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5870 Vs "6870" ..

Permabanned
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I have no idea why you think the physical length of each side not being double doesn't take up twice the space. Its a wafer, its not a long thin piece of silicon and you can increase the width as much as you want. Double the size and you'll more than half the amount of cores you get off a wafer as yield goes down at a non linear rate as core size goes up. If there were 100 potential cores at 225mm2, then at 450mm2 you'd have probably 44-47potential cores, a silicon wafer is circular, meaning squares don't fit in perfectly, the bigger the square the more space lost on the edge the bigger the cores get, in general. But thats before yields go down, if on the 225mm2, 100 potential cores, you only got 80 working cores, or a 80% yield, that yield would be substantially down if you doubled the core size, its all theoretical with the numbers I'm using because they arent' real, but the yield's will go down exponentially and at one point just become almost completely unworkable.

At 500mm2 (a bit more, 523 iirc) the GF100 is for all intents and purposes, unmanufacturable, it can't be made at a profit because yields are so painfully low. If AMD have gone from a 330-340mm2 core to a 400mm2, and Nvidia dropped down to a little under 400mm2, you can bet that above 400mm2 is where the yields start to drop very dramatically.

15mm sides up to a 21mm side, doesn't mean a 1/4 drop in cores per wafer, it will mean a noticeably over 50% drop in cores per wafer.

Draw a square, divide it into 15mm sided smaller squares, then divide it into 21mm sided squares, see how big the difference is ;)

The same will happen the other way, drop the size of a 5870 by half, a 5770, and you'll get more than double the cores per wafer, because then out of 200 potential cores, the yield will be higher again, call it 90%, so you'd get 180 cores, vs 80 5870 cores, more than double.
My point was, a square die at 15mm x 15mm goes up to 21mm x 21mm when you double the area. When you double the area of a GPU you can double the transistor count. If that 15mm x 15mm chip has 1 billion transistors, then the 21mm x 21mm will have 2 billion transistors.

The way you've put it suggests you think doubling a GPU's size means you multiply the sides by two, which would result in a core 30mm x 30mm, which would actually be 4x the size not 2x the size, and 4 billion transistors not 2.
gpu.png
 
Man of Honour
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Got any links to statements? Not questioning you, just wondering if they don't mean generally in the next year/two, or maybe drivers, mostly guys who do twitter type stuff for AMD are driver guys.

Sorry not really a twitter person so no idea how to find it again. Just saw it on my facebook "from twitter" feed for one of the developer channels/pages I'm subscribed to. Granted they are mostly driver guys on there so who knows but it was semi officially an AMD statement.
 
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Associate
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So will getting two 5870's be good enough to run most games in the near future at high? (Not counting the spec hungry games like metro 2033 :p ) or will it be worthless compared to just one 6870.

My single HIS 5870 has no problems playing Metro on full graphics.

I only bought this card recently. I am hoping that the 6870 will not blow away the 5870 for this reason but a consequent drop in price of the 5870 would encourage a purchase of a second 5870. That will certainly suffice for the time being.
 
Caporegime
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My point was, a square die at 15mm x 15mm goes up to 21mm x 21mm when you double the area. When you double the area of a GPU you can double the transistor count. If that 15mm x 15mm chip has 1 billion transistors, then the 21mm x 21mm will have 2 billion transistors.

The way you've put it suggests you think doubling a GPU's size means you multiply the sides by two, which would result in a core 30mm x 30mm, which would actually be 4x the size not 2x the size, and 4 billion transistors not 2.
gpu.png

Firstly I never mentioned the size of the sides, in any way what so ever.

You will find that if you make a square 300mm in diameter, fill it up with 15mm squares and fill it up with 21mm squares you will in no way find a 1/4 drop in the number of squares that fit in, if you're very lucky it will be a little over half, if you're unlucky it will be a bit under half.

Seriously you completely confused here, doubling the area does NOT allow you to maintain 3/4's of the amount of cores.

Heres a pretty simple one for you, think of a square, ANY square, now, draw a line through the middle, how many rectangles do you have that are half the size of the square, is it 1.5(which you seem to think it is) or is it, unsurprisingly, 2. Now add those rectangles together and you have, you guessed it, the original square, it doesn't somehow somewhere in there change to let you have 3 fit in.

I really don't understand how you think doubling the gpu area somehow lets you make 3/4's of the number of cores within the same wafer size.

Ok, take a 4cm by 4cm square, fill it with 1cm cpus, you'll get 16, now fill it with 2cm cpus(what you seem to think I said in doubling the sides lengths), how many fit in, 4 squares. You double the sides you do increase the area by 4 times. However, if there was two flaws in the 2 separate 1cm area's, then of the 16 potential cores only 14 would work.

Now if you have those 2 flaws take out 2 of the big cpu's, you're only left with 2 working ones. The bigger the core, the worse the yields. So rather than go from 16 to 4 cores, you've actually gone from 14 working cores, to 2, a MUCH worse drop in cores than increasing the size by 4 suggests.

Now if you only doubled the size and got 8 2cm2 cpu cores in there, and 2 were faulty, you'd end up with 6 working cpu's.

So 14 cores down to 6 working cores, its not half, its less than half, thats how yields go down with an increase in core size.

So in reality if you were getting 100 working cores before, and then double the size, you'd end up with in perfect circumstances 50 cores absolute maximum, but in reality you'd end up with probably 30-40 depending on process quality and luck, etc, etc.
 
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