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From: Bob I on 4 Jun 2010 09:01


Stefan Patric wrote:
> On Thu, 03 Jun 2010 07:39:24 -0500, Bob I wrote:
>
>
>>Stefan Patric wrote:
>>
>>
>>>On Wed, 02 Jun 2010 13:51:37 -0500, Bob I wrote:
>>>
>>>
>>>
>>>>128 GB on XP-64 but 32-bit has 4 GB of address space, not 3.
>>>
>>>
>>>Technically, yes. But only about 3.2 is available to the user. The
>>>balance is reserved exclusively for the System.
>>>
>>>
>>
>>The variable amount of unused RAM is entirely dependant on the
>>particular hardware installed on the particular computer. The OP stated
>>that 3 GB was the limit and that is incorrect. As to 3.2 GB, once again
>>that is NOT a limit, nor is it "reserved", it is used to comunicate with
>>installed hardware. Remove or reconfigure hardware and the value will
>>change. All you can say is that 3.2 GB is an approximate value for
>>common pc configurations.
>
>
> And that is why I said "about 3.2" meaning not exactly 3.2, but around
> 3.2 or approximately 3.2. Even on a system with the barest of hardware,
> I myself have never seen more than about 3.35 available. Although, I've
> read claims of 3.5.
>
> Also, what would you call RAM that is exclusively accessible ONLY by the
> system for its use, that is, users or their apps can't access it? To me,
> that is the very definition of "reserved."
>

I've seen anywhere from 2.7 to 3.7 available out of 4 GB. and it is the
memory addresses that are being used not the memory itself. Give it
up, you're clutching at straws.

From: Tim Slattery on 4 Jun 2010 09:26
Bob I <birelan(a)yahoo.com> wrote:

>128 GB on XP-64 but 32-bit has 4 GB of address space, not 3.

Yes, but that 4GB space is used to access video RAM, BIOS, and a few
other things besides system RAM.

--
Tim Slattery
Slattery_T(a)bls.gov
http://members.cox.net/slatteryt
From: Bob I on 4 Jun 2010 10:17
Yep, that dead horse has been tenderized

Tim Slattery wrote:
> Bob I <birelan(a)yahoo.com> wrote:
>
>
>>128 GB on XP-64 but 32-bit has 4 GB of address space, not 3.
>
>
> Yes, but that 4GB space is used to access video RAM, BIOS, and a few
> other things besides system RAM.
>

Yep, that dead horse has been tenderized

From: Stefan Patric on 4 Jun 2010 14:09
On Fri, 04 Jun 2010 08:01:38 -0500, Bob I wrote:

> Stefan Patric wrote:
>> On Thu, 03 Jun 2010 07:39:24 -0500, Bob I wrote:
>>
>>
>>>Stefan Patric wrote:
>>>
>>>
>>>>On Wed, 02 Jun 2010 13:51:37 -0500, Bob I wrote:
>>>>
>>>>
>>>>
>>>>>128 GB on XP-64 but 32-bit has 4 GB of address space, not 3.
>>>>
>>>>
>>>>Technically, yes. But only about 3.2 is available to the user. The
>>>>balance is reserved exclusively for the System.
>>>>
>>>>
>>>>
>>>The variable amount of unused RAM is entirely dependant on the
>>>particular hardware installed on the particular computer. The OP stated
>>>that 3 GB was the limit and that is incorrect. As to 3.2 GB, once again
>>>that is NOT a limit, nor is it "reserved", it is used to comunicate
>>>with installed hardware. Remove or reconfigure hardware and the value
>>>will change. All you can say is that 3.2 GB is an approximate value for
>>>common pc configurations.
>>
>>
>> And that is why I said "about 3.2" meaning not exactly 3.2, but around
>> 3.2 or approximately 3.2. Even on a system with the barest of
>> hardware, I myself have never seen more than about 3.35 available.
>> Although, I've read claims of 3.5.
>>
>> Also, what would you call RAM that is exclusively accessible ONLY by
>> the system for its use, that is, users or their apps can't access it?
>> To me, that is the very definition of "reserved."
>>
>>
> I've seen anywhere from 2.7 to 3.7 available out of 4 GB. and it is the
> memory addresses that are being used not the memory itself. Give it
> up, you're clutching at straws.

Based on Paul's explanation making a distinction between "reserved" and
"inaccessible," it seems the word "reserved" has special meaning to those
who's vocation are computers other than how it is general used.

Stef
From: Paul on 4 Jun 2010 20:32
Stefan Patric wrote:
> On Fri, 04 Jun 2010 08:01:38 -0500, Bob I wrote:
>
>> Stefan Patric wrote:
>>> On Thu, 03 Jun 2010 07:39:24 -0500, Bob I wrote:
>>>
>>>
>>>> Stefan Patric wrote:
>>>>
>>>>
>>>>> On Wed, 02 Jun 2010 13:51:37 -0500, Bob I wrote:
>>>>>
>>>>>
>>>>>
>>>>>> 128 GB on XP-64 but 32-bit has 4 GB of address space, not 3.
>>>>>
>>>>> Technically, yes. But only about 3.2 is available to the user. The
>>>>> balance is reserved exclusively for the System.
>>>>>
>>>>>
>>>>>
>>>> The variable amount of unused RAM is entirely dependant on the
>>>> particular hardware installed on the particular computer. The OP stated
>>>> that 3 GB was the limit and that is incorrect. As to 3.2 GB, once again
>>>> that is NOT a limit, nor is it "reserved", it is used to comunicate
>>>> with installed hardware. Remove or reconfigure hardware and the value
>>>> will change. All you can say is that 3.2 GB is an approximate value for
>>>> common pc configurations.
>>>
>>> And that is why I said "about 3.2" meaning not exactly 3.2, but around
>>> 3.2 or approximately 3.2. Even on a system with the barest of
>>> hardware, I myself have never seen more than about 3.35 available.
>>> Although, I've read claims of 3.5.
>>>
>>> Also, what would you call RAM that is exclusively accessible ONLY by
>>> the system for its use, that is, users or their apps can't access it?
>>> To me, that is the very definition of "reserved."
>>>
>>>
>> I've seen anywhere from 2.7 to 3.7 available out of 4 GB. and it is the
>> memory addresses that are being used not the memory itself. Give it
>> up, you're clutching at straws.
>
> Based on Paul's explanation making a distinction between "reserved" and
> "inaccessible," it seems the word "reserved" has special meaning to those
> who's vocation are computers other than how it is general used.
>
> Stef

It does. "Reserved" means the function is not documented. It may not
rule out absolutely, the ability to access the thing. You may still be
able to read or write a Reserved location.

"Inaccessible" is more absolute, in that any attempt to use the resource
will be repulsed by force (bus fault handler etc.). In this specific case,
the problem is, there is no architectural connection, between some 800MB
of memory locations, and the address bus on the processor. No 32 bit addresses
sent by the processor, can get to those memory locations.

If the processor is set up to use 36 bit addresses (i.e. PAE),
then those locations could be accessed. They'd no longer be
inaccessible, due to a decoding limitation.

Compare these two chip specifications.

Address 0x08 Reserved
Address 0x04 Master_Reset
Address 0x00 Device_ID

versus this one

Address 0x04 Master_Reset
Address 0x00 Device_ID

If I probe location 0x08 on the second chip, I get a bus fault ("Inaccessible").
If I probe location 0x08 on the first chip, I get data, but I don't
know what it does.

I may be able to write to location 0x08 on the first chip, but since
I don't know what the location does, the chip may go nuts as a result
of me playing around. Engineers at the motherboard companies, spend
part of their day, doing exactly that, to discover functions that
Intel does not document. In that context, Reserved means "we're not
telling you what this does" and it also means "we reserve the
right to change what this register does, in any new revision of
chip we release". The register may still happen to work, but
only a fool would depend on it for some function. Some BIOS are
written to access Reserved locations, at the peril of a new
chip revision failing to work properly as a result. It means if the
chip revision is changed, the motherboard design team has to
re-test their hardware design again, for collateral damage.
So fooling around with a Reserved resource, wastes engineering
resources.

Paul
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