The NVRAM in this case is the long term storage RAM.. the 'storage
RAM' in normal Palms; the goal of it was that when your battery runs out,
you don't lose your data. (The drive for this came from the Treo side more
than anything I think .. people are used to not losing their address book
in a cellphone when it runs dry. For PDAs, people were mostly trained to
hotsync, but the NVRAM is still nice here.) For this posted goal it works
pretty well.. if I lay down my Treo 650 for a month and pick it up, it'll
be perfectly fine after charging up.
Its all the bugs they introduced along side the NVRAM that makes
us all mental :)
Any modern NVRAM usually comes with a posted flash limit; look at
your flash keychains .. the usual number is "it'll go bad after 10,000
flashes" say. The BIOS on such devices will make it so when the OS says
"write to block 10 with value foo", the BIOS will map block 10 to some
random place on the flash chip, thus spreading out the writes to any given
cell, so that that "10,000 writes" is actually more .. ie: Otherwise your
10,000 writes woudl end up (say) at the beginning of the chip and it'd go
bad, while th eend of the chip never got hit once. Instead it all gets
used more or less evenly, given sufficient activity.
Anyway, NVRAM is expensive so they don't use big lots of it; and
with the write limit, many devices use anintermediate cache chip; and RAM
is expensive.. so when the device is designed they put in (say) a 32MB RAM
chip, with so much for the OS, so much for storage cache, so much for
runtime RAM, screen RAM and so on.
When you ask the device how much free storage it has, it will
report how much storage is available in NVRAM (the long term storage pool
that we're all used to.) Since applicatoins have bene around for years,
and unless rewritten recently (very few), they are not aware of all the
NVRAM voodoo under the hood. So the apps might say "hey, how much space od
I have.." and get told 100MB say (T|X). In reality, the device has a cache
chip inbetween though, with say a MB or 2MB free at that instance. What
happens when the application then says "I've got 100MB fre,e I need 3MB to
hold a big image file, so hand it over" but the OS can only provide 1MB
(cache is otherwise full) ...
Or consider .. traditional Palm OS you can open and access a
database instantly.. its all just RAM. Now when you open a database, the
OS sneakily makes a copy from NVRAM into cache, and lets you work there.
But isnce cache is small, it generally can't go copyin in the whole
database.. it'll copy in parts the application is asking for (I'm guessing
here.) So what happens when an application is seeking back and forth
through a database.. lots of copying to/from the cache (not really fast.)
Or what happens when you open a file and it gets sucked into
cache, and you chang some stuff, and gthe device crashes and resets. All
that data the app _thinks_ is saved, is actually in cache .. and lost.
(Multiply by what happens if data is relational, and some gets saved to
NVRAM and some is still in cache.. then the app suddenly has half baked
data, when it thouht it was all good pre-crash.)
Plus the various bugs in the OS that just don't handle things
right in lots of cases.
Factor in all the other changes ot the OS at the same time (the
data mangler bugs, with the new PIM applications, which tie into all this
stuff.)
.. and so on.
Its a good idea, that maybe wasn't implemented right,, and
certainly the implementation process was all bad (not involving developers
to do big testing and handle things wisely)..
jeff
On Wed, 2 Jul 2008, Bert Latamore wrote:
# Jeff,
#
# Interesting. The whole NVRAM thing in the later Palms is actually one of the reasons I stay with my T3, which doesn't have that. They put in just enough NVRAM to create all kinds of problems, and not enough to do much good. For those who don't know what we are talking about, NVRAM is non-volatile RAM, which means that whatever is in it does not get wiped out of you do a hard reset, at least in theory. That would be great if all the memory, or at least a big chunk of it, was NVRAM. BUT in fact only a very small amount is in NVRAM in these devices. Which means that most of your datda and third party apps (if you have many of them) are in normal RAM. Which means you had better back up your PDA just as often as I back mine up (to two SD cards plus a hot sync a day, is what I recommend. I do
one SD card around noon and the other one before I go to bed at night.) And on the other hand NVRAM somehow ended up creating all kinds of problems and complications that
# I don't see in my T3. So what good did it do to users? Not much that I can see, unfortunately.
#
# Bert Latamore
# Freelance Editorial Consultant
#
#
#
# ----- Original Message ----
# From: Jeff Mitchell <***@skeleton.org>
# To: shadow-***@yahoogroups.com
# Sent: Wednesday, July 2, 2008 10:38:39 AM
# Subject: Re: [shadow-discuss] Re: Another Disappearing List Problem
#
#
# On Wed, 2 Jul 2008, pwd10033 wrote:
#
# # So the problem is either with the list file or with something else in
# # Palm OS (or other installed apps?) that is causing the file to
# # disappear, not only from the Shadow Plan launch screen but from the
# # file system itself!
#
# It is probably the OS itself though I'm going from old memories;
# with the first rounds of NVRAM devices (I think the E2 is among them)
# there were approximately a million bugs in the OS and I'm fairly certain
# the vanishing file thing was among them. (ie: The NVRAM devices have a
# cache, since writing to NVRAM 'uses it up' over time.. thus the device
# copies accessed file chunks to cache RAM where applications use it, and
# then the device pushes the cached changes back out to NVRAM for permanent
# storage. This is a pretty weighty change to the OS and 3rd party
# developers were not involved or informed about it, and as such a lot of OS
# bugs appeared.. thousands of emails here are about it in one form or
# another :)
#
# Anyway, I don't think I ever tracked down the particulars of this
# one .. some sequence of events the NVRAM caching mechanism doesn't like
# and gets confused about and just loses data (PEACHY!)
#
# Creating a new file of an existing file is easy, so let us hope
# that cures your list..
#
# i) On the handheld, use the Duplicate List function in the file
# selection screen to create a new nearly identical list.
#
# ii) On the desktop, you can do a Save As and create a new xml
# file, and then ask the desktop to upload it and do a sync.. entirely
# new list with same text content.
#
# jeff
#
# --
# If everyone would put barbecue sauce on their food, there would be no war.
#
#
# [Non-text portions of this message have been removed]
#
#
# ------------------------------------
#
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--
If everyone would put barbecue sauce on their food, there would be no war.