[nycdunz]

i just noticed i got the corsair valueselect 1gb ram from newegg, i got 4gb, popped em in my new dual 2.7ghz G5, all works wonderful, even passed the hardware test. but notice they are cas 3, does this matter? or are they suppose to be cas 2.5? What's the difference? Because I think the default apple ram that came in my machine is cas 2.5...

can someone please tell me if this would have any noticeable kind of affects on my system? and will it be safe to mix cas3, cas2.5 ram together?

I really hope this doesnt slow down or affect my performance in any way...

[polendo]

Im not sure if you can mix them, but I didn't felt any noticeable speed difference between the 2 types on my mac mini.

2.5 is faster than 3.0 CAS timings, nevertheless It felt the same to me.

[MORT A POTTY]

it is safe to mix them...but your RAM all will default to the slowest CAS latency if you mix them.

[Al G]

The Powermac G5 requires CAS 3 and runs no faster than CAS 3. There's no harm in adding CAS 2.5 (or faster) but there's no benefit either.

[merp]

the G5 memory controller only supports CAS3 timings. the 2.5 RAM usually has the necessary info for DDR controllers to run it at CAS3, but I know that some off-brand RAM that doesn't have the necessary parameters in the EEPROM, and won't work in the G5. Ultimately, it's a wash as to whether or not the CAS2.5 stuff is faster; it only matters if you're going to run it at a faster clock than spec, and since there's no way to O/C a G5 yet, it's irrelevant.

Save your money, stick to CAS3 memory...

Edit: Arg, beat me to it!

[nycdunz]

thanks guys, so g5's recommends CAS 3? phew, that makes me feel much better...

[Scotttheking]

Originally Posted by nycdunz

thanks guys, so g5's recommends CAS 3? phew, that makes me feel much better...

No, it doesn't run any faster than that. So even if you put in CAS 2.5 ram, it'll run at 3.

[cgc]

The old Apple System Profiler used to identify what memory was rated as and actually said next to my one 2-2-2 SIMM that (this is faster, or something to that effect).

[Tyler McAdams]

In theory (when the timings are suported) cas can make a difference... a small difference. When it comes to the latency of your ram, you should know that the more ram you have (read actual ram modules) the more latency you will have. So if you were maxed out in ram on your system it might pay off to use cas 2 qualified ram to reduce some latency.

[badtz]

is there documentation online that indicates that the memory controller only supports CAS 3? curious

[mduell]

Originally Posted by badtz

is there documentation online that indicates that the memory controller only supports CAS 3? curious

I don't have any sources for that specificly, but memory latency in G5 systems is terrible.
And even if it could run at CAS 2.5, it doesn't really matter.

[Todd Madson]

I'm running four sticks of ValueSelect on my G5 2.5 and no problems.

But remember, the system runs at the speed of the slowest link in the
chain so if you have two sticks of CAS3 in there the remainder will run
at that setting.

Although, there was an article at barefeats where the guy there was testing
two identical G5 2.5 dual systems except one was running 8-10% faster than
the other. The faster system was running CAS2 ram exclusively.

Your mileage may vary and I think you would see bigger performance gains
by overclocking the video card or running a 10,000 rpm drive mechanism.

[waxcrash]

Originally Posted by Tyler McAdams

In theory (when the timings are suported) cas can make a difference... a small difference. When it comes to the latency of your ram, you should know that the more ram you have (read actual ram modules) the more latency you will have. So if you were maxed out in ram on your system it might pay off to use cas 2 qualified ram to reduce some latency.

The difference is so small it is not worth the higher price for the lower latency ram.

http://techreport.com/etc/2005q4/mem...y/index.x?pg=1