T60 and T60p:
the T60 and T60p are based off of the intel socket M processors. no matter how much memory you install in these thinkpads, only 3GB will be addressable regardless of operating system used. this is a physical limitation and there is absolutely no workaround. if you have a T60/p then installing 4GB total system memory is a waste. save your money, stop at 3GB, and put the savings either in the bank or toward a T61/p if you want 4GB.
quoted from official lenovo documentation:
the key point to take away from this quote: the T60 and T60p are based off of the 945GM and 945PM chipsets and therefore fall under the 3GB physical limitation as stated above. even with 4GB total system memory and a capable OS, you still can't see or use more 3GB no matter what you do.Maximum memory capacity may require the replacement of standard component with largest supported component available. On ThinkPad systems with an Intel 945GM, 945PM, GM965, or PM965 chipset, even though it is possible to physically install 4GB of memory, the actual amount of memory addressable by an operating system will be limited to 3GB. This limitation does not exist with the Intel GM965 and PM965 with the 64-bit operating systems Windows XP Professional 64-bit and Windows Vista 64-bit Editions.
T61 and T61p:
the T61 and T61p are based off of the intel socket P processors. these systems are capable of using up to 4GB total system memory as long as you use the proper OS. below are the results from the four most popular microsoft OSes tested on my T61p.
operating systems tested:
- XP professional 32-bit SP2
- vista ultimate 32-bit
- server 2003 standard 32-bit SP2
- vista ultimate 64-bit
- thinkpad T61p (6459-CTO)
- BIOS 1.21 / 1.06 (7LET51WW)
- intel core 2 duo T7700 @ 2.4GHz
- nvidea quadro FX 570M @ 256MB
- crucial 2GB DDR2-667 SODIMMs (2 total; matched pair)
note: all pics below are under 50k per forum guidelines.
XP professional 32-bit SP2
result: 3.0 GB (3072 MB)
comments: XP pro SP2 now has PAE enabled by default. on my T61p it could only see 3 GB total. supposedly it can see as much as 3.5 GB using PAE so please keep in mind that my particular thinkpad has a lot of extras which could be eating up memory, ie; 256 MB GPU (512 MB total), WUSB card, atheros a/b/g/n card, bluetooth 2.0 EDR card, fingerprint reader, etc. -- all of which require addressable space. if my thinkpad had less VRAM then it might have another .25 GB free.
vista ultimate 32-bit
result: 3070 MB (3.0 GB)
comments: see XPP comments above. i tried running bcdedit /set pae ForceEnable to no avail. vista 32 is stuck with the 3.0~3.25 GB limitation just like XP.
server 2003 standard 32-bit SP2
result: 3.93 GB (4030 MB)
comments: this one surprised me. my initial thoughts were that 32-bit 2003 was going to act like any other 32-bit flavor of windows and limit everything to 3GB. instead, it was the first one which actually supported 36-bit addressing with memory hoisting to fully utilize all 4 GB of physical memory. thankfully lenovo engineered the T61/p to handle the magic 36-bit support combination necessary for this to happen (motherboard + BIOS + 36-bit capable operating system).
with that said, if you hate vista and are looking for a rock-solid 32-bit OS with 4 GB support then 2003 is your answer. install (most) of the lenovo drivers for XP/2000, then simply follow this handy guide to turn it into a workstation. the only thing i still can't get to work properly is the on-screen display for the volume keys. otherwise most everything else is (unofficially) supported.
vista ultimate 64-bit
result: 4030 MB (3.93 GB)
comments: no surprise here... 64-bit OSes are supposed to work as advertised with 4+ GB of physical memory. i would have been more surprised if vista x64 didn't work.
PAE is an interesting topic that pops up quite often when talking about memory limitations. while PAE might be a hack for 32-bit systems like XP pro and vista 32, it's not a hack for 36-bit capable systems like server 2003. also, we're now seeing "Physical Address Extension" enabled by default in XP/2003 service pack 2. obviously it's a viable enough "hack" that microsoft decided to save everyone the headache of adding PAE switches to their bootloaders.
my biggest surprise, again, was server 2003 standard 32-bit simply because most research and comments here on the thinkpads.com forum said that the most i'd see is 3.25~3.5 GB and not the 3.93 GB that i actually got. i guess that's why it's always best to ask for first-hand experience with pictures.
the results above should apply to all C2D socket P mobile processors in the T61/p and X61/s/tablet thinkpads. again, systems with integrated GPUs or less VRAM should see more than 3.0 GB total addressable memory. if i buy an X61 then i'll probably do this all over again just to see what happens with the 32-bit systems.
i hope my research is of help to others here. thanks and enjoy!