13.2.1 for XO-1 using external SD card slot

[James Cameron]

Announcing an unsigned early build of 13.2.1 for XO-1 using external
SD card slot.

The XO-1 has 1GB of NAND flash with jffs2 filesystem.  After many
years of service the NAND flash will have slowed down [1].

The XO-1 has a 433 MHz Geode processor.  The processor is used to
compress and decompress data stored on NAND flash.

The XO-1 has 256 MB of RAM.  11 MB is consumed by jffs2 filesystem log
structure.  During read and write, extra memory is used temporarily
for compress and decompress.

The XO-1 has an external SD card slot.  Some don't work well, but most
do.

SD cards have increased in performance, increased in capacity, and
decreased in cost.

Therefore using an SD card instead of NAND flash should increase I/O
performance, decrease processor time, and increase available memory.


Would you like to try it?

You need an XO-1, an SD card of 4GB or more, a USB drive of 1GB, and a
download of 585 MB.

http://wiki.laptop.org/go/11233 has the instructions.

This build is 13.2.0 plus new firmware, plus new kernel with wireless
fixes, plus driver for new camera, and packaged for use with an SD
card, not internal NAND flash.  The NAND flash is not touched.

Do not remove the card while the laptop is running.  The laptop will
hang if the card is removed.  The data on the card may be damaged.

In testing so far, this build boots a little bit faster than 13.2.0.

Measurement methods suggested:

1.  subsequent boot time to journal ready,

    (boot first time, enter name, select colour, wait for journal icon
    to colour, shutdown, press power button and begin timing, wait for
    the journal icon to colour and end timing).

2.  initial startup time for Browse activity,

    (boot once, open Browse, quit Browse, reboot, wait for journal
    icon to colour, switch to journal, start Browse journal entry and
    begin timing, wait for rendering and end timing, quit Browse),

3.  subsequent startup time for Browse activity,

    (prepare as above, then start Browse journal entry and begin
    timing, wait for rendering and end timing, quit Browse)

A further performance gain is to add a swap file to the SD card, which
in my tests using Sugar can free up to another 30 MB.

--

Footnote:

1.  no analysis is available for how much slow down has happened, but
a timing of scan-nand and copy-nand firmware commands should be an
effective measure:

ok t( scan-nand )t

press the escape key while the scan is in progress, then read off the
result in milliseconds,

ok t( copy-nand u:\32013o0.img )t

note this destroys all data on the laptop.

-- 
James Cameron
http://quozl.linux.org.au/