What is the meaning of "El Pnei Orech Amos ha'Me'ah Pesach ha'Tzafon"?
Rashi: To the opening of the chamber that faces north, to Chatzer ha'Chitzonah. The chambers occupy 100 Amos from east to west, and the width from the wall to the chambers of 50 Amos from north to south, like it says below (8). Also refer to 42:4:5:1.
Radak citing Targum Yonasan: One gate open to the north.
Vilna Gaon: There were 100 Amos from the opening until the end of the chamber.
Malbim: From there he entered Lishkas ha'Me'ah. Also it was open in the south. The width of the opening was one Amah, opposite the place where he went out to Lishkos ha'Esrim via the open Amah. Its primary opening was to the north ? from there he goes out from Lishkos ha'Me'ah to the north, opposite the Ritzpah. The openings were close to the east. "El Pnei Orech" teaches that the face is always to the east ? there begins the length of 100 Amos, and there was the Amah opening of Lishkos ha'Me'ah, and opposite it the primary opening in the north. He entered the Amah opening in the south, and passed through the chamber of 50 Amos to the northern opening, opposite the Ritzpah of Chatzer ha'Chitzonah. 1
Malbim (1): Chatzer ha'Chitzonah opposite the Heichal and Ulam was 113 from south to north. Lishkos ha'Esrim occupied 20 Amos, Lishkos ha'Me'ah were 50 wide, and there was a path of 10 Amos between them; 33 Amos remained. In the four corners of Chatzer ha'Chitzonah were Chatzeros Keturos (46:22) 40 long and 30 wide. From the west, 13 of the 40 were opposite Achorei Beis ha'Kapores, and 27 were opposite Lishkos ha'Me'ah. There were three Amos between them and Lishkos ha'Me'ah (for 33 remained from Lishkos ha'Me'ah until the end, and Chatzeros Keturos were 30 wide). After Chatzeros Keturos began the Ritzpah and the chambers on it. It was four wide next to Kir Chatzer ha'Chitzonah, so it was at most 29 from Lishkos ha'Me'ah. Perhaps the gap was less, if the chambers of Lishkos ha'Me'ah were wider than the Ritzpah.
Why does it say "ha'Me'ah" (with the prefix Hei ha'Yedi'ah)?
Radak: This is because it was mentioned above (41:13).
What do we learn from "veha'Rochav Chamishim Amah"?
Rashi: He sees the width of 50 Amos until the northern wall of Chatzer ha'Chitzonah.
Radak: This is like it says "v'Al Pnei Sha'ar ha'Ison Al Lifnei Ulam ha'Sha'ar ha'Penimi Chamishim Amah" (40:15).