Using memtest86 with UEFI

[Robert Heller]

At Thu, 14 Apr 2022 17:57:12 +0200 "Ubuntu user technical support,? not for general discussions" <ubuntu-users at lists.ubuntu.com> wrote:

> 
> On Thu, 14 Apr 2022 at 17:33, gene heskett <gheskett at shentel.net> wrote:
> >
> > That line of users is already quite long, Liam, I am in it too. If
> > memtest86 is incompatible with UEFI, or vice-versa, that needs to have
> > been fixed, 6 years ago?
> >
> > Why has it not been?
> 
> If it is a 16-bit binary, that might be why. I know that people have
> problems with early MacBooks that have 32-bit UEFI firmware but 64-bit
> processors. No normal 32-bit-only PCs had UEFI, so all Linux distros
> expect UEFI to be 64-bit and 32-bit machines to not be UEFI. The
> combination of 2 things that should not be found together apparently
> makes it hard to install Linux on certain now-old MacBooks.
> 
> More info, merely as an example:
> https://mattgadient.com/linux-dvd-images-and-how-to-for-32-bit-efi-macs-late-2006-models/
> 
> If 32-bit UEFI is a problem, then a 16-bit UEFI payload is probably
> next to impossible. :-( And if they made memtestx86+ fully 64-bit it
> would stop working on older 32-bit and BIOS-only PCs.
> 
> Damned if you do, damned if you don't. :-/
> 
> > Take care abd stay well, Liam.

memtest86 appears to a somewhat strange beast:

sauron% file /boot/memtest86/memtest.bin 
/boot/memtest86/memtest.bin: DOS/MBR boot sector
sauron% file /boot/memtest86/memtest.img 
/boot/memtest86/memtest.img: DOS/MBR boot sector
sauron% file /boot/memtest
/boot/memtest: DOS/MBR boot sector
sauron% fdisk -l /boot/memtest
Disk /boot/memtest: 161 KiB, 164864 bytes, 322 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x52c3ebe2

Device         Boot    Start        End    Sectors  Size Id Type
/boot/memtest1      12124343 3284782550 3272658208  1.5T 5a unknown
/boot/memtest2       6778473    6778473          0    0B 4c unknown
/boot/memtest4             0          0          0    0B  0 Empty

Partition table entries are not in disk order.


> 
> You too!
> 
> 
> 

-- 
Robert Heller             -- Cell: 413-658-7953 GV: 978-633-5364
Deepwoods Software        -- Custom Software Services
http://www.deepsoft.com/  -- Linux Administration Services
heller at deepsoft.com       -- Webhosting Services