Using more than 256 MB of memory on SB1250 in 32-bit mode
Is it possible to use more than 256 MB of system memory with the Broadcom SB1250 in 32-bit mode? The memory map I'm looking at shows me that the second 256 MB of memory is at physical address 0x80000000. I suspect that due to the 2G/2G split in the kernel, I can't use memory this high without moving to the 64-bit kernel.
Would someone confirm this for me?
Signature · 2 lines
Steve Madsen <[email protected]> Tadpole Computer, Inc. http://www.tadpole.com
Quoted 5 lines · Steve Madsen
Is it possible to use more than 256 MB of system memory with the Broadcom SB1250 in 32-bit mode? The memory map I'm looking at shows me that the second 256 MB of memory is at physical address
0x80000000. I suspect that due to the 2G/2G split in the kernel, I can't use memory this high without moving to the 64-bit kernel.
Steve Finney's answer was correct; I'd like to add a few details though.
The explanation you gave isn't exactly right. A 2GB/2GB split would normally support 2GB of low memory. We don't on MIPS due to the very inconvenient and unchangable mappings of KSEG0/KSEG1 - something that may have been sweet in '85 when the address map was designed but not today when 32-bit address spaces are beginning to be fairly tight.
Highmem works ok in 2.4 as long as you have a reasonably low ratio of highmem to lowmem. For typical loads that means going beyond 4:1 isn't sensible but the actual number may vary much based on exact system configuration or workload.
Ralf
Quoted 6 lines · Ralf Baechle
The explanation you gave isn't exactly right. A 2GB/2GB split would normally support 2GB of low memory. We don't on MIPS due to the very inconvenient and unchangable mappings of KSEG0/KSEG1 - something that may have been sweet in '85 when the address map was designed but not today when 32-bit address spaces are beginning to be fairly tight.
Quoted 7 lines
Highmem works ok in 2.4 as long as you have a reasonably low ratio of highmem to lowmem. For typical loads that means going beyond 4:1 isn't sensible but the actual number may vary much based on exact system configuration or workload.
Ralf
So what is a practical limit to total memory.
Daniel