IRQ's and Pnp OS's ...

[RJK]

Can I have your thinking on "PnP OS Yes/No" option setting in bios please.

I got to recently thinking about this because this evening I prodded the
power up button on my machine and got "thrown" into my bios settings because
they'd got lost, ( I will replace my button battery ...my, my, doesn't time
fly ...I only put this board in a year or so ago ...or was it two .. ?),
anyway,

I can remember, in the distant past, Mvp's advising to set it to 'yes' for
W98, and I can remember Mvp's advising W2k / XP users to set it to 'no'

I think my setting, (for XP Home ed.), is currently set to 'no'

I can remember issues in the long distant past, where one had to know which
expansion slot things were plugged into, (not going back so far as to when
one had to set IRQ and DMA jumpers on expansion cards !), to solve certain
problems. e.g. Creative cards liked having IRQ 5 assigned to the PCI slot
it was in, and some PCI modems liked to have IRQ 9 assigned to the PCI slot
it was in, ...some system boxes liked or required IRQ 10 for graphics.
....please, no lectures on IRQ sharing

Anyway, why did Mvp's advise the 'no' setting for NT type platforms, and is
there any reason not to set it to 'yes' for XP ?

You thoughts muchly appreciated.

regards, Richard

 

[Malke]

Can I have your thinking on "PnP OS Yes/No" option setting in bios
please.

Leave it set to "no". That way the operating system will handle this
function and not the BIOS.

Malke

 

[Lil' Dave]

The answer is "depends". If you have alot of hardware plugged into the PC,
and you can manipulate irq assignments to given PCI slots via the bios, and
you are familiar with each PCI card possible irq number assignments, set
"PNP OS" to "NO". This may give you an extra hardware irq to work with that
windows may waste in a plug n play environment.
Otherwise, set "PNP OS" to "YES". As an added note, you may have force
windows installation to set that environment by the proper setup switch.

 

[cquirke (MVP Win9x)]

Can I have your thinking on "PnP OS Yes/No" option setting in bios please.

Sure ;-)

I can remember, in the distant past, Mvp's advising to set it to 'yes' for
W98, and I can remember Mvp's advising W2k / XP users to set it to 'no'

I think my setting, (for XP Home ed.), is currently set to 'no'

After catching the background, you can prolly make up your own mind,
but I'll prolly expound and editorialize anyway

Non-boot PnP devices are supposed to stay inert until awakened by the
PnP manager, which assigns them resources. That PnP manager can be:
- BIOS PnP extension
- PnP OS
- a PnP add-on for a non-PnP OS (e.g. DOS mode)

Resource settings may be held in Non-Volatile RAM (NVRAM, in this case
also called ESCD). This is often flash ROM (like an EPROM) rather
than CMOS memory, and as such, may have a limited write life.

PnP was a brand-new MS OS facility that bound together the
"intelligence" of PCI and PCMCIA, and did what it could with
unintelligent interfaces such as ISA. It was pretty wobbly at first,
but got better as the years and OS versions rolled by, and as pre-PnP
interfaces such as ISA faded out of the box.


So now you can see you have two concerns:

1) Making sure all your OSs can use PnP devices
2) Preventing "ESCD wars" between squabbling PnP managers

On (1), remember that the DOS mode of your Win9x is not a PnP OS.
While it may inherit PnP "life" from Win9x GUI if your DOS mode .pif
is set to "use current...", it won't have anything after a reboot or
cold power up (F8 etc.) unless BIOS PnP does its thing.

So to keep DOS mode and other non-PnP OSs sweet, you may prefer to set
CMOS "PnP OS" = No, so that BIOS's PnP extension does its thing. Else
matters will be left up to the OS's PnP, and in the case of DOS, you'd
have to find and use some bulky PnP TSR, driver or utility.

On (2), often different PnP managers assign resources differently, or
store PnP info in ESCD NVRAM in a different format. Every time one
sees the changes of the other, it "corrects" them, potentially beating
the ESCD NVRAM to death.

To avoid this, you can either set CMOS "PnP OS" to Yes, thus disabling
BIOS PnP and leaving Win9x's PnP manager the undisputed champ; or you
can set Win95 (it's usually Win95 that needs this) Device Manager, PnP
BIOS, Properties, Settings to "[x] Disable NVRAM updates", or clicks
to that effect. IOW, you pick a winner and force the loser to STFU.

I can remember issues in the long distant past, where one had to know which
expansion slot things were plugged into, (not going back so far as to when
one had to set IRQ and DMA jumpers on expansion cards !), to solve certain
problems. e.g. Creative cards liked having IRQ 5 assigned to the PCI slot
it was in, and some PCI modems liked to have IRQ 9 assigned to the PCI slot
it was in, ...some system boxes liked or required IRQ 10 for graphics.
...please, no lectures on IRQ sharing

Yes, I remember those days... <gibber>.

PCI's a step backwards from ISA in that which slot you use, can be
significant. Even today, if you rebuild a PC and put PCI cards back
in the "wrong" slots, PnP is liable to re-detect everything, whine for
a driver disk, scramble previous resource allocations and chuck out
any settings you may have applied.

So I still locate "greedy" devices close to but one slot away from
AGP, and "slow" devices near the bottom of the case (noting the
lowermost slot may share IRQ with USB in the same way the topmost slot
may share IRQ with AGP). It helps if it's not Micro-ATX, of course.

Anyway, why did Mvp's advise the 'no' setting for NT type platforms,
and is there any reason not to set it to 'yes' for XP ?

I still like No. If I dual-boot XP and Linux, I'd rather have both
take theier cue from a common set of resource allocations made by BIOS
PnP than have them both hammering away at system-level ESCD data,
which is supposed to be outside OS scope anyway.

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Proverbs Unscrolled #31
"Mary and me on the beach.JPG .pif"

 

[RJK]

Thanx to all.

regards, Richard