Intel 855PM chipset mystery/conspiracy

[Ron1]

Does anyone know how this is possibly:
My system has 855PM chipset with external marking:
SL752
This, according to
ftp://download.intel.com/design/chipsets/specupdt/25348802.pdf
would indicate B1 stepping. I have PC2700 memory installed and "working".
PCI register at offset 08 has value 03h, which indicates A3 stepping.
PCI register at offset E4 has value 4104a009, which indicates B stepping.
Benchmarks indicate I'm getting 2.0 GB/s reading and 2.0 GB/s writing,
which seems to indicate that the memory is running at 266 MHz, which my system vendor says it is.
There are 2 indication that the chipset is the B stepping
and 2 indications (1 being the bottom line performance) that it is the A stepping.
Is this some undocumented chipset from Intel?
I do not see anything in the Intel doc. that indicates this is possible!
Anyone have any info? comments?
Thanks.

 

[Guest]

Well, 7 years elapsed without answer.. I am now in the same shoes.

Upgraded from T40 mobo to T41 mobo for having 333MHz RAM support..
T40 mobo has SL6TJ, T41 mobo has SL752 chipset.

Found the same docs
http://www.intel.com/content/www/us/en/chipsets/855pm-chipset-mch-ddr-333-200-266-mhz-specification-update.html
saying that it is B1 stepping with DDR 333Mhz support

Also ebay specs says T41 supports PC2700 with 333Mhz.
http://reviews.ebay.com/IBM-ThinkPad-T40-T41-T42-T43-difference-guide?ugid=10000000004902772

CPUID and everest readouts both show that chipset is a3 stepping. Now I am preparing to buy PC2700 RAM but concerning about working on 266Mhz. Will update soon.