the following is a C/P from the link below....it involves 7 man EGTBs, which are not available to the public yet, despite almost seven years since this was discovered.....the complete 7 man EGTBs when completed are expected to take at least 100 TB of storage, but from what I understand, the format is still being developed.....but sooner or later, it will be done, then onward to the 8 man EGTBs!!!
PS: for me to load all the 6 man EGTB "indexes" on a fast machine takes almost 2 minutes (they consume about 2GB of RAM), so 7 man EGTBs will take hundreds of GBs, and a long time to load, I suspect!!!...but who knows, it was not too long ago that people had to wait like 20-30 minutes for the 6 man EGTBs to load all the indexes.....
Black to play, White wins in 517 moves Marc Bourzutschky and Yakov Konoval, May 2006
Incredible news from the wizards of 7-men endgames, Marc Bourzutschky and Yakov Konoval. Barely two months after breaking the 300-move barrier in tablebase endgames (see item 311) they have now found a position where it takes White 517 moves to win (convert to a winning sub-endgame) with best play by both sides: White and Black always aim for the fastest and slowest conversions, respectively. At the discussion forum TalkChess Bourzutschky writes: "This was a big surprise for us and is a great tribute to the complexity of chess."
"Even deeper 7-man endings may exist, but I doubt it," writes Bourzutschky. But also: "That such a great depth is still possible with so much firepower on the board suggests that even deeper endings may arise with 8 pieces, perhaps in krnnkbbn. This ending could be generated with 64 GB of RAM in a few months on a fast single CPU machine and about 5 terabytes of storage. Any takers?"
Here are those moves. As always, only-winning moves have an exclamation mark.
NB: Games over 300 moves cannot be entered in ChessBase, but the moves can be played over on the Palview board on the left. And as Bourzutschky notes, Scid also manages without a hitch. You can copy & paste the moves into it; it's not even necessary to remove the !'s - they show up, too.