What is VCM? Or SPD?

[ss69nova]

Ok i just got two mobos that i am playing to build for crunchers. I would like to get the best ram for the mobo.

The mobos are Asus A7SVM. So that means either pc100 or pc133. In the manuel it says that it can handel VCM virtual channel memory, and Enhanced Memory System's high speed drams.

It says it supports Serial Presence Detect. Which it recomends for best performance vs stability.

I went to price watch and i can find SPD ram but what is VCM? Is it a type of ram? Or is it just a protacol?

What type of settings should i look for in a stick of ram?

Any info would be great.

[ronin1967]

VCM is Virtual Channel Memory is SDRAM made I think only by Kingston(maybe more now). It allows "blocks" of memory to interface separately with the controller, and each "block" has it's own buffer. Mutiple tasks can then be assigned their own virtual channels.

[ss69nova]

ok so which is better? VCM or SPD or is it possable to have both?

[ronin1967]

SPD is for Serial Presence Detect. It's not a special type of memory it's standard memory that has an additional chip which has information specific to the memory which it sends to BIOS so that it can be used at optimal settings. There isn't a performance gain with SPD just detection, VCM is suppose to improve performance.

[larva]

VC memory does improve performance, but only to a small degree. The only chipsets to support this memory type where VIA units, and this was before competent memory controller design came to VIA products. BX with normal SDRAM seriously outperforms VIA 694x, even when it is equiped with VCM.

[ss69nova]

larva
VC memory does improve performance, but only to a small degree.

So is it worth the extra money to get vc p133 ram? We are talking 140 170 $ for a 512. spd starts at 54.00.

SPD has nothing to do with speed it just alows the bios to detect it. Is this really a benfit?
What would i gain from spd?
Will the bios still beable to read the settings?
SPD just makes this process faster?

[larva]

I can't answer that question with all certainty, VCM was and is a rare thing. I am inclined to say no though, at the prices you mentioned. But if SETI is the object, perhaps it might have enough impact to make it seem a good value. I just don't have the experience with KT133a, VCM, and Athlons in general to quantify the improvement for your application. For anything besides SETI, I think it is safe to say no, it wouldn't be worth that differential.

As far as SPD goes, it is in no way vital. To this day virtually every time I try to use it it doesn't work. For instance on my current board selecting SPD produces the fastest possible timings, and I find this behavior typical. Back when SPD first appeared, I suspected that the SPD eeprom's where typically mis-programmed. These days I am inclined to think that SPD is flawed on a more basic level. All SDRAM made in recent years has it though, I find it unlikely you could find any ram without it to buy. Just set your memory timing manually, as I don't trust SPD nearly as far as I can throw it.

[ss69nova]

thanks alot for the input.