[GTALUG] war story: memtest86+ vs. UEFI

[Lennart Sorensen]

On Mon, Mar 30, 2015 at 01:24:54PM -0400, D. Hugh Redelmeier wrote:
> Summary: it seems that memtest86+ won't run under UEFI.  You need to
> switch to "legacy" boot and use an appropriate CD/DVD/USB stick to
> supply memtest86+.

Yes I see memtest86 does work with UEFI, but memtest86+ does not.
But memtest86 seems to have stopped being open source at version 5 which
is when they added UEFI support as far as I can tell.

> I often run memtest86+ when I get new RAM.  This increases my confidence 
> that the RAM isn't busted and is compatible with the machine it is 
> installed in.  Running it overnight seems long enough without interfering 
> with my use and enjoyment of the computer.
> 
> I even run it on a brand-new machine as one of the confidence building 
> measures.
> 
> Well, that's what I used to do.  I've not taken the time to do it 
> recently.  But I wanted to run it last night because I bought some 
> (mislabelled!) RAM at the NCIX warehouse sale on Saturday.
> 
> Ubuntu lets you install memtest86+ as a package (it may be a default
> package, I don't know).  But you cannot run it under Ubuntu, you have
> to boot into it.  When you install the package, it adds a grub entry
> to let you boot into memtest86+ instead of Ubuntu.  Yet on my machine
> there was no such entry.  Reading the script that generates the entry,
> I found that memtest86+ must be booted in 16-bit mode, i.e.
> old-fashioned BIOS, and not UEFI.  So the script doesn't bother to
> generate the entry on a UEFI system (silently).
> 
> To run memtest86+, you have to switch the system firmware to use
> "legacy" booting (old-fashioned BIOS/MBR).  On my machine, you cannot
> enable both MBR and UEFI booting: you need to choose one.

Hmm, interesting.  I think every machine I have ever used supported having
both at the same time and you could choose which it should try first.

> Once I switched to legacy booting, I could no longer use the Ubuntu on
> my hard drive since it was set up for UEFI.  I used a Ubuntu
> installation DVD -- it has an early option for running memtest86+.

The new machine I got at work actually lets you pick UEFI or legacy for
each boot device in the system, which is rather nice of it.  Makes things
much simpler.

> It turns out that Fedora 21's live/install image has a newer
> memtest86+ than Ubuntu 14.04: 5.01 vs 4.20.  The newer one lists the
> DIMMs or SODIMMs present on the system.

5.01 certainly is the latest version.

-- 
Len Sorensen