ANTMINER C1 Discussion and Support Thread

[soy]

I tested underclocking-volting the C1.

The best setting was suggested by another user 2 weeks ago:

675/200 530W  803Mhs 0.66W/Mhs
760/250 790W 1008Mhs 0.783W/Mhs

FYI I have an EVGA 1300W gold.

Could you locate that post please?  Your's seems to be the first reference to 0.66W/Mhs on this or the S3+ forums when I search 0.66W/Mhs.

[notlist3d]

I tested underclocking-volting the C1.

The best setting was suggested by another user 2 weeks ago:

675/200 530W  803Mhs 0.66W/Mhs
760/250 790W 1008Mhs 0.783W/Mhs

FYI I have an EVGA 1300W gold.

Could you locate that post please?  Your's seems to be the first reference to 0.66W/Mhs on this or the S3+ forums when I search 0.66W/Mhs.

Looking at the GHs i think it is C1.   No S3+ can do 800 GHs.   And it's to high for S5.  

So i'm sticking with guess of C1

[soy]

I tested underclocking-volting the C1.

The best setting was suggested by another user 2 weeks ago:

675/200 530W  803Mhs 0.66W/Mhs
760/250 790W 1008Mhs 0.783W/Mhs

FYI I have an EVGA 1300W gold.

Could you locate that post please?  Your's seems to be the first reference to 0.66W/Mhs on this or the S3+ forums when I search 0.66W/Mhs.

Looking at the MHs i think it is C1.   No S3+ can do 800 MHs.   And it's to high for S5. 

So i'm sticking with guess of C1

I ws looking at the .66 which would be watts per gigahash not megahash?  The efficiency would seem very good unless you're off by the difference between megahash and gigahash which then would be quite bad.  I looked on the S3+ for the frequency and voltage which might correspond as S3's have the same chips as the C1.

But I couldn't find your reference.

[notlist3d]

I tested underclocking-volting the C1.

The best setting was suggested by another user 2 weeks ago:

675/200 530W  803Mhs 0.66W/Mhs
760/250 790W 1008Mhs 0.783W/Mhs

FYI I have an EVGA 1300W gold.

Could you locate that post please?  Your's seems to be the first reference to 0.66W/Mhs on this or the S3+ forums when I search 0.66W/Mhs.

Looking at the MHs i think it is C1.   No S3+ can do 800 MHs.   And it's to high for S5. 

So i'm sticking with guess of C1

I ws looking at the .66 which would be watts per gigahash not megahash?  The efficiency would seem very good unless you're off by the difference between megahash and gigahash which then would be quite bad.  I looked on the S3+ for the frequency and voltage which might correspond as S3's have the same chips as the C1.

But I couldn't find your reference.

Thanks for warning about MHs.  I did make a mistake on not using GHs.   

And your correct about same chips.  I would guess we will be close to S3 numbers, but cannot say for sure this is one miner I have not underclocked yet.

[soy]

I tested underclocking-volting the C1.

The best setting was suggested by another user 2 weeks ago:

675/200 530W  803Mhs 0.66W/Mhs
760/250 790W 1008Mhs 0.783W/Mhs

FYI I have an EVGA 1300W gold.

Could you locate that post please?  Your's seems to be the first reference to 0.66W/Mhs on this or the S3+ forums when I search 0.66W/Mhs.

Looking at the MHs i think it is C1.   No S3+ can do 800 MHs.   And it's to high for S5.  

So i'm sticking with guess of C1

I ws looking at the .66 which would be watts per gigahash not megahash?  The efficiency would seem very good unless you're off by the difference between megahash and gigahash which then would be quite bad.  I looked on the S3+ for the frequency and voltage which might correspond as S3's have the same chips as the C1.

But I couldn't find your reference.

Thanks for warning about MHs.  I did make a mistake on not using GHs.    

And your correct about same chips.  I would guess we will be close to S3 numbers, but cannot say for sure this is one miner I have not underclocked yet.

The numbers you seem to have faith in claim that at 67% of normal wattage he's getting only a 79% decrease in hashrate.  That's even if his wattage is correct at normal frequency and voltage.

At normal frequency and voltage he claims 790watts.  At normal frequency and voltage after an hour I had 1008GH/s but at 818 watts and after 2 hours I had 1002.88 @ 819watts.  

I see from numbers on the S5 forum that my cheap power supplies run about 8% less efficient.  If I reduce my power usage by 8% I get 753 watts.  So, maybe my supply isn't 8% inefficient.

At 250M/0760 I got 1233GH/s/w or .811w/GH/s.
At 250M/0675 I got 1228GH/s/w or .814w/GH/s
At 243.75M/0675 I got 1242GH/s/w or .8059w/GH/s

So, you can see why I find it incredible that somebody went from .783 down to .66 because we're talking about miner efficiency change not supply efficiency change as supply efficiency shouldn't change that much in that wattage span.

As I said previously, I did see better figures at 200M on an S3 at stock voltage but it was during the coolest part of the day and ambient temperature seems to be a critical factor when measuring efficiency.  

I have not tried 200M/0675 yet but I will eventually.  

Oh, and my pumps and radiator fans are on a supply divorced from the C1 and not included in the calculations.

[tbolt]

I tested underclocking-volting the C1.

The best setting was suggested by another user 2 weeks ago:

675/200 530W  803Mhs 0.66W/Mhs
760/250 790W 1008Mhs 0.783W/Mhs

FYI I have an EVGA 1300W gold.

Could you locate that post please?  Your's seems to be the first reference to 0.66W/Mhs on this or the S3+ forums when I search 0.66W/Mhs.

The top of page 72
Post # 1421

He meant 0.66W/GHs

[soy]

Okay, in the post he says the most efficient test was 575-590watts, 804-817GH/s so the best would be (575w/817GH/s) or .703w/GH/s.  The 1008GH/s test doesn't show a wattage.  His highest frequency test 1123GH/s drew 943watts or .839 w/GH/s.

Wish he had provided the watts at stock settings but yes, these are good numbers, better than mine.

[thedreamer]

Okay, in the post he says the most efficient test was 575-590watts, 804-817GH/s so the best would be (575w/817GH/s) or .703w/GH/s.  The 1008GH/s test doesn't show a wattage.  His highest frequency test 1123GH/s drew 943watts or .839 w/GH/s.

Wish he had provided the watts at stock settings but yes, these are good numbers, better than mine.

I thought I did, but stock was 1008 / 802Watts @ .74v

The best was 805-821GH/s @ 575-600 watts between all 3 C1's I have. After that they start sucking Juice like my 3year old  .

I stopped using them as I'm concentrating on much more efficient miners for now (SP20's / S5's), but in a few days my $0.0779 / KWh kicks in and I'll put them to work in my office as they are quiet as heck, so the quiet factor I agree is much better at the trade off , of low hash rate/ high power usage.

On the other hand, now that I think of it, it's like an Avalon 4.1. I think those go down to 800GH/s @ about 550 watts and are very quiet. Almost the same I guess. I'll have to try one.

[notlist3d]

Okay, in the post he says the most efficient test was 575-590watts, 804-817GH/s so the best would be (575w/817GH/s) or .703w/GH/s.  The 1008GH/s test doesn't show a wattage.  His highest frequency test 1123GH/s drew 943watts or .839 w/GH/s.

Wish he had provided the watts at stock settings but yes, these are good numbers, better than mine.

I thought I did, but stock was 1008 / 802Watts @ .74v

The best was 805-821GH/s @ 575-600 watts between all 3 C1's I have. After that they start sucking Juice like my 3year old  .

I stopped using them as I'm concentrating on much more efficient miners for now (SP20's / S5's), but in a few days my $0.0779 / KWh kicks in and I'll put them to work in my office as they are quiet as heck, so the quiet factor I agree is much better at the trade off , of low hash rate/ high power usage.

On the other hand, now that I think of it, it's like an Avalon 4.1. I think those go down to 800GH/s @ about 550 watts and are very quiet. Almost the same I guess. I'll have to try one.

It's nice to see a under clock on these.  With summer soon I will move to underclocking.  I currently have been working on exhaust getting it set decent.  I might do a total overhaul to make it through summer not sure at this point.

On Avalon 4.1 I have been playing around with it last couple days: https://bitcointalk.org/index.php?topic=1008726.0  

I also went through and cleaned a lot of my miners most were not to bad.  But after using some canned air I suggest if you have not cleaned your radiators out for your C1's, it's amazing how much dust it collected compared to the inside of the miner.

[soy]

Okay, in the post he says the most efficient test was 575-590watts, 804-817GH/s so the best would be (575w/817GH/s) or .703w/GH/s.  The 1008GH/s test doesn't show a wattage.  His highest frequency test 1123GH/s drew 943watts or .839 w/GH/s.

Wish he had provided the watts at stock settings but yes, these are good numbers, better than mine.

I thought I did, but stock was 1008 / 802Watts @ .74v

The best was 805-821GH/s @ 575-600 watts between all 3 C1's I have. After that they start sucking Juice like my 3year old  .

I stopped using them as I'm concentrating on much more efficient miners for now (SP20's / S5's), but in a few days my $0.0779 / KWh kicks in and I'll put them to work in my office as they are quiet as heck, so the quiet factor I agree is much better at the trade off , of low hash rate/ high power usage.

On the other hand, now that I think of it, it's like an Avalon 4.1. I think those go down to 800GH/s @ about 550 watts and are very quiet. Almost the same I guess. I'll have to try one.

Okay.  So, $0.0779 will be your power cost.  Down here where it will get hot this summer my bill shows power to cost $0.075 but when I add in taxes but  not line charges I see $0.0805 but it's not all that clear with their adjustments.  

I worry about the heat damaging the ASICs.

To be honest, using the Kill-A-Watt, I don't see a big deal in cost savings when tuning for lower energy but I haven't tried the big jumps down.

Interestingly, with your numbers for C1 run at almost stock frequency and voltage, your 1008 / 802Watts @ .74v, compares well with these I took: after 1 hour at 250M/0760 I had 1008.57 / 818 watts for .811w/GH/s but the same unit at 2 hours showed 1002.88 / 819 watts for .816w/GH/s.  Ambient was 80°.  So reading of 802 watts is 98% of my 818watts.  That's only a 2% difference in supply efficiency.  

I'm using four 360 watt LED power supplies each modified with a heatsink added to the bridge rectifier, the one turn pot changed out for a Bourns 3299w-501 500 ohm trim pot that has, what, 20 turns from 0-500 ohms for more precise adjustment of the output voltage, and each supply has added a 6 amp 120vac line filter (reducing noise so it doesn't disturb my TV watching/recording), but, each supply costs under $25 with free shipping.  Each supply drives one blade.  I don't put them in parallel anymore as it's easy to burn one up in parallel.  Then again I had to build my PCIE harnesses.  Also I add 3½ digit LED voltage readouts to each as it's easier to tell if there's a problem.

[thedreamer]

Okay, in the post he says the most efficient test was 575-590watts, 804-817GH/s so the best would be (575w/817GH/s) or .703w/GH/s.  The 1008GH/s test doesn't show a wattage.  His highest frequency test 1123GH/s drew 943watts or .839 w/GH/s.

Wish he had provided the watts at stock settings but yes, these are good numbers, better than mine.

I thought I did, but stock was 1008 / 802Watts @ .74v

The best was 805-821GH/s @ 575-600 watts between all 3 C1's I have. After that they start sucking Juice like my 3year old  .

I stopped using them as I'm concentrating on much more efficient miners for now (SP20's / S5's), but in a few days my $0.0779 / KWh kicks in and I'll put them to work in my office as they are quiet as heck, so the quiet factor I agree is much better at the trade off , of low hash rate/ high power usage.

On the other hand, now that I think of it, it's like an Avalon 4.1. I think those go down to 800GH/s @ about 550 watts and are very quiet. Almost the same I guess. I'll have to try one.

Okay.  So, $0.0779 will be your power cost.  Down here where it will get hot this summer my bill shows power to cost $0.075 but when I add in taxes but  not line charges I see $0.0805 but it's not all that clear with their adjustments. 

I worry about the heat damaging the ASICs.

To be honest, using the Kill-A-Watt, I don't see a big deal in cost savings when tuning for lower energy but I haven't tried the big jumps down.

Interestingly, with your numbers for C1 run at almost stock frequency and voltage, your 1008 / 802Watts @ .74v, compares well with these I took: after 1 hour at 250M/0760 I had 1008.57 / 818 watts for .811w/GH/s but the same unit at 2 hours showed 1002.88 / 819 watts for .816w/GH/s.  Ambient was 80°.  So reading of 802 watts is 98% of my 818watts.  That's only a 2% difference in supply efficiency. 

I'm using four 360 watt LED power supplies each modified with a heatsink added to the bridge rectifier, the one turn pot changed out for a Bourns 3299w-501 500 ohm trim pot that has, what, 20 turns from 0-500 ohms for more precise adjustment of the output voltage, and each supply has added a 6 amp 120vac line filter (reducing noise so it doesn't disturb my TV watching/recording), but, each supply costs under $25 with free shipping.  Each supply drives one blade.  I don't put them in parallel anymore as it's easy to burn one up in parallel.  Then again I had to build my PCIE harnesses.  Also I add 4 digit LED voltage readouts to each as it's easier to tell if there's a problem.

Downclocking gives you 11% better efficiency. Since we're all working on small profit margins that is worth it imo.

Also all that work and gear to power 1 c1?!?  .. Why??

Not easier and cheaper to buy a Dell z750+bboard+cables for like 50-60$ and be done with?

[soy]

Okay, in the post he says the most efficient test was 575-590watts, 804-817GH/s so the best would be (575w/817GH/s) or .703w/GH/s.  The 1008GH/s test doesn't show a wattage.  His highest frequency test 1123GH/s drew 943watts or .839 w/GH/s.

Wish he had provided the watts at stock settings but yes, these are good numbers, better than mine.

I thought I did, but stock was 1008 / 802Watts @ .74v

The best was 805-821GH/s @ 575-600 watts between all 3 C1's I have. After that they start sucking Juice like my 3year old  .

I stopped using them as I'm concentrating on much more efficient miners for now (SP20's / S5's), but in a few days my $0.0779 / KWh kicks in and I'll put them to work in my office as they are quiet as heck, so the quiet factor I agree is much better at the trade off , of low hash rate/ high power usage.

On the other hand, now that I think of it, it's like an Avalon 4.1. I think those go down to 800GH/s @ about 550 watts and are very quiet. Almost the same I guess. I'll have to try one.

Okay.  So, $0.0779 will be your power cost.  Down here where it will get hot this summer my bill shows power to cost $0.075 but when I add in taxes but  not line charges I see $0.0805 but it's not all that clear with their adjustments.  

I worry about the heat damaging the ASICs.

To be honest, using the Kill-A-Watt, I don't see a big deal in cost savings when tuning for lower energy but I haven't tried the big jumps down.

Interestingly, with your numbers for C1 run at almost stock frequency and voltage, your 1008 / 802Watts @ .74v, compares well with these I took: after 1 hour at 250M/0760 I had 1008.57 / 818 watts for .811w/GH/s but the same unit at 2 hours showed 1002.88 / 819 watts for .816w/GH/s.  Ambient was 80°.  So reading of 802 watts is 98% of my 818watts.  That's only a 2% difference in supply efficiency.  

I'm using four 360 watt LED power supplies each modified with a heatsink added to the bridge rectifier, the one turn pot changed out for a Bourns 3299w-501 500 ohm trim pot that has, what, 20 turns from 0-500 ohms for more precise adjustment of the output voltage, and each supply has added a 6 amp 120vac line filter (reducing noise so it doesn't disturb my TV watching/recording), but, each supply costs under $25 with free shipping.  Each supply drives one blade.  I don't put them in parallel anymore as it's easy to burn one up in parallel.  Then again I had to build my PCIE harnesses.  Also I add 4 digit LED voltage readouts to each as it's easier to tell if there's a problem.

Downclocking gives you 11% better efficiency. Since we're all working on small profit margins that is worth it imo.

Also all that work and gear to power 1 c1?!?  .. Why??

Not easier and cheaper to buy a Dell z750+bboard+cables for like 50-60$ and be done with?

Yes.  Hadn't seen those.  I've been using these 12vdc 360watt supplies since my Mercury arrived.  

Okay, just bought one.  Looking at the price of breakout boards I think I'll go in and hard wire my cables for an initial test on an S3 to compare efficiency with my supplies.

What advantages do the reduced functionality breakout boards from GekkoScience have may I ask?

Also, is the z750p the same as a Compaq PS4060?  The schematic for the PS4060 shows rated loads for each voltage which add up to something between 600 & 700 watts and then there's the supply power load itself which would bring it up above 700.  So the PS4060 supply is rated for 25 amps on the 12vdc line or 300 watts.  So, it has less power where I want it than the 360 watt 12vdc power supply and isn't adjustable?

So, if these are good for 25 amps on the 12v line, and I use two of the 360w, 30amp supplies for an S3, then with the bboard and cables you say amounts to 50-60 bucks, I'd be spending 100-120 to do what I can do for $50 plus cables.  I don't NEED to add the filter and probably don't NEED to add the bridge recitfier heatsink nor the 20 turn trip pot instead of the stock 1 turn.  So, I probably made a mistake buying the Dell Poweredge 750w supply.

[soy]

Okay, in the post he says the most efficient test was 575-590watts, 804-817GH/s so the best would be (575w/817GH/s) or .703w/GH/s.  The 1008GH/s test doesn't show a wattage.  His highest frequency test 1123GH/s drew 943watts or .839 w/GH/s.

Wish he had provided the watts at stock settings but yes, these are good numbers, better than mine.

I thought I did, but stock was 1008 / 802Watts @ .74v

The best was 805-821GH/s @ 575-600 watts between all 3 C1's I have. After that they start sucking Juice like my 3year old  .

I stopped using them as I'm concentrating on much more efficient miners for now (SP20's / S5's), but in a few days my $0.0779 / KWh kicks in and I'll put them to work in my office as they are quiet as heck, so the quiet factor I agree is much better at the trade off , of low hash rate/ high power usage.

On the other hand, now that I think of it, it's like an Avalon 4.1. I think those go down to 800GH/s @ about 550 watts and are very quiet. Almost the same I guess. I'll have to try one.

Okay.  So, $0.0779 will be your power cost.  Down here where it will get hot this summer my bill shows power to cost $0.075 but when I add in taxes but  not line charges I see $0.0805 but it's not all that clear with their adjustments.  

I worry about the heat damaging the ASICs.

To be honest, using the Kill-A-Watt, I don't see a big deal in cost savings when tuning for lower energy but I haven't tried the big jumps down.

Interestingly, with your numbers for C1 run at almost stock frequency and voltage, your 1008 / 802Watts @ .74v, compares well with these I took: after 1 hour at 250M/0760 I had 1008.57 / 818 watts for .811w/GH/s but the same unit at 2 hours showed 1002.88 / 819 watts for .816w/GH/s.  Ambient was 80°.  So reading of 802 watts is 98% of my 818watts.  That's only a 2% difference in supply efficiency.  

I'm using four 360 watt LED power supplies each modified with a heatsink added to the bridge rectifier, the one turn pot changed out for a Bourns 3299w-501 500 ohm trim pot that has, what, 20 turns from 0-500 ohms for more precise adjustment of the output voltage, and each supply has added a 6 amp 120vac line filter (reducing noise so it doesn't disturb my TV watching/recording), but, each supply costs under $25 with free shipping.  Each supply drives one blade.  I don't put them in parallel anymore as it's easy to burn one up in parallel.  Then again I had to build my PCIE harnesses.  Also I add 4 digit LED voltage readouts to each as it's easier to tell if there's a problem.

Downclocking gives you 11% better efficiency. Since we're all working on small profit margins that is worth it imo.

Also all that work and gear to power 1 c1?!?  .. Why??

Not easier and cheaper to buy a Dell z750+bboard+cables for like 50-60$ and be done with?

Small profit margins, yes.  Just did a calculation:  average total TH/s speed of my miners according the pool, divided by the hashrate of my least productive miner, that quotient times that miner's wattage extropolated to a month, times the cost of power.  This would give me the cost for that miner to earn the monthly take, that derived from last payout divided by number of days times 30½.  If my month's btc were earned by miners running at the rate of my most inefficient, would it be more than the cost of electric?  So far yes, but I can't splurge on unnecessary power supplies or that goes away pretty quickly.

[thedreamer]

Wow man, you are waaay overthinking and building your power supplies/usage.

All you need is one Dell Z750, breakout board, cables and done. It can power 750W at 90+% efficiency for ever. They are VERY robust.
I run a few SP20's off them underclocked at 600 watts, but have tested them for a few hours with no issues at 900W, even peaked them at 1000W by accident at full speed.

You can get the Power supply for around $20, the breakoutboards for under $30, cables for a few bucks. NOTHING ELSE NEEDED.

On another note, the C1's are only worth using if you have cheap or free power, or if you want the quietest system possible. (I will be running a few in my office after my $0.779 / KWh price kicks in in a week. 

Until then, I don't use them constantly. I use mainly Spondoolies, as IMO they are the BEST miner on the market. Bar none.

[notlist3d]

Wow man, you are waaay overthinking and building your power supplies/usage.

All you need is one Dell Z750, breakout board, cables and done. It can power 750W at 90+% efficiency for ever. They are VERY robust.
I run a few SP20's off them underclocked at 600 watts, but have tested them for a few hours with no issues at 900W, even peaked them at 1000W by accident at full speed.

You can get the Power supply for around $20, the breakoutboards for under $30, cables for a few bucks. NOTHING ELSE NEEDED.

On another note, the C1's are only worth using if you have cheap or free power, or if you want the quietest system possible. (I will be running a few in my office after my $0.779 / KWh price kicks in in a week. 

Until then, I don't use them constantly. I use mainly Spondoolies, as IMO they are the BEST miner on the market. Bar none.

I personally don't include PSU's in my ROI always.  If you buy nice PSU's they will last longer then your miners being efficient. It is nice having a extra or two even around. 

I have some PSU's that have been around since GPU days.  Those have paid for their self a few times.   

[soy]

Wow man, you are waaay overthinking and building your power supplies/usage.

All you need is one Dell Z750, breakout board, cables and done. It can power 750W at 90+% efficiency for ever. They are VERY robust.
I run a few SP20's off them underclocked at 600 watts, but have tested them for a few hours with no issues at 900W, even peaked them at 1000W by accident at full speed.

You can get the Power supply for around $20, the breakoutboards for under $30, cables for a few bucks. NOTHING ELSE NEEDED.

On another note, the C1's are only worth using if you have cheap or free power, or if you want the quietest system possible. (I will be running a few in my office after my $0.779 / KWh price kicks in in a week.  

Until then, I don't use them constantly. I use mainly Spondoolies, as IMO they are the BEST miner on the market. Bar none.

So, the z750 supplies work under heavy load.  Typically a computer supply will claim a certain wattage capability and on the side list the current available on each voltage but don't supply that total wattage to any one voltage.

Worth using....  I'm retired living in the deep south, an emigre from Long Island's north shore.  I have no income aside from social security and mining.

So,  my calculation in the earlier post shows when income from my least efficient miner goes negative at current btc prices.  Easy enough to calculate when low btc value makes the miner go negative if the difficulty doesn't change much.  As long as the heat is getting exhausted and not loading down my AC there's no reason not to run my least efficient miner.  There's no reason to run it when it's take goes negative relative to power cost.

If I had the financial leeway to put the mined btc aside until payout halving next year, when I expect the value of btc to increase, I would.  But the power cost is such that I need to cash my mined btc in.  That negates any expectation of btc value increase for me on my mined btc.

[pekatete]

So, the z750 supplies work under heavy load.  Typically a computer supply will claim a certain wattage capability and on the side list the current available on each voltage but don't supply that total wattage to any one voltage.

In switched mode, the z750 has a single rail 12v @ 62.4A which equates to 748.8W. In standby mode it is 3.3v @ 5.5A which equates to 18.15W

[soy]

So, the z750 supplies work under heavy load.  Typically a computer supply will claim a certain wattage capability and on the side list the current available on each voltage but don't supply that total wattage to any one voltage.

In switched mode, the z750 has a single rail 12v @ 62.4A which equates to 748.8W. In standby mode it is 3.3v @ 5.5A which equates to 18.15W

Okay I was looking at this as it seems to be similar:

Abstract from google listing: COMPAQ PS4060 750W. HOT SWAP POWER SUPPLY. + 385V. 660uF. 100-240Vac controller. Primary board. 3.3V/ 40A. 12V/ 25A. ML4824-1. PFC / PWM ..

http://members.home.nl/a.k.bouwknegt/index_bestanden/Diagrams/PS4060%20single%20line.pdf
-------------------------

Are you sure the single 12v rail is suppose to supply 62.4A?  Are there other voltages?

[pekatete]

So, the z750 supplies work under heavy load.  Typically a computer supply will claim a certain wattage capability and on the side list the current available on each voltage but don't supply that total wattage to any one voltage.

In switched mode, the z750 has a single rail 12v @ 62.4A which equates to 748.8W. In standby mode it is 3.3v @ 5.5A which equates to 18.15W

Okay I was looking at this as it seems to be similar:

Abstract from google listing: COMPAQ PS4060 750W. HOT SWAP POWER SUPPLY. + 385V. 660uF. 100-240Vac controller. Primary board. 3.3V/ 40A. 12V/ 25A. ML4824-1. PFC / PWM ..

http://members.home.nl/a.k.bouwknegt/index_bestanden/Diagrams/PS4060%20single%20line.pdf
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Are you sure the single 12v rail is suppose to supply 62.4A?  Are there other voltages?

I am sure about the 12v @ 62.4A in switched on mode, but only 3.3v @5.5A in standby - at least that is what it is rated as.
Its a very robust PSU but if you are an engineer (or electronics' hobbyist), you could just pick the PSU up on its own, solder your brace on and run it from there (you'll have to switch it on yourself, plugging it on simply puts it in standby). That should save you a few $, but the gekko breakout boards (or jabber's) are fairly cheap inclusive. Your choice.

[soy]

What might be a consideration is that the design is robust and although rated for less on the 12v line it can provide more anyway.  

If so you'd be moving the switching supply design very far away from switching supplies usual comfort zone of 50% full load.  Expensive switching supplies can maintain efficiency across much of its range.  

Still, switching supplies, even out of their 50% comfort zone, are far ahead more efficient than non-switching power supplies.

Wasn't saying that correctly.  A 7812 will take an input voltage of at least 15 volts.  To get the 15vdc you want to take peak, (15v)(1.414)=21.21v; then for effective, no dropouts, take .86 of that (21.21v)(.86)=18.24vdc.That 18.24vdc will be after a bridge rectifier which is going to drop well over a volt under heavy current.  Then you want a step down transformer that will drop the 120vac down to 20vac.  At the regulator say it's 30 amps, 18v-12v=6v; (30a)(6v)=180watts dropped at the regulator.  Then the rectifier, lets say that's dropping 1½v, will be 45 watts.  Then there's the transformer inefficiency but even without its losses you're dropping 225watts for 12vdc@30amps.

So if our C1 is using 818 watts at the wall using an 88% efficient switching supply, our C1 is using 720 watts which is 60 amps at 12vdc.  Our non-switching supply example above would be dropping 450watts at 60 amps before transformer losses or 1170watts.