this is kind of interesting ...
---------- Forwarded message ---------- Date: Tue, 24 Sep 2002 10:02:49 -0700 From: Terry Lambert tlambert2@mindspring.com To: Danny Braniss danny@cs.huji.ac.il Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: 3.5GB memory limit?
Danny Braniss wrote:
the Addendum says: * AMD chipset architecture requieres memory above 3.5GB to be reserved for PCI devices.
We have a winner.
Q1: is this AMD specific, or also true for P3/P4?
It's chipset, not CPU specific. Your question is like asking if, because your Yugo (car) can't go faster than 100 KPH on one brand of gasoline, if it's a gasoline problem.
Q2: is there any way of accessing the 'lost' memory? ie some device driver?
No, not unless the chipset that imposes the limitation permits some form of bank selection.
-- Terry
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Not that the 3.5GB thing is a surprise, but what chipset were they talking about?
--Bob
On Tue, Sep 24, 2002 at 11:08:49AM -0600, Ronald G Minnich wrote:
this is kind of interesting ...
---------- Forwarded message ---------- Date: Tue, 24 Sep 2002 10:02:49 -0700 From: Terry Lambert tlambert2@mindspring.com To: Danny Braniss danny@cs.huji.ac.il Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: 3.5GB memory limit?
Danny Braniss wrote:
the Addendum says: * AMD chipset architecture requieres memory above 3.5GB to be reserved for PCI devices.We have a winner.
On Tue, 24 Sep 2002, Bob Drzyzgula wrote:
Not that the 3.5GB thing is a surprise, but what chipset were they talking about?
760 mpx I think.
ron
At 12:12 PM Tuesday 2002-09-24, Bob Drzyzgula wrote:
Not that the 3.5GB thing is a surprise, but what chipset were they talking about?
You'll run into something similar regardless of the chipset. 32-bit PCI cards need MMIO below 4GB, so a chipset must provide a memory hole for them. A "nice" chipset will allow you to remap the affected memory above 4GB, and a "nice" operating system will allow you to use that remapped memory.
Kimon
-- Kimon Berlin - HP/UX Workstation Lab - Firmware/Manageability https://ecardfile.com/id/kimonberlin If it's not on fire, it's a firmware problem.
Kimon Berlin kimon@hp.com writes:
At 12:12 PM Tuesday 2002-09-24, Bob Drzyzgula wrote:
Not that the 3.5GB thing is a surprise, but what chipset were they talking about?
You'll run into something similar regardless of the chipset. 32-bit PCI cards need MMIO below 4GB, so a chipset must provide a memory hole for them. A "nice" chipset will allow you to remap the affected memory above 4GB, and a "nice" operating system will allow you to use that remapped memory.
You can usually do a little better than 3.5GB if you only have a few pci cards or pci cards with a small mmio hole.
With a single quadrics card plugged into the E7500 I can still keep my hole down to 3.5GB. As far as I know the E7500 is either the only, or at the very least one of the very first chipsets to offer a remapping ability.
As far as accessing remapped memory. That is really dealing with memory about 4GB.
Eric
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Bob Drzyzgula -
Eric W Biederman -
Kimon Berlin -
Ronald G Minnich