Boot Linux, NEVER Windows, after a memory upgrade!

Stupid me ... I should know better ...

After a memory upgrade on my HP Pavilion dv9000z notebook (see the following, related "review" below) failed to start Linux correctly, I stupidly assumed it could be -- even though this is virtually impossible -- somehow something to do with the Fedora Core 6 x86-64 (specifically Linux kernel 2.6.20 Fedora build 1.2925.fc6) system was booting, configured, etc... So without thinking, I figured I'd just boot Windows to see if I had the same errors and faults, etc...

Stupid me ... I should know better ...

You see, when Linux systems boot, they boot the disk read-only, meaning they do not write to the disk at all -- not until very late into the boot process. And if not everything looks correctly -- let alone if the init (initialization) process or one of its sub-processors or init scripts don't remount the filesystems as read/write (normal usage) -- the disk will not be corrupted.

All Microsoft OSes (including DOS-based like 95/98/Me and NT-based like 2000/XP/Vista), on the other hand, boot read/write from virtually sector #2 (after the master boot record, MBR, on PCs, although NT 5.1/6.0 aka XP-2003/Vista often does a series of reads/writes to hidden sectors in the MBR after sector #1). So what I got was a nice and toasted C: drive as a result of my memory issues.

Thank you Microsoft! No, I should know better, this is on me. And now you know.

Boot Linux never Windows when you upgrade your memory. Your memory may have compatibility issues resulting in corruptions and you do not want blocks from memory flushed to disk when memory is corrupted due to hardware issues! Linux doesn't mount its filesystems read/write until late in the boot process, assuming no issues (much less it doesn't write to "hidden" areas of the disk label aka partition table -- and even MD/LVM avoid doing such until later in the boot process too), and will "crap out" to a prompt with anything still mounted "read-only" if there are any issues.

For those that don't have Linux installed, you can use a Linux "Live CD" (or DVD) like Knoppix (Debian) or other distro (like the new Fedora Live) CD/DVDs.

Luckily ... I backup my C: drive every 2 weeks or so. ;)

You see, it only wiped out my small, 32GB NTFS C: partition. I learned long, long ago (I've been using NT 3.1 since the original Beta in 1992-1993, and OS/2 with HPFS before, as well as after, that) that keeping the C: drive small has saved my bacon so many times. I put everything non-system/non-boot (MS terminology: system=NTLDR bootstrap including any NTBOOTDD.SYS driver, boot=NTKERNEL.EXE and C:\WINNT directory -- yes, the system=boot and boot=system seems opposite, but that's MS' official NT -- system then boot -- terminology for start-up) on the D: drive -- data, programs, even relocate profiles and Documents to D: via registry changes for my user(s) -- everything except system/boot (and that would include driver/hardware programs installed on C: too, because they could be used at boot). I then I keep a dd image (a raw, sector-by-sector, image) of that C: drive on an external FireWire/USB hard drive (on a Linux Ext3 filesystem), which I re-dd about every 2 weeks so I can recover it if NT (including newer 2000/XP) self-toasts.

Related review of PNY 1GB PC2-5300 (DDR2-667) SO-DIMM (CompUSA SKU 340840) ...

First off, PNY's web site's own memory configurator does NOT yet even
offer ANY HP Pavilion 9000 series choices (only through the 8000 series),
neither Intel Core (dv9000t series) nor AMD Turion (dv9000z series).
But stupid me, I didn't check the web site before buying, and figured
anything that says PC2-5300 (aka DDR2-667) must be at least JEDEC
PC2-5300 compliant.

I could NOT get the SO-DIMMs to boot my HP Pavilion dv9000z without
throwing out errors. At first, I thought it might be a memory controller
issue because each 1GB SO-DIMM had 16 ICs, whereas the original 512MB
SO-DIMMs had only 8 ICs per unit. But then not even a single 1GB SO-DIMM
would work correctly on its own (yes, the AMD Socket-S1 does support
single channel use, including on the newer Mobile Sempron / Turion x2
systems). I reseated the SO-DIMMs a half-dozen times to no avail, even
though putting the originals back in a half-dozen times worked
flawlessly each and every time so it wasn't the SO-DIMM sockets.

There's clearly an issue with the IC sizing, bit-width/IC number or
something else and they are possibly not even fully JEDEC PC2-5300
compliant -- not even for a single SO-DIMM on its own. I thought
everything DDR2-667 these days was JEDEC PC2-5300 and there were no
platform-specific issues unlike DDR2-800 (as JEDEC PC2-6400 is far less
standardized), but I guess not!

Again, since PNY's own memory configurator (as of March 2007) doesn't
even offer any HP Pavilion 9000 series in its list, I'd *AVOID* any
PNY PC2 (DDR2) SO-DIMMs for the time being. I wouldn't even try the
2GB kit with 2 pieces for $10 more (SKU 344987)

And yes, the original memory (2x512MB) is back in this very unit, working flawlessly.