Can you limit the amount of usable RAM within a DIMM ?

I may run into a specific situation where I need to free more PCI address space otherwise taken my RAM. So is it possible to program a DIMM stick to make it smaller ? ... i.e. 1GB DDR2 DIMM to show as 768MB stick in BIOS for instance ?

thanks.

 

Yes, I believe there is a way in Windows to set it. Go to:

Start-->msconfig.exe-->Boot-->Advanced Options--->Maximum memory

After selecting the check box, type in the amount of memory you desire; you can also change the number of CPU cores that can be used, as well. You will have to reboot thereafter to see the effects.

 

not in Windows, I need to program that into the DIMM itself, I need it to show as smaller in BIOS.

 

Why not tell us what you are trying to accomplish?

Anyhow I've never seen anything like that, even in a desktop PC BIOS.

Laptop PC BIOS are generally much more limited, with the options that you can set in the BIOS.

 

Typhoon burner, maybe...


or buy 512mb sticks.

 

There isn't anything you are going to be able to do to increase available address space, at least not without buying smaller capacity RAM sticks.

 

Shouldn't reprogramming the SPD EEPROM/Flash to 1/2 the capacity work?
Of course just buying a smaller DIMM would be much easier.

 

programming it for 1/2 isn't worth the trouble since I can just buy 512MB DIMM. The thing is that I'm going to add external graphics card to my laptop via docking station and it works with up to 2.5GB RAM installed but doesnt work with 3GB RAM or more, thus the problem is somewhere within that 512MB above 2.5GB address region.

Now I run XP 32bit which reports ~2.9GB as usable RAM in Task Manager (I got 4GB RAM installer right now in both my T61 laptops), which is enough for 99% of the things I run, and I dont use page file. The most RAM in use I've seen is around 2.5GB when playing a heavy game. So if somehow I could use a "768MB DIMM" and a 2GB DIMM and that works out fine then I'll gain 256MB of RAM which will be worth having in this case, i.e. 2.75GB RAM total. XP itself can fit within 512MB RAM, and all the small utility programs at my start up are within 256MB, so that would leave a nice 2GB RAM window for a single program (game), which is the maximum standard memory window anyways.

I was hoping somebody with Typhoon burner experience to share thoughts ...

 

Are you absolutely sure it won't work with 3+2.5GB?

Most 32-bit addressing issues just ignore a portion over 4GB. ie: a 12GB system will show just over 3GB useable. The OS will cut things off for you when it has a choice of graphics memory and system memory.

What kind of docking station is this?

Is it more than just a pcie extension?

If you are only using the docking station for a pcie gpu, the OS won't know the difference anyway and treat it exactly as if you had inserted a graphics card on the pcie slot. I think you might be looking at the situation wrong.

 

thaiphoon burner can disable certain memory chips on stick... but I don't know how. It should be done if you know what memory chip is faulty and you don't want to RMA or throwing away whole stick.

Just use Windows XP x64 or Windows 7

 

again, this is not OS related, it's BIOS related. Once docked, the laptop can not boot when more than 2.5GB RAM and somewhat modern external GPU is installed. System beeps (1 long 2 short) for video card error when turned on. If the laptop is docked while working with more than 2.5GB RAM then the GPU is recognized but can not be used as it shows error 12 (can not allocate resources). Upon reboot same beeps pop up, and no boot at all.

disabling memory chips on the DIMM would work fine if it can be done. My two 1GB DIMMs here are with 16 chips each, so that is 64MB each.

it's the Lenovo Advanced Dock.

 

Using Thaiphoon you can change the SDRAM device parameters through the “Addressing and Capacity” dialog box. But it is not free program. And 1 license per computer. So make sure you really need it and make sure you will make it work for you as you want because it's author doesn't usually write How-To articles while most usual users like me do not use that features.
However you can try post your question and concerns about it here. It is possible that you get help there but you need to use Google translator for russian language.

 

Oh wow, ok. Just making sure you knew what you were up to, and clearly you do. I look forward to your solution!

 

Additional. You can download trial thaiphoon and play with that capacity feature. I could only either decrease the size up to 10% or so (changing # of bits from 8) or divide the capacity on 2 (1024 instead of 2048 etc.)

 

does the SPDTool do same thing as thaiphoon burner, but free of charge ?

because SPDTool gives me much more information on my currently installed 2GB modules compared to thaiphoon burner.

 

You can create a HEX image of thaiphoon, fix checksum and then type all those values in SPDTool. If it works on your laptop.
However it is not better than Thaiphoon. It is just free which is better.