AMAS(4)

💅 AMAS(4) — AMD memory address map, but make it make sense

okay so bestie, welcome to the manual page for amas — the AMD memory address map driver. it lives in the Kernel Interfaces Manual, and it's genuinely so much cooler than the name suggests. no cap.

✨ SYNOPSIS ✨

amas* at pci?

that's it. that's the whole vibe. it attaches at pci? — and yeah, the * and the ? are doing their little wildcard thing, we love that for them. 🎀

---

🌸 DESCRIPTION 🌸

so the amas driver gives you read access to the AMD memory map, which is basically the map that describes where all your physical memory lives. it's giving "you are here" but for DRAM. 🗺️✨

one instance of this device is shared between all cores on a chip — like, one map, everyone reads it, it's giving communal notes app energy.

this device is present on AMD processors of the 0Fh, 10h and 11h family. older gens, but iconic in their own right. 💜

the amas device can run in either interleaved mode or non-interleaved mode. and bestie, interleaved mode is where the plot thickens: in interleaved mode, the physical memory addresses are rotated across each chip. 🔄

amas sits between the CPU cores, the DRAM controller and the HyperTransport bus. literally main character positioning. so when a CPU requests a memory page, amas decides if the request is serviced from memory local to the chip — in which case it normalizes the address and passes it on to the DRAM controller. but if the request refers to memory present on a different chip, the request gets forwarded to the correct chip using the HyperTransport bus. like a little mail carrier for addresses fr fr 📬

the amas device is configured by the BIOS and kernel startup routines. and here's a cute lil fact: if multiple instances of this device are available, all should contain the same information. consistency slay. 👑

---

🦋 SEE ALSO 🦋

• pci(4) — go read it, iykyk
• BIOS and Kernel Developer's Guide for AMD Athlon 64 and AMD Opteron Processors, Publication # 26094, pp. 66–80, February 2006.
• BIOS and Kernel Developer's Guide (BKDG) For AMD Family 10h Processors, Publication # 31116, pp. 158–167, March 2008.
• BIOS and Kernel Developer's Guide (BKDG) For AMD Family 11h Processors, Publication # 41256, pp. 109–114, July 2008.

like, the reading list is real. get into it. 📚

---

🧚 HISTORY 🧚

the amas driver first appeared in OpenBSD 4.6. a legend from day one. ⭐

---

🫶 AUTHORS 🫶

the amas driver was written by Ariane van der Steldt <ariane@stack.nl>. we stan. 💖

---

ok that's the whole page bestie, go forth and understand your physical memory map 💅

Debian · July 16, 2013 · AMAS(4) — mwah, that's the sign-off, catch you on the next man page 🎀✨