On Fri, 17 Nov 2006 05:20:07 -0500, Trent <none (AT) dev (DOT) nul.pissoff>
wrote:

That is definitely false. I have pretty extensive experience on HP's
Business Desktop line, and every one of them will give you a beep code
(3 beeps) if there is no processor installed in the system. See page
A-13 from the following document:

http://h20000.www2.hp.com/bizsupport...Fc00368814.pdf


Dell has a similar code for their new Dimensions, where only light 3
of their diagnostics lights is on:

http://support.dell.com/support/edoc....htm#wp1064555


Note that these codes are NOT generated by any "8254 timer chip" as
such chips haven't existed on motherboards for 10+ years now. The
functionality of the 8254 timer chip has been incorporated into the
motherboard chipset, typically in the I/O controller or southbridge.
This is also where the "Keyboard MCU" resides and it's also where the
POST beeps (or blinking lights, or voice warnings on some new systems)
come from.

This is not some XT or AT system we're talking about here, things have
changed quite a bit in the past 25 years.
----------------------------
Tony Hill
hilla <underscore> 20 <at> yahoo <dot> ca

In comp.sys.ibm.pc.hardware.misc Franc Zabkar <fzabkar (AT) iinternode (DOT) on.net> wrote:
Yes, and actually most cannot, since the address lines and
handshaking lines are pure inputs. For the 8042 this is not true.
It has general purpose I/O and just pretends to be a
memory-mapped I/O device.

The 8042 can do a lot of things not in the normal operation description.
For example, it can control any signal deliverd to it.

Well. I think this discussion has reached the end of its usefulness.
See my other posting.

Look one posting further up....

Arno

In comp.sys.ibm.pc.hardware.misc Franc Zabkar <fzabkar (AT) iinternode (DOT) on.net> wrote:
P.S.: See the posting from Tony Hill for an example of a system that
does beep "no CPU". Also I agree with him, that the state of the art is
more important than the historic discussion.

Arno

In comp.sys.ibm.pc.hardware.misc Tony Hill <hilla_nospam_20 (AT) yahoo (DOT) com> wrote:


I agree to that. See my other posting were I describe that a
board with VIA chip from Epox does not sugnal anything if
the CPU is missing.

I guess today it just depends on the individual board. Also
anything done before the BIOS starts executing (which requires
the CPU to be present and working), is up to the board
manufacturer anyways.

Arno

On Sat, 18 Nov 2006 19:00:43 -0500, Tony Hill
<hilla_nospam_20 (AT) yahoo (DOT) com> put finger to keyboard and composed:

Hmmm, "Processor not installed" seems unambiguous to me. However,
AFAICS, the higher level diagnostic tests definitely require a
functioning x86 CPU and BIOS code.

That could still require a partially functioning CPU. Obviously all
the other tests require a functioning x86 CPU and BIOS code.

In fact test #1 in the BIOS POST routines of the original IBM AT was a
rudimentary CPU test. The program listing (yes, the Tech Ref Manual
lists the complete BIOS assembly code) states that test #1 writes 01
to the diagnostic port at 80h, and then tests the CPU's flags and
registers. If an error is detected, the test jumps to an error
handling routine consisting of a single instruction, HLT. There are no
beeps, no blinking lights. I suspect that the LEDs in your Dell
example are connected to port 80h, rather than to some special
hardware, in which case you could drive them using the Debug example
in my other post.

That's irrelevant. In fact chipsets that incorporated the
functionality of the 8254 timer were introduced in early 286
motherboards (eg VLSI Tech, Chips & Tech) way back in the early 90s.
But that doesn't change the fact that the speaker is driven from a
piece of silicon that emulates the functionality of the original
discrete 8254 chips. And that's what matters. If you are a Windows
user, any version of Windows, check you Device Manager I/O resource
list. You will find a speaker port at 61h and a system timer port at
40-43h, exactly where they have always been.

Agreed, but that does not prove that the keyboard MCU is doing the
talking. On the contrary it is obvious that certain POST routines
*must* be executed by the host CPU from BIOS code. For example, a ROM
checksum test, or a memory test, or a test for the presence of a
graphics adapter all require x86 intelligence.

Yes they have, but not the way you think. The fundamentals are still
there.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

On 19 Nov 2006 01:47:52 GMT, Arno Wagner <me (AT) privacy (DOT) net> put finger
to keyboard and composed:

Technobabble. The 8042 does not control the data bus. Period.

More technobabble. What an 8042 MCU can do in another application is
completely irrelevant. In a PC/AT the 8042 is just another I/O device.
It doesn't do DMA or bus mastering or anything exotic. It just does
what the host CPU tells it to do (via ports 60 and 64).

There is nothing in that post which is relevant to the present
discussion. Instead I suggest you examine pages 1,2,15, and 18 of your
own copy of the schematics and follow the signal path from the host
CPU, to the I/O decoder, to the timer, and then on to the speaker. We
don't need to speculate, the proof is in the schematics. If you have
difficulty understanding them, I'll be happy to explain, unless of
course you think I'm being arrogant.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

On 17 Nov 2006 23:54:02 GMT Arno Wagner <me (AT) privacy (DOT) net> wrote in Message
id: <4s70cqFubcoeU1 (AT) mid (DOT) individual.net>:

Suuuure...
*giggle*

Yep. I still have my IBM PC AT technical reference manual. Pg. 16 of 22 of
the schematics. Looks like that pesky old 8254 needs programming to me.
All those beep codes referenced by different BIOS manufacturers require a
processor that can run well enough to do code and data fetches from ROM.

I've been debugging to the component level on processor, memory, and I/O
boards since the 8080 days on Intel Multibus based systems, and you were
most likely still suckling at your dad's teat, you confused pinhead. Why
don't you quit while you're behind?

On 18 Nov 2006 22:35:31 GMT Arno Wagner <me (AT) privacy (DOT) net> wrote in Message
id: <4s9g5jFus4g6U1 (AT) mid (DOT) individual.net>:

I expect an apology is forthcoming?

On Sat, 18 Nov 2006 19:00:43 -0500 Tony Hill <hilla_nospam_20 (AT) yahoo (DOT) com>
wrote in Message id: <0b5vl2ddh90fa7ba8gtd6kcp280e7gsksh (AT) 4ax (DOT) com>:

I'd be curious to see a schematic of this motherboard, most likely it's a
simple watch dog timer which is triggered after a certain period of bus
inactivity. These are not the beep codes as referenced by the BIOS
manufacturers.
In any case, the OP in this thread's system is not an HP desktop it is a
homebuilt, and will not output POST beep codes if no CPU is present.

Irrelevant to the discussion, as there are no "beep codes" for a missing
CPU chip. Additionally, that LED code is probably generated by default at
power up. You could pry the chipset off the board with a big old
screwdriver, AND have a fully functioning CPU and get the same result.

[rolls eyes]

In other words, it is generated from an 8254. Whether or not it's buried
deep within the chipset matters not. There is still a device which behaves
and acts exactly like an 8254 - three programmable timers with numerous
modes of operation, and each MUST be programmed by the CPU before it will
do anything at all.

I've yet to see a design where the keyboard controller can write data to
the speaker.

Yet still there is a 100% software compatible 8254 device deep within. I
never stated there was a discrete 24 pin DIP device for the function.

From the 82801DB technical reference .pdf dated May 2003:

"The ICH4 contains three counters which have fixed uses. All registers and
functions associated with the 8254 timers are in the core well. The 8254
unit is clocked by a 14.31818 MHz clock."


You sig delimiter is improperly constructed.

On Sat, 18 Nov 2006 19:00:43 -0500 Tony Hill <hilla_nospam_20 (AT) yahoo (DOT) com>
wrote in Message id: <k81vl21mqpjk9601sb7kjhnd8h6tsuheqo (AT) 4ax (DOT) com>:

Funny, I don't have a single motherboard in-house that will do beep codes
if no CPU is present. These range from old socket 7 PICMG to modern i945
based core 2 ATX systems. From VIA mini ITX C3 and C7 to Pentium M 5.25"
embedded boards.

Not a Single Fucking One.

Also from the 82801DB reference manual:

"Speaker: The SPKR signal is the output of counter 2 and is internally
“ANDed” with Port 61h bit 1 to provide Speaker Data Enable. This signal
drives an external speaker driver device, which in turn drives the system
speaker. Upon PCIRST#, its output state is 0. NOTE: SPKR is sampled at the
rising edge of PWROK as a functional strap. See Section 2.20.1 for more
details."

Looking an old dual Pentium 2 reference design schematic from Intel
http://www.intel.com/design/chipsets...ex/gxdgsch.pdf
I see the 82371EB device that drives the speaker through a 2N3904
transistor. If you like, drag up the .pdf for the chipset and see for
yourself on pages 18 and 32.

Please elaborate.

If there is no CPU then the BIOS is completely irrelevant, as there will
be no code or data fetches from ROM.