For Computer/Electronic Engineer types -- Intel Data Sheet interpretation ?!?

[William Case]

Hi;

I have the 102 page Intel Data Sheet in front of me.  I am trying to
determine the High and Low voltage numbers for transistors on my
system.  

I am not trying to do anything mysterious or build a CPU in my garage.
I am just doing a small write up for myself that has an introductory
paragraph for a section on how DRAM memory works that says something
like "My machine's CPU and Memory transistors typically use XXX volts
when thrust High and XXX volts when driven Low."  I understand that
things can get more complex, but I am only trying to establish a sense
or feel of what is happening inside, not write a technical manual for
engineers.

All the various Vtt, Vcc, Vss, VID etc. are getting confusing.  I will
either have to spend a couple of days googling trying to interpret the
Data Sheet or take a short cut by asking here.

What designation or parameters should I be looking at for high and low
voltage (logical/binary 1 and logical/binary 0)?

I am using the Intel 318732.pdf {Core 2 Duo Processor Data Sheet}.

lshw says I have a:
product: Intel(R) Core(TM)2 Duo CPU     E7400  @ 2.80GHz
vendor: Intel Corp.
bus info: cpu@0
version: Intel(R) Core(TM)2 Duo CPU
slot: Socket 775
size: 1600MHz
capacity: 4GHz
width: 64 bits
clock: 266MHz

--
Regards Bill
Fedora 11, Gnome 2.26.3
Evo.2.26.3, Emacs 23.1.1

--
fedora-list mailing list
fedora-list@...
To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list
Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines

[David-712]

On Wed, Nov 4, 2009 at 4:34 AM, William Case <billlinux@...> wrote:

> Hi;
>
> I have the 102 page Intel Data Sheet in front of me.  I am trying to
> determine the High and Low voltage numbers for transistors on my
> system.
>
> I am not trying to do anything mysterious or build a CPU in my garage.
> I am just doing a small write up for myself that has an introductory
> paragraph for a section on how DRAM memory works that says something
> like "My machine's CPU and Memory transistors typically use XXX volts
> when thrust High and XXX volts when driven Low."  I understand that
> things can get more complex, but I am only trying to establish a sense
> or feel of what is happening inside, not write a technical manual for
> engineers.
>
> All the various Vtt, Vcc, Vss, VID etc. are getting confusing.  I will
> either have to spend a couple of days googling trying to interpret the
> Data Sheet or take a short cut by asking here.
>
> What designation or parameters should I be looking at for high and low
> voltage (logical/binary 1 and logical/binary 0)?
>
> I am using the Intel 318732.pdf {Core 2 Duo Processor Data Sheet}.

Somewhat off topic for this list ..
       
I have no expertise in this but out of curiousity I had a look at the
datasheet. My conclusions are below.
No doubt there will be others here with greater expertise who are
welcome to correct any errors.

Reference: http://download.intel.com/design/processor/datashts/318732.pdf

The intent of the datasheet is to describes its interfaces, not its
internal operation.

1) Table 2: the processor outputs a byte that controls the regulator
to provide it a supply voltage VCC in the range 0.5 to 1.6 V.

2) Table 4 Note 7: VTT is the databus (frontside bus FSB) fixed
reference voltage. It does not vary.

3) Table 3: VTT absmax = 1.45V

4) Table 4: VTT typical = 1.2V

5) Section 2.7: The databus uses GTL+. The "0 or 1" reference
threshold for input voltages is GTLREF which is derived from VTT by a
simple resistive divider.

6) Table 15: With resistors 57.6 and 100 ohm: GTLREF=VTT*100/(57.6+100)=0.76V

7) So for the databus:
Table 11: (approx) 0 < VIL < GTLREF   (VIL = voltage detected as 0 =
below 0.76V)
Table 11: (approx) GTLREF < VIH < VTT (VIH = voltage detected as 1 =
above 0.76V)
Table 11: (approx) VOH = VTT          (VOH = voltage output for 1 = 1.2V)
I could not see any VOL (voltage output for 0) for the FSB in this datasheet.

8) Table 12 and Table 13 specify open-drain and cmos interfaces which
use different voltages.

Background docs:
http://en.wikipedia.org/wiki/Gunning_Transceiver_Logic
http://focus.ti.com/lit/an/scea003a/scea003a.pdf (mentions VOL < 0.4V for GTL+)

Hope this is useful.
David

--
fedora-list mailing list
fedora-list@...
To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list
Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines

[William Case]

Thanks David;

> Somewhat off topic for this list ..

Yes I agree somewhat, but a couple of years ago I asked if this kind of
question was acceptable on the Fedora users list.  From time to time, I
have had questions that touch on the physical layer of my computer.  I
have no interest in becoming an Engineer.  If I ask on more technical
sites (I have tried) I either get answers that are so technical, they
are no answers at all -- for my purposes, or, people get aggravated at
such basic questions and feel that I am wasting their time.

On the other hand, on the Fedora list there are some people who like to
take a shot (like you just did) but can keep the answers at my level.
Some people have indicated the same interest or a passing curiosity,
that I have on how these things work.

I try to indicate in the Heading the type of question I am asking so
that those who want to skip the question can.

>
> I have no expertise in this but out of curiousity I had a look at the
> datasheet. My conclusions are below.
> No doubt there will be others here with greater expertise who are
> welcome to correct any errors.
>
> Reference: http://download.intel.com/design/processor/datashts/318732.pdf
>
> The intent of the datasheet is to describes its interfaces, not its
> internal operation.
>
> 1) Table 2: the processor outputs a byte that controls the regulator
> to provide it a supply voltage VCC in the range 0.5 to 1.6 V.
>
> 2) Table 4 Note 7: VTT is the databus (frontside bus FSB) fixed
> reference voltage. It does not vary.
>
> 3) Table 3: VTT absmax = 1.45V
>
> 4) Table 4: VTT typical = 1.2V
>
> 5) Section 2.7: The databus uses GTL+. The "0 or 1" reference
> threshold for input voltages is GTLREF which is derived from VTT by a
> simple resistive divider.
>
> 6) Table 15: With resistors 57.6 and 100 ohm: GTLREF=VTT*100/(57.6+100)=0.76V
>
> 7) So for the databus:
> Table 11: (approx) 0 < VIL < GTLREF   (VIL = voltage detected as 0 =
> below 0.76V)
> Table 11: (approx) GTLREF < VIH < VTT (VIH = voltage detected as 1 =
> above 0.76V)
> Table 11: (approx) VOH = VTT          (VOH = voltage output for 1 = 1.2V)
> I could not see any VOL (voltage output for 0) for the FSB in this datasheet.
>
> 8) Table 12 and Table 13 specify open-drain and cmos interfaces which
> use different voltages.
>
> Background docs:
> http://en.wikipedia.org/wiki/Gunning_Transceiver_Logic
> http://focus.ti.com/lit/an/scea003a/scea003a.pdf (mentions VOL < 0.4V for GTL+)
>
> Hope this is useful.

Yes, it was very useful.  It gave me the Gunning_Transceiver_Logic as
the appropriate search criteria for what I wanted to know.  This site
seems to cover it:
 
http://encyclopedia2.thefreedictionary.com/Gunning+Transceiver+Logic

"Gunning Transceiver Logic - (GTL) A standard for electrical signals in
CMOS circuits used to provide higher data transfer speeds with smaller
voltage swings The GTL signal swings between 0.4 volts and 1.2 volts
with a reference voltage of about 0.8 volts. Only a small deviation of
0.4 volts (or thereabouts) from the reference voltage is required to
switch between on and off states. Therefore, a GTL signal is said to be
a low voltage swing logic signal.

Gunning Transceiver Logic has several advantages. The resistive
termination of a GTL signal provides a clean signalling environment
Moreover, the low terminating voltage of 1.2 volts results in reduced
voltage drops across the resistive elements. GTL has low power
dissipation and can operate at high frequency and causes less
electromagnetic interference (EMI)."

I am going to make the assumption that the voltages used on the FSB
would be the same as are used by transistors inside the CPU and DRAM.

Thanks again !!

--
Regards Bill
Fedora 11, Gnome 2.26.3
Evo.2.26.3, Emacs 23.1.1

--
fedora-list mailing list
fedora-list@...
To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list
Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines