If I remember correctly it was only the older S3s which had variable voltage Dogie.
I am going to retell some things I was told, but do not know these as facts myself, but what I remember reading when there was a big debate is being told the first "couple or few" batches of S3s did have it, but many of those first units stayed in the BITMINE(s) running with 0750 voltage and anywhere from 218 to 250 Frequency.
As they aged they were pulled but by this point the circuit had changed.
Then again when the S3+ came out same thing, many of those stayed in the BITMINE(s) and were not shipped and that there was quite a market saturation along with the fact the price started falling hard and the better performers were kept in the mines until they could begin exchanging those with the next revision (S4).
Even though it was released much later they worked on the S3++ as a private contract at the same time the S4 was being developed and slowly all of the S3 and S3+ best performers were blown off and sold. It wasn't an accident these were popping up occasionally, it was done by schedule, or "blocks" (no pun intended) of miners. Which those miners were well known because they knew what boards were used. The best for the best private contracts, and then they sold them used on ebay which really made it a random act who picked them up.
This is a factual story I lived:
I lived in Alabama for a few years working for a very small company who handled CNC Machinery. My main job(s) changed many times over the years there but my last few years I was basically a Purchasing Agent / Service Manager. I bought tons of computers because a couple went with every plasma cutting system we sold to run offline software. I made some great friends at a local PC shop. The place was fantastic for me, they loved my business and it was young guys like me at the time. This was the late 90s. They were a place you could go pick up an Athlon Thunderbird 1.6 chip and it would be only $10.00 over what you paid online. They were competitive and went for volume. Birmingham is a big city. They also had a self-service attitude. Bring your box in and work on it. Customers and employees would get together to figure out what was up.
Since I'd stopped travelling I was in there every night doing my thing. Since I was buying a lot of PCs and "all the fixins", monitors, printers, you name it, they liked my business. I was treated like an employee in the good ways. When a new batch of RAM came in whoever was interested could pick out what they wanted. I would spend all night going through sticks of RAM, popping them in my test rig to see what they could handle. Those were the ones I bought, at cost when it was my personal money. The same thing with CPUs. As long as I cleaned them up everything was fine. As far as temps, yeah they need to burn in, but speeds, well it does take a while to run benches, but not relative to everything else we had going on. Video cards, you name it, we cherry picked it. We had heat guns to put the plastic wrap back on the boxes. My customers owned machine shops and they always had a son or nephew in the scene and they made water blocks for us, it was a great, fun, learning environment. A problem always turned into a competition and if someone absolutely needed something fixed fast this was the place to go. If someone needed something to finish a job it would be pulled from a personal system if needed. I would have rather worked there but they didn't pay anything close to what I was making. Most of those guys would have worked for free if they could have the bills paid and get frozen pizzas and mountain dew. The technology was an addiction, add competition and that group of guys were teaching their vendors things. We put peltiers and watercooled anything that moved. I know for a fact some of the early articles on overclockers.com came from people working or doing work in that shop because it was nothing others would risk or even thought about at that point. It kept a lot of "kids" away from drugs by changing addictions, but the main point is you know the same thing happens at many manufacturers. Even BITMAIN.
There is not a moral to my story. I only wanted to get us thinking about how these things happen. How the best batches can be pulled, separated, and then distributed. BITMAIN is still a very new company in a technology area very few understand. Even at BITMAIN I bet young guns who are sick over the latest chips they get and cannot wait to try them in their latest rigs.
We all know the wafers have bad, better, best, blow your mind sections. You better believe the engineers and techs or whoever can get access are cherry-picking the hell out of it. They get a potentially huge contract from a big name and send some samples, what are they going to send? When the techs who pooled their money to buy 2000 BM1384 chips are finished testing, they swap the chips for another batch, and so on, until they know their home rigs are badass. The best of everything they can get from work.
Hey, its a perk. Us in the field are going to get what we were sold, it isn't like we are being done a disservice. I think the disservice comes from how long they stay in the BITMINE(s).
I am picking on BITMAIN here but I do not mean to do so in this case. This goes on anywhere and everywhere until the company gets so bureaucratic, people mature, inventory gets locked down, people lose interest, get married, have kids, etc but even then. There will always be a new batch of kids, with that burn to have the best and the fastest who will find a way. Not to mention if you are the engineer(s) with the keys to the closet.
While I am way off topic, I wanted to propose some other things which fit in what we see as random being perfectly predictable.
I never think it is unusual for someone to get one of the sickest machines, or a batch of them and the next batch be normal.
One of the best things that can be said about things happening this way is I know I always have and will treat my components like gold. I push them hard on the bench to see what they can do but follow instructions and always ask so many questions I'll get on your nerves. I never returned anything in bad condition. IF it was in bad shape it was because I'd seriously fucked up. As in sealing a processor in a mobo socket so well for condensation protection I couldn't get it back out and eventually broke it in half removing it.
These little aluminum heatsinks bitmain is using on the S5+ were going on video cards to cool the memory and processor 20 years ago. We used plexiglass to hang servers on the wall or build cubes of aluminum and have the equivalent of a huge network the size of an end table, watercooled with a volkswagen radiator on the back and plasma power supply pumps closing the loop. We filtered the water, etc, but the RAM, CPUs, Vid cards, hard drives, and anything else which can be cherry picked, was cherry picked.
Many of those mods were sold, and then sold used, again and again. So it was never unusual to hear about someone saying they bought this "kit" that had higher 3Dmark scores and an unusually fast this or that. It was usually something someone had built, played with for a month, sold and were building a new one with the next greatest technology.
Those were some fun nights