be enough to solve the issue of 4GB not being recognised on XP 32bits? As I understand it, this will allow all 4GB to be used. The limitation being that not all the 4GB can be used by a single programme - but you can have 2 programmes using 2GB each.

[QUOTE=James Heinrich;143708]Your third supplier is competent, get your computer from them.[/QUOTE]

That is where I am leaning now .... thanks

[QUOTE=db597;143733]Just wondering... won't /PAE be enough to solve the issue of 4GB not being recognised on XP 32bits? As I understand it, this will allow all 4GB to be used. The limitation being that not all the 4GB can be used by a single programme - but you can have 2 programmes using 2GB each.[/QUOTE]

Never heard of this so I looked it up and found this statement at [QUOTE][url]http://en.wikipedia.org/wiki/Physical_Address_Extension#Windows[/url] [/QUOTE][QUOTE]Windows XP SP2 and later, by default, on processors with the no-execute (NX) or execute-disable (XD) feature, runs in PAE mode in order to allow NX. The NX (or XD) bit resides in bit 63 of the page table entry and, without PAE, page table entries only have 32 bits; therefore PAE mode is required if the NX feature is to be exploited. However, desktop versions of Windows (Windows XP, Windows Vista) limit physical address space to 4 GB for driver compatibility reasons.[/QUOTE]

I have the desktop version of XP with SP3 but how do I know if I am NX or XD? It sounds like I am cooked by the last sentence.

I have Windows XP Pro SP3 with 2x2GB configuration and PAE enabled - system reports 3.25GB (3406060 kB) RAM available.

No matter how you slice it, 32-bit versions of XP and Vista are capped at 4GB total, and from that maximum you have to [url=http://blogs.msdn.com/hiltonl/archive/2007/04/13/the-3gb-not-4gb-ram-problem.aspx]carve out reserved memory for hardware[/url]:[quote]Due to an architectural decision made long ago, if you have 4GB of physical RAM installed, Windows is only able to report a portion of the physical 4GB of RAM (ranges from ~2.75GB to 3.5GB depending on the devices installed, motherboard's chipset & BIOS).

This behavior is due to "memory mapped IO reservations". Those reservations overlay the physical address space and mask out those physical addresses so that they cannot be used for working memory. This is independent of the OS running on the machine.

Significant chunks of address space below 4GB (the highest address accessible via 32-bit) get reserved for use by system hardware:

• BIOS – including ACPI and legacy video support

• PCI bus including bridges etc.

• PCI Express support will reserve at least 256MB, up to 768MB depending on graphics card installed memory

What this means is a typical system may see between ~256MB and 1GB of address space below 4GB reserved for hardware use that the OS cannot access. Intel chipset specs are pretty good at explaining what address ranges gets reserved by default and in some cases call out that 1.5GB is always reserved and thus inaccessible to Windows. [/quote]So if you're luckly, you might get away with as much as 4GB - ~300MB = ~3.7GB; if you're unlucky you might end up with 4GB - ~1500MB = ~2.5GB.

so....where does that leave me in GIMPS
 

... so I accept that I won't have access to 4GB until the day I upgrade to a 64 bit OS that handles it ... and so if I understand GIMPS correctly:

a) This does not in anyway restrict or slow down LL or DC tests
b) P1 Factoring is not resticted or affected
c) I will not be able to do ECM with b1/b2 over about 3.2 GB

Am I close?
Did I miss anything significant re: GIMPS or any of the sub-projects?

I plan to, and want to without restrictions, run Prime95 (and possibly some other related software) 24X7 on all 4 cores.