Why the 1 GB per slot limit on A64 mobos?

[KF]

Since the CPU has the memory controller, why do Athlon 64 mobos have a limit of 1 GB per slot? Every mobo I ever had had a memory limit way beyond what was available at the time the mobo was made. I'd like to be able to go over 4 G in 3 or 4 years when I still have the mobo.

 

[Peter]

That's because there are no RAM chips larger than 512 Mbit currently. On an unbuffered DIMM, you can have no more than 16 of those, so there's your one-GByte DIMM. Registered DIMMs, as seen on socket-940, may have twice as many chips on, so you can have 2-GByte DIMMs from currently available chips there.

 

[KF]

Thanks Peter. But I meant the 1G limit stated in motherboard reviews. It sounds like they are saying you will never be able to address over 1 G, no matter that the chip size is going to get much larger over the years. I've got old mobos that started out with (very expensive) 32 M and now are maxed at (cheap) 512M. That's a factor of 16 larger. I'd like to have that kind of opportunity with mobos I buy today. I'd like to start with 1G on an A64 mobo.

Are there perhaps not enough address lines on the standard DDR DIMM slot? Then again, maybe they'll phase out DDR in a couple of years, and I won't be able to expand anyway.

 

[Peter]

Who knows whether 1-Gbit DDR chips are ever going to happen, before the market moves to DDR-2? The majority of chip production is still on 256-Mbit, the 512-Mbit chips being the rare and expensive ones.

Besides, there already are 1-GByte unbuffered DIMMs, so even a socket-754 board lets you put 3 GBytes in.

In 3 to 4 years, you probably won't find any DDR-1 DIMMs in the shops, at least not for realistic prices. PCs aren't that future proof - just look back. What do you tell someone who wants more RAM onto their three year old mainboard?

 

[DAPUNISHER]

Originally posted by: Peter


In 3 to 4 years, you probably won't find any DDR-1 DIMMs in the shops, at least not for realistic prices. PCs aren't that future proof - just look back. What do you tell someone who wants more RAM onto their three year old mainboard?

That's sound reasoning. Unless the industry changes radically history shows standards are soon left behind for new ones so futureproofing is a oxymoron when speaking of PC's.