Raspi driver is about 50 Ohm pmos transistor resistor - with 1kohm you'll get shitty waveform. Just terminate with 50 Ohm and it will work!
Inputs are CMOS, but currents goes in of course when you recharge capacitors. However input levels are sampled using buffer amplifiers (like operational/differential amplifiers), so logic levels may be any you like, just sharp enough edges. Somewhat similar to SSTL... This was built to be able to level-shift using just STRINGS!
You can build devices! GREEN LIGHT! Code that I posted works.
Garbage computation (internal logic misconfigured):
0.596 V 0.541 A 87 Mhz 1 GH/s 0.32 W 0.31 W / GH/s
0.596 V 0.326 A 44 Mhz 0.5 GH/s 0.2 W 0.38 W / GH/s
0.596 V 0.502 A 80 Mhz 0.93 GH/s 0.29 W 0.32 W / Gh/s
0.596 V 0.853 A 155 Mhz 1.8 GH/s 0.5 W 0.282 W / GH/s
Please note that garbage computation consumes LESS POWER than when we compute SHA256 (right now I do not read data FROM chip as have to solder level shifter, but can have conclusions based just on power consumptions. So I can estimate frequency when it falls down:
0.596 V 0.673 A 86 Mhz 1 GH/s 0.4 W 0.4 W / Gh/s
0.596 V 1.049 A 145 Mhz 1.68 Gh/s 0.62 W 0.37 W / Gh/s
0.596 V 1.516 A 235 Mhz 2.73 Gh/s 0.9 W 0.33 W / Gh/s
0.596 V 2 A 320 Mhz 3.72 Gh/s 1.19 W 0.32 W / Gh/s
0.596 V 1.931 A 400 Mhz 4.65 Gh/s 1.15 W 0.24 W / GH/s (please note - HERE WE DO NOT COMPUTE USEFUL HASHES LIKELY!)
Then - voltage sweep (limited to 3 Amps now):
0.65 V 2.56 A 410 Mhz 4.77 Gh/s 1.67 W 0.35 W / Gh/s
0.687 V 2.997 A 467 Mhz 5.43 Gh/s 2.06 W 0.38 W / Gh/s
0.545 V 1.52 A 280 Mhz 3.26 Gh/s 0.83 W 0.25 W / Gh/s
0.5 V 1.07 A 216 Mhz 2.5 Gh/s 0.54 W 0.21 W / Gh/s
Clock is set by using internal SLOW oscillator programmed with code:
{0xff,0xff,0xff,0xff,0xff,0xff,0xff,0x0f}; - with code 0x1f not works
But clock likely would be different.
Now I have to test read-back and test real error-rates, as there can be up to 30% and it won't be noticed just with power consumption, however 80% error would. That's it... Very little chances still exists that we fail (as models match with practice is very close, close to measurement limitations of my equipment, I am amazed really), but real life differs from theory (i.e. I wouldn't loose bet if everything would go as expected :-).
By the way board isn't bad at all - with 1 W we had 46 degrees board temperature with 26 degrees in a room... and it lives
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USB-stick could be nice product with these chips!