y is the X2 not GDDR4?

[shraz]

And why isn't it 512MB x 2 like CPUs?

 

[Chris_B]

And why isn't it 512MB x 2 like CPUs?

Not using ddr 4 probably to keep the cost down, not sure what you mean by the second point, it does come with 1 gig of ram.

 

[Racasdorph]

I thought I saw a benchmark using a 3870x2 with Gddr4? i could swear it

 

[gljvd]

its def cost .

gdr 3 esp at the speed they are using (800mhz or 900mhz ) is most likely pretty cheap these days . If they get enough peformance form it then they should be happy.

The gddr 4 3870x2 should come out in the future unless the r700 is ready at some point

 

[Zinn]

I don't think GDDR4 makes that big of a difference anyway. Case in point the X1950XTX with its 512MB GDDR4 was not much faster than the X1900XTX ... it just had a slightly more annoying name and higher clock speeds.

 

[RikkAndrsn]

it just had a slightly more annoying name and higher clock speeds.

Price was higher, too. That was why I never upgraded.

 

[WhiteZero]

Why is it not GDDR5?

 

[bill_d]

if ddr5 card would cost 2k or 3k

 

[xp3nd4bl3]

unless the r700 is ready at some point

R700 will be ready at some point.

 

[shraz]

okay so it is 512mb x 2

 

[Silus]

I don't think GDDR4 makes that big of a difference anyway. Case in point the X1950XTX with its 512MB GDDR4 was not much faster than the X1900XTX ... it just had a slightly more annoying name and higher clock speeds.

Correct. GDDR4 does consume less power than GDDR3, which should be its main advantage at this point.

As to the OP question, it's definitely cost. The suggested MSRP of the X2 is $449. It wouldn't cost that if it used GDDR4. It would probably end up costing $549 with GDDR4, which, if the most recent performance numbers of the X2 are true, would not make the card appealing at all.

 

[bill_d]

but if the MSRP of a 3870 w/ddr4 = 219
the x2 w/ddr3 should be cheper than 2 single cards

 

[Silus]

but if the MSRP of a 3870 w/ddr4 = 219
the x2 w/ddr3 should be cheper than 2 single cards

Well first of all, the HD 3870 only has that MSRP, due to the 8800 GT. The HD 3870 costs less, because the 8800 GT is the better card, at the same price point.
Also, you're just adding the cost of 2 single cards. To create cards such as these, there's more to it than just slapping two cards together, to create cards like the X2/GX2, which means higher production costs.
And then there's also the nasty bit about profit margins. If the GX2 is faster than the X2 at the same price, ATI will need to do the same they did with the HD 3870 price i.e. lowering the X2 price to be competitive. If the GX2 is not faster, you can bet on seeing a higher price tag than $449 on the X2.

 

[Michaelius]

One of our polish forum members made tests with 3850 OC compared to 3870 and DDR3 at 900MHz had similar performance to DDR4 at 1100.

So most probably they get cheaper ddr3 as it won't affect performance.

 

[j3ff86]

I don't think DDR4 costs a lot more than DDR3. There is a gigabyte 3870 with DDR3 and it's only $20 cheaper.