NAME
amas —
AMD memory address map
SYNOPSIS
amas* at pci?
DESCRIPTION
The amas driver provides read access to
the AMD memory map, which describes the location of physical memory.
One instance of this device is shared between all cores on a chip. This device is present on AMD processors of the 0Fh, 10h and 11h family.
The amas device can run in either
interleaved mode or in non-interleaved mode. 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. 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. If the request refers to memory present on a
different chip, the request is forwarded to the correct chip using the
hypertransport bus.
The amas device is configured by the BIOS
and kernel startup routines. If multiple instances of this device are
available, all should contain the same information.
SEE ALSO
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.
HISTORY
The amas driver first appeared in
OpenBSD 4.6.
AUTHORS
The amas driver was written by
Ariane van der Steldt
<ariane@stack.nl>.