[GTALUG] OT: UEFI and Windows mysteries [was: New Deaktop PC -- To Run debian Linux - PCPartPicker Recipe]

[Bob Jonkman]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hugh wrote:
> UEFI firmware usually (but not always) includes a CSM
> (Compatibility Support Module) to emulate BIOS for the sake of old
> OSes.  If present in the firmware, it usually can be enabled or
> disabled in the firmware config menus.  As far as I know, all
> stand-alone motherboards have a CSM (Win 10 tablets often do not).

I recently repaired an Asus laptop in which the firmware had no
setting for compatibility. I was alarmed, but it worked fine with
Ubuntu 17.10, although not the orginal Win10 on the hard drive that
came with it.

It always booted to the firmware config screen, and wouldn't load the
OS (Win10); wouldn't load the .EFI file from the system32 folder. I
tried to swap in an old drive for Win7, and Windows booted but refused
to behave properly, as I suspected it might -- WiFi drivers didn't
exist in Win7 for that model laptop. So I swapped the original
non-booting drive back, and mysteriously everything worked again...
*Now* the .EFI files loaded, and the laptop was back to normal.

I don't much like the new, low-cost hardware. I've also had other
problems on an ultra-cheap desktop with minimal firmware settings.
Wouldn't dual-boot Ubuntu (probably 16.04) unless I switched it to
Compatibility Mode, but then it wouldn't boot Windows. Had to leave
detailed instructions for the client on switching in and out of
Compatibility Mode...

I welcome further off-topic insights, although the list moderators may
not be so tolerant.

- --Bob.

On 2018-03-28 03:04 PM, D. Hugh Redelmeier via talk wrote:
> | From: Lennart Sorensen via talk <talk at gtalug.org>
> 
> | On Wed, Mar 28, 2018 at 09:50:42AM -0400, Steve Petrie, P.Eng.
> via talk wrote: | > *** I know that PS/2 is an ancient interface. I
> only chose PS/2 because it is my understanding that a PS/2 keyboard
> and mouse combination is better supported and earlier, during the
> actual Linux boot process, than a USB keyboard and mouse
> combination. So PS/2 keyboard and mouse offer more liklihood of
> functionality when there are Linux boot problems. | | The BIOS
> emulates PS/2 for USB mouse/keyboard just fine and should | not
> cause any issues.  But yes it is slightly more complex to use a |
> USB device.  I don't remember the last time I dealt with a PS/2
> device. | I don't miss them.  I don't think I have had a problem
> with a USB keyboard | for a decade.  USB mice are never a problem
> since you never need a mouse | unless the system is actually booted
> normally, so only for a keyboard is | PS/2 at all interesting.
> Well unless you are one of those extreme gamers | that care about
> the potentially lower latency of PS/2 mice over USB mice.
> 
> (I may have some of this wrong.  These details are considered too 
> complicated to explain to users so we are just supposed to assume 
> everything just works.)
> 
> - firmware isn't BIOS these days.  In fact, that was a misnomer on
> the PC since day 1.  It's a carry over from the CP/M days on Intel
> 8080 processors.  Now it is called, uhh, firmware.  Or UEFI
> firmware.
> 
> - UEFI firmware usually (but not always) includes a CSM
> (Compatibility Support Module) to emulate BIOS for the sake of old
> OSes.  If present in the firmware, it usually can be enabled or
> disabled in the firmware config menus.  As far as I know, all
> stand-alone motherboards have a CSM (Win 10 tablets often do not).
> 
> - System Management Mode is a little known feature of all Intel
> and AMD x86 processors since the 486 and the Am486 25 years ago.
> It allows the firmware to keep some control after booting the OS.
> The OS has no control over this.
> 
> - SMM is used (among other things) to capture USB keyboard and
> mouse events and turn them into simulated PS/2 events.  This is
> usually optional but default behaviour on motherboards.  In effect,
> this emulation appears to be a hardware feature.
> 
> - One other limitation of USB and not PS/2 is that there is a limit
> to how many keys can be pressed at once (n-key rollover) and
> sensed properly.  The limit is based on how many key events can be
> recorded in a single USB packet.  But the limit is something like
> 6.  Surely more than enough.
> 
> So: mouse emulation and BIOS emulation are behind the back of the
> OS. This means legacy OSes should have no trouble with these
> features.
> 
> I recommend using a USB keyboard and mouse.  Unless you are a crazy
> gamer. --- Talk Mailing List talk at gtalug.org 
> https://gtalug.org/mailman/listinfo/talk
> 

- -- 
Bob Jonkman <bjonkman at sobac.com>          Phone: +1-519-635-9413
SOBAC Microcomputer Services             http://sobac.com/sobac/
Software   ---   Office & Business Automation   ---   Consulting
GnuPG Fngrprnt:04F7 742B 8F54 C40A E115 26C2 B912 89B0 D2CC E5EA



-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2
Comment: Ensure confidentiality, authenticity, non-repudiability

iEYEARECAAYFAlq8AMIACgkQuRKJsNLM5erSYQCgx0xa7BWK8puxukaSfEIeyowv
VioAoOVidXAuYha15uCokaVkZkINtbsA
=3L7N
-----END PGP SIGNATURE-----