8GB in Vostro 1720?

Has anyone been able to run with 8GB RAM on a Vostro 1720 laptop?

Spec said 8GB, but I can only it working with 6GB [4GB + 2GB].

I had tried four different pairs [4GB + 4GB] of memory (Patriot (2), Dell, Crucial) - no luck.

I can see 8GB in BIOS. It can boot into Dell Diagnostics, but will either freeze or reboot itself within a couple of seconds after starting "Test Memory". It passes all other Dell system tests with no problems.

With Memtest86+ (v4.20), a few seconds after starting the test, it is frozen solid at TEST#4.

Also try to boot with Ubuntu Live CD (v10.10 64-bit) but it hanged after the initial splash screen.

I recalled some postings that other folks had similar issue with 8GB of RAM.

Any thoughts on whether this is a BIOS, hardware (memory controller?), a machine-specific problem or something else?

Can anyone shed some lights?

Appreciate any info and thanks in advance.

If someone had it working, which memory brand and part number did you use?

Reference links below:

CPU-Z is a free utility that can read the Manufacturer and Part number (click on SPD tab) - see link below

CPUID - System & hardware benchmark, monitoring, reporting
On the right hand side, under download latest release file (select zip, no installation)

Documentation Vostro 1720 Spec

Newegg.com - Patriot Signature 8GB (2 x 4GB) 200-Pin DDR2 SO-DIMM DDR2 800 (PC2 6400) Laptop Memory Model PSD28G800SK Memory I used

Newegg.com - Crucial 4GB 200-Pin DDR2 SO-DIMM DDR2 800 (PC2 6400) Laptop Memory Model CT51264AC800 I had also tried these Crucial

Amazon.com: Dell - Memory - 4 GB - SO DIMM 200-pin - DDR2 - 800 MHz / PC2-6400 - unbuffered - non-ECC: Electronics Also these Dell memory