Maximum memory with SLI? - Tilted Forum Project Discussion Community

Dilbert1234567 · 06-03-2006, 05:02 PM

So I just got my second 6800 ultra installed last night, and I noticed that the maximum memory dropped to 2 gigs, instead of the 2.5 gigs I have. Has any one read anything or seen anything about a maximum memory with SLI? BIOS says 2.5 gigs, 2.0 gigs available.

MB Asus A8n-SLI
CPU AMD 64 Winchester 3500+
Memory, 2 sticks of 1 gig, 2 sticks of 256

Dilbert1234567 · 06-05-2006, 04:58 PM

Well I figured it out my self. so you guys know, I’m running xp32, as a 32 bit OS, it can only address 4 gigs of addresses, the card pushed me over the 4 gigs so the memory is not addressed. All I need to do is switch to xp 64 and I’ll be good.

256MB memory space is reserved for I/O APIC and BIOS EPROM
256MB is reserved for configuration space memory mapping access for PCI Express
256MB is reserved for PCI Bridge Device, IDE Controller, USB Devices, On-board Audio
600MB for the 2 video cards
2560MB for the main memory

Gives me a total of 3928 megabytes, not including the RAID array, and several other devices, which makes up the remaining 512MB I am missing.

xepherys · 06-07-2006, 09:07 AM

Errr... video memory doesn't count as OS addressable memory I don't believe (in fact I'd say I know for sure, but I'm only about 99.9% positive on that). Also, how did the 6800 put you over? They have 1GB of RAM each? What 6800's do you have? Also, reserved memory space is carved out of the 2.5GB of system memory you have, so that doesn't count either.

Perhaps it's a driver issue?

Dilbert1234567 · 06-07-2006, 03:05 PM

Everything inside the computer has to be addressed, and 32 bit is all you get to do it, that is 4 gigs, look inside of device manager and sort by connection type and look at all the memory addresses you are using. You will find every device has its own set of addresses it takes up. If it’s not addressed it can’t be used.

I just went through the device manager, and after adding up all the addresses:

PCI bus: 1.98 GB
System Board: 2.00 GB

For a total of 3.98 GB

So in a since I have 20 Megs of memory that is missing, everything else is accounted for. Holy cow my PCI Bus has 2 GB of addresses allocated to it, wow.

I’m going to try turning off some of the onboard devices I don’t use, parallel, LPT, fire wire, etc.

xepherys · 06-07-2006, 05:55 PM

Erm, no, again I don't think this is correct. Those "reserved" memory spots you see in device manager are slices of system RAM that are set aside for use by those hardware systems.

"PCI Bridge Device, IDE Controller, USB Devices, On-board Audio"

Aside from MAYBE your audio card, none of those have additional RAM ICs attached to them to ADD memory top the system, they just subtract available memory from system RAM.

If you look at the MS paper here, please note "Windows XP Professional x64 Edition supports up to 128 GB of physical RAM and 16 TB of virtual memory. By comparison, 32-bit Windows is capable of supporting up to 4 GB of system memory, with up to 2 GB of dedicated memory per process."

System memory does NOT include memory on other devices (such as video cards, RAID controllers, SCSI cards, audio cards, etc.).

My comments on video memory, however, fall apart when you use onboard video with Shared Memory Architecture (SMA) which is rare these days. The issue ius partially due to the fact that the system splits memory into 2GB app and 2GB kernel. PCI devices ALWAYS steal a little memory. Another card will steal memory no matter what it is or if it has onboard memory or not.

catback · 06-07-2006, 06:47 PM

Quote:

Originally Posted by xepherys

Erm, no, again I don't think this is correct. Those "reserved" memory spots you see in device manager are slices of system RAM that are set aside for use by those hardware systems.

"PCI Bridge Device, IDE Controller, USB Devices, On-board Audio"

Aside from MAYBE your audio card, none of those have additional RAM ICs attached to them to ADD memory top the system, they just subtract available memory from system RAM.

If you look at the MS paper here, please note "Windows XP Professional x64 Edition supports up to 128 GB of physical RAM and 16 TB of virtual memory. By comparison, 32-bit Windows is capable of supporting up to 4 GB of system memory, with up to 2 GB of dedicated memory per process."

System memory does NOT include memory on other devices (such as video cards, RAID controllers, SCSI cards, audio cards, etc.).

My comments on video memory, however, fall apart when you use onboard video with Shared Memory Architecture (SMA) which is rare these days. The issue ius partially due to the fact that the system splits memory into 2GB app and 2GB kernel. PCI devices ALWAYS steal a little memory. Another card will steal memory no matter what it is or if it has onboard memory or not.

Everything in a computer is memory and is addressed, with 32-bit you only have 32-bits to work with which is 4GB...doesn't matter if it's a memory chip or a IC, to the computer it's just another memory location to work with. As far as the subtracting from the system memory, it doesn't happen that way...system memory has it's own address's just like all the other devices in the computer, what can happen is system memory can be reserved for particular use. The area where it can get cloudy is with hard drives, cd/dvd drives, and the like...simple explanation is the controller on the hard drive or cd/dvd drive has an address the computer can talk to and it then tells the controller what to do (get this or put this), the computer doesn't directly access the hard drive or cd/dvd.

Dilbert1234567 · 06-07-2006, 10:15 PM

Quote:

Originally Posted by xepherys

Erm, no, again I don't think this is correct. Those "reserved" memory spots you see in device manager are slices of system RAM that are set aside for use by those hardware systems.

"PCI Bridge Device, IDE Controller, USB Devices, On-board Audio"

Aside from MAYBE your audio card, none of those have additional RAM ICs attached to them to ADD memory top the system, they just subtract available memory from system RAM.

If you look at the MS paper here, please note "Windows XP Professional x64 Edition supports up to 128 GB of physical RAM and 16 TB of virtual memory. By comparison, 32-bit Windows is capable of supporting up to 4 GB of system memory, with up to 2 GB of dedicated memory per process."

System memory does NOT include memory on other devices (such as video cards, RAID controllers, SCSI cards, audio cards, etc.).

My comments on video memory, however, fall apart when you use onboard video with Shared Memory Architecture (SMA) which is rare these days. The issue ius partially due to the fact that the system splits memory into 2GB app and 2GB kernel. PCI devices ALWAYS steal a little memory. Another card will steal memory no matter what it is or if it has onboard memory or not.

well i'm sorry, but you are just wrong. please read this thread over, it goes through the problem.
http://64.233.167.104/search?q=cache...ient=firefox-a

here is someone else with the same problem, and again it is fixed when 64 bits of address space are availible
http://www.hardwareanalysis.com/content/topic/58925/

06-03-2006, 05:02 PM	#1 (permalink)
Dilbert1234567 Devils Cabana Boy Location: Central Coast CA	Maximum memory with SLI? So I just got my second 6800 ultra installed last night, and I noticed that the maximum memory dropped to 2 gigs, instead of the 2.5 gigs I have. Has any one read anything or seen anything about a maximum memory with SLI? BIOS says 2.5 gigs, 2.0 gigs available. MB Asus A8n-SLI CPU AMD 64 Winchester 3500+ Memory, 2 sticks of 1 gig, 2 sticks of 256 __________________ Donate Blood! "Love is not finding the perfect person, but learning to see an imperfect person perfectly." -Sam Keen

06-05-2006, 04:58 PM	#2 (permalink)
Dilbert1234567 Devils Cabana Boy Location: Central Coast CA	Well I figured it out my self. so you guys know, I’m running xp32, as a 32 bit OS, it can only address 4 gigs of addresses, the card pushed me over the 4 gigs so the memory is not addressed. All I need to do is switch to xp 64 and I’ll be good. 256MB memory space is reserved for I/O APIC and BIOS EPROM 256MB is reserved for configuration space memory mapping access for PCI Express 256MB is reserved for PCI Bridge Device, IDE Controller, USB Devices, On-board Audio 600MB for the 2 video cards 2560MB for the main memory Gives me a total of 3928 megabytes, not including the RAID array, and several other devices, which makes up the remaining 512MB I am missing. __________________ Donate Blood! "Love is not finding the perfect person, but learning to see an imperfect person perfectly." -Sam Keen

06-07-2006, 09:07 AM	#3 (permalink)
xepherys <3 TFP Location: 17TLH2445607250	Errr... video memory doesn't count as OS addressable memory I don't believe (in fact I'd say I know for sure, but I'm only about 99.9% positive on that). Also, how did the 6800 put you over? They have 1GB of RAM each? What 6800's do you have? Also, reserved memory space is carved out of the 2.5GB of system memory you have, so that doesn't count either. Perhaps it's a driver issue? Last edited by xepherys; 06-07-2006 at 09:12 AM.. Reason: Automerged Doublepost

06-07-2006, 03:05 PM	#4 (permalink)
Dilbert1234567 Devils Cabana Boy Location: Central Coast CA	Everything inside the computer has to be addressed, and 32 bit is all you get to do it, that is 4 gigs, look inside of device manager and sort by connection type and look at all the memory addresses you are using. You will find every device has its own set of addresses it takes up. If it’s not addressed it can’t be used. I just went through the device manager, and after adding up all the addresses: PCI bus: 1.98 GB System Board: 2.00 GB For a total of 3.98 GB So in a since I have 20 Megs of memory that is missing, everything else is accounted for. Holy cow my PCI Bus has 2 GB of addresses allocated to it, wow. I’m going to try turning off some of the onboard devices I don’t use, parallel, LPT, fire wire, etc. __________________ Donate Blood! "Love is not finding the perfect person, but learning to see an imperfect person perfectly." -Sam Keen

06-07-2006, 05:55 PM	#5 (permalink)
xepherys <3 TFP Location: 17TLH2445607250	Erm, no, again I don't think this is correct. Those "reserved" memory spots you see in device manager are slices of system RAM that are set aside for use by those hardware systems. "PCI Bridge Device, IDE Controller, USB Devices, On-board Audio" Aside from MAYBE your audio card, none of those have additional RAM ICs attached to them to ADD memory top the system, they just subtract available memory from system RAM. If you look at the MS paper here, please note "Windows XP Professional x64 Edition supports up to 128 GB of physical RAM and 16 TB of virtual memory. By comparison, 32-bit Windows is capable of supporting up to 4 GB of system memory, with up to 2 GB of dedicated memory per process." System memory does NOT include memory on other devices (such as video cards, RAID controllers, SCSI cards, audio cards, etc.). My comments on video memory, however, fall apart when you use onboard video with Shared Memory Architecture (SMA) which is rare these days. The issue ius partially due to the fact that the system splits memory into 2GB app and 2GB kernel. PCI devices ALWAYS steal a little memory. Another card will steal memory no matter what it is or if it has onboard memory or not. Last edited by xepherys; 06-07-2006 at 06:13 PM..