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MXT Support Patch for Linux
Overview
Memory eXpansion Technology (MXT) is a hardware
technology for compressing main memory contents. MXT
effectively doubles the amount of memory.
For example, 512 MB of installed memory appears as 1 GB.
MXT is transparent to CPU, I/O devices, application software
and device drivers: no software changes are needed.
The first commercial grade memory controller chip incorporating MXT,
called Pinnacle, will be available from IBM's licensee ServerWorks Inc.
Several computer vendors are working to incorporate this chip in to their
motherboard designs, as well as designing new memory controllers
incorporating main memory compression.
A corner case exists when 2 to 1 compressibility assumption breaks
down, for example when memory contains already compressed data.
The MXT support patch must be applied to the Linux kernel
to deal with this condition. The document
/usr/src/linux/Documentation/mxt.txt
describes MXT and the support patch in detail. The 2.4 support was
implemented as a device driver module and a
less than hundred lines of a kernel patch.
(Please note that MXT is a hardware feature. An erroneous news
article has been published in a trade magazine which suggested that
software downloaded from this website will double the memory size of
your plain old
computer. This is not possible.)
Why do I need MXT?
Simply put, MXT buys you price/performance.
You can either cut your memory costs by half. Or you can increase
performance since with MXT the effective memory size is typically twice
the installed memory size.
Watch the demonstration video (2.1 MB file)
How to buy MXT based servers?
Please visit IBM xSeries 330MXT
web pages
for more information.
How to get the MXT support software?
- RedHat 7.2 supports MXT (10/2001)
- RedHat 7.1 kernel upgrades support MXT hardware (10/2001)
- Linux 2.4:
Patches are available.
Please check the MXT home page
for the patches.
Publications and Documents
-
IBM Journal of Research and Development
special issue
Vol. 45, No. 2, 2001
- MXT BIOS Specification: BIOS EBDA area will contain an MXT signature and table
identifying
hardware characteristics. Format of this table is detailed in this document.
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