Quote from: DeathAndTaxes on October 30, 2013, 01:32:54 AM

Quote from: aerobatic on October 29, 2013, 11:35:40 PM

unrolled cores are not necessarily crappy cores.

Agree however they can't be compared directly. It takes 80 clock cycles for a Bitfury rolled core to complete a hash where as an unrolled core will complete a hash in one clock cycle. So clock for clock Bitfury 756 rolled cores complete about the same number of hashes are 9 unrolled cores. This isn't to say one method is better than another. They are just different. Given similar die efficiency a 9 unrolled core chip and a 756 rolled core chip would be comparable size, power usage, and hashpower.

Another way to look at it is GN's 768 nonces per clock cycle would be the equivalent of Bitfury announcing they have a new processor with 61,440 rolled cores.

Any way you slice it a single GN processor is a staggering number of cores each one processing a full nonce every clock cycle. No existing design comes close to putting as much hashpower in a small package (Cointerra probably will be similar but so far specs are unknown).

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And much of that can be expressed as a GH's / Die area, that would give you a measure of efficiency - or in its simplest terms, GH's/S. per square mm of die area - at least when comparing like for like (all 28nm's for instance)

Agreed and by that metric the GN is extremely dense. A huge amount of hashing power per mm2.

I remember reading that the Hashfast was about 6.5x6.5mm, or 42mm² The bitfury chips are only 3.8x3.8, or 14mm², about 3 times the surface area.

According to this it only takes 65 cycles for a bitfury core to compute a hash, not 80.

Quote from: bitfury on June 08, 2013, 04:30:46 AM

1. 756 double sha256 cores. 61+4 kernel (61 clock cycle computation 4 clock cycle load).

2. There's asynchronous 'match' signal - the only thing that core sends out. And some busses to load data.

3. wirebond. die is laid normally in cavity. i.e. it is not flip-chip and not arranged to give heat into anything else, but PCB.
It is actually not complex to dissipate 3W... Maybe even 5W with metal-core PCB and proper cooling. That's what we'll see.

Also, the theoretical speed of the bitfury chips (which is what we're comparing) was about 5Gh/s. 40nm²/28nm² = 2.25, so HF should be able to cram 2.25 times twice as many transistors in the same amount of space. And those transistors should be faster, with about 0.75 times the transistor gate capacitance.

So, if you were able to scale the bitfury design to 28nm, and increase the surface area to 42mm², you would expect the theoretical speed to equal 2.25*1.5*3* = 50.6Gh/s. On the other hand, it would only take about 33W as well.

It's interesting that the W/Gh/s would actually be a little better, for bitfury while the surface area efficiency seems to be about 10x for HashFast.

It could be that the BF chips may have been deliberately spread out in order to make it easier to keep the chips cool, obviously the HF chips require a lot more cooling. It's actually likely that complete miners are actually cheaper to build and deploy using bitfury chips due to the reduced cooling requirements.