A64 questions - I'm still in the AXP-M arena

[fscussel]

Hello agian to everyone, im now-a-days using the signature system but I plan moving to A64 in the beggining of 2006. What I want to know if how the DDR memory works in the A64 arena, if it's the same as in the AXP-M, where you try to have the lowest timmings (2-2-2-11) with the higher FSB (that tops out at around 250mhz in the NF7-S 2.0), always using 1T (or CPC ON), and 1:1 with the CPU. Is this all the same in A64 or is it hard to achive any of those things? Also, I have heard that memory speed increase doesnt make difference at all, like if you have 250mhz 1:1 with the CPU it will not make too much difference if you go to 300 1:1 with the CPU... is that true? Everyone fell free to type a lot cause I'm completely new to the A64 world. Thanks.

 

[imported_Kensai]

In 2006 there will be socket M2.. Wait until then to ask us..

 

[fscussel]

Well Im not that type that buy technology the day after it hit the market, so I will probably buy an 939 A64, and Im changing my memories this month, so I would like to know about how A64 works to use the same memory when I move to it.

 

[Furen]

The same except that you dont need to keep a 1:1 htt/ram ratio, so if your ram is holding you back you can just increase the divider without penalty.

 

[coomar]

look at the top of this forum, there is a sticky there for a reason

 

[Ronnie]

If your running crucial ballistix, then that will be fine in your 939 board when you make the switch.

 

[fscussel]

Originally posted by: Ronnie
If your running crucial ballistix, then that will be fine in your 939 board when you make the switch.

Well, the problem is that ballistix can't do CAS2 after 210 mhz!

 

[Bona Fide]

Originally posted by: fscussel

Originally posted by: Ronnie
If your running crucial ballistix, then that will be fine in your 939 board when you make the switch.

Well, the problem is that ballistix can't do CAS2 after 210 mhz!

You've got crappy Ballistix then...are they DDR400 sticks? Most of them go right up to DDR500 with 2-2-2 or 2-3-2 timings.

 

[fscussel]

Originally posted by: Bona Fide

Originally posted by: fscussel

Originally posted by: Ronnie
If your running crucial ballistix, then that will be fine in your 939 board when you make the switch.

Well, the problem is that ballistix can't do CAS2 after 210 mhz!

You've got crappy Ballistix then...are they DDR400 sticks? Most of them go right up to DDR500 with 2-2-2 or 2-3-2 timings.

Well, maybe it's because i'm in the AXP-M nforce2, because both sticks do the same, 210 2-2-2-11 and 230 at 2,5-2-2-11... that with 2.9 volts, raising it more doesnt help anything... Im actually not sattisfaied with those ballistix.

 

[dannybin1742]

i'm actually waiting for the dual cores to come down in price, i used to run an axp 2200+ mobile, IMO if you need somthing to tide you over for a bit, i would highly suggest a s754 A64 board with processor, that what i did, i got in cheap, and i have an a64 3200+ 1mb cache (2ghz) i didn't oc this at all and i'm very very happy with its performance, my 2200+ was oced to 2.4ghz, and it is slower than what i have now,

if you are looking for a s754 combo, look in fs/ft threads, there are lots and they should be very cheap, i got my stuff off the fs/ft boards, and i used my ddr from my axp system so it made the upgrade cheap

 

[Hacp]

That should be right... 2.9 volts for 210 2-2-2-X is awesome. Ballistix usually requires around 3.2 volts to get around 240-250 FSB

 

[Munky]

The A64 benefits mostly from the on-die memory controller, so the memory latency is about 40ns or even less, whereas the AXP has a latency of 80ns if you're lucky. Also, the A64 has the ability to use all the bandwidth available from dual channel ram, whereas the AXP got almost no benefit from dual channel because of the FSB limitation.

The result of this is that even with cheap memory running at 2.5 cas 2T timings you will still get much better memory performance with an A64 than with fast, expensive ram on a AXP. And, because the cpu controls the memory directly, the penalty from running a lower memory divider is pretty small, and only the result of the slower memory, not because of async timings. In fact, the memory always runs off a divider from the cpu frequency, so there's really no such thing as a 1:1 ratio on the A64.

So, even with cheap ram, you will still get a big improvement from switching to A64. And the fact that you can still use your old ram is another good reason to switch over.

 

[Fern]

Originally posted by: fscussel
What I want to know if how the DDR memory works in the A64 arena, if it's the same as in the AXP-M, where you try to have the lowest timmings (2-2-2-11) with the higher FSB (that tops out at around 250mhz in the NF7-S 2.0), always using 1T (or CPC ON), and 1:1 with the CPU.

Short answer is "NO", so to add just a bit to what to Munky is saying...

There is no "FSB" on an a64 system

I'm in the same boast as you, I've only got to build to some a64 systems for others. But don't have one myself to play with.

In trying to understand the a64 thingy I've found it helpful to realize/accept that there is NO Front Side Bus. Gotta drop that way of thinking

Fern

 

[Concillian]

The A64 works in that there is a memory bus speed directly tied to the CPU speed. That is, the memory always operates and CPU speed divided by an integer number. Because of this 1:1 isn't necessary to get the highest performance. equal CPU/RAM speeds can be achieved with different dividers and performance will be equal.

For example 240 MHz HTT x 10 with 166 divider for RAM speed will give 2400 MHz CPU and 200 Mhz RAM. this will perform the SAME as 12x200 with RAM 1:1 (2400 MHz CPU / 200 MHz RAM). This is the additional flexibility of the A64.

THe AXP and the A64 both do not need extreme amounts of memory bandwidth to offer very good performance. In neither case do you see incredibly signfiicant performance gains from higher memory speeds. This was outlined by AT in this article: http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=2469

Going from 200 --> 250 MHz nets you relatively small performance gains. So it's generally not worth spending extra money to get extreme memory performance. 200-230 MHz at 2-2-2 or 2-3-2 is perfectly adequate, and is not very expensive these days. The bottom line is that you don't need to worry too much about the memory speed or the memory divider. The on die memory controller seperates things out nicely such that some issues that used to exist have disappeared.

In general, any memory that works well on an nF2 will also work well on nF4 or nF3.

 

[fscussel]

ok, thanks for all this info, just another question, is there any requirement to operate in 1T, or any dual channel kits will work in 1T? also, what is fastest, 300mhz at 2.5-3-3-X or 250 at 2-2-2-X in the A64 plataform?

 

[fscussel]

Originally posted by: Hacp
That should be right... 2.9 volts for 210 2-2-2-X is awesome. Ballistix usually requires around 3.2 volts to get around 240-250 FSB

Humm as far as I know ballistix doesn't react to voltage increase over 2.95 volts, so it's dangerous using it at 3.2 volts even if it's well cooled, do you use that every day?

 

[Concillian]

generally low latency is better for A64 than high bandwidth.

230-250 at 2-2-2 is probably better, but the differences will be VERY minimal.

While most nForce2 BIOS required a re-flash to go from 1T to 2T (CPC on / CPC off as some BIOS referred to it) Most nForce3/4 BIOS have an option in the BIOS for 1T 2T so there is no requirement. But 1T will be somewhat faster. There should be no problem with most dual channel sets making 1T, but if you use more than 2 DIMMs you will not be able to maintain 1T.

Check some of the memory reviews from AT, like this one:
http://www.anandtech.com/memory/showdoc.aspx?i=2416&p=10

You see that highest performance is achieved at lower speeds but 2-2-2 performance as opposed to something like the corsair which got highest perforamnce at 295 MHz and 2.5-4-3. Spend some time looking at the various memory reviews and you'll see that even 220-230 MHz 2-2-2 performs very well compared to high bandwidth memory. latencey seems to rule over bandwidth.

But I have to emphasize that the differences are pretty small here. Sure it looks big when you chart out some of the most memory sensitive benchmarks available. But in real world performance, you don't really have to worry too much becuase the differences are significantly smaller than what is shown in these very specialized testing scenarios.

Buy what is cheaper, because the differences are small enough that it's hardly worth it to max this part of your rig out. If you're looking at the best memory because your gaming performance matters, for instance, you shouldn't worry about maxing your memory until you have a 7800 GTX, because per dollar spent, performance gains are much better from a better video card than from better RAM.

 

[Ronnie]

Originally posted by: fscussel
ok, thanks for all this info, just another question, is there any requirement to operate in 1T, or any dual channel kits will work in 1T? also, what is fastest, 300mhz at 2.5-3-3-X or 250 at 2-2-2-X in the A64 plataform?

The crucial ballistix I run at 2.5-3-3-10 @ 260fsb 1t of course on my 3200winnie. My 3000+ venice I run on vapo @345Htt with tccd memory 3-4-4-8 with a 9/10 divider. If the board you choose likes the ballistix I would stick with that. There really is not that much difference in running your ballistix in the 250-270 range at 2.5-3-3-10 timings. That being said if you decide on a venice with a low multi and need high htt you can't go wrong with tccd memory.

 

[fscussel]

Well, I will certainly not keep these Ballistix, mostly because I will not move to the A64 in the next 6 monts - 1 year, and memory is very important in the AXP, so I'm really considering the OCZ 4000VX Gold mostly because it's covered all the way up to 3,5V +5%, so I can use everyday at those level os volts... BUT, I have not decided yet because OCZ also have the PC3200 GOLD, wich is using UTT-BH chips, that almost certain can get to 250mhz (2-2-2-X) with 3,6 volts, the problem is that it's warranty only covers 3.1 volts +5%, but it's tempting because it cost 30-40 dolars less for 2x512 than the 4000 VX.