Problem mixing PC100 and PC133

Hi everybody,

I recently bought an original Toshiba PC100 256 MB module (PA3069U-1M25) for my old Satellite 1805-S253 notebook - don't flame me, this old lady has a great sentimental value... - which already has a 256 MB PC133 SAMSUNG working fine for years.

The problem is that the computer refuses to start when both modules are installed. Both work fine in any of the two slots, but only when they are alone. Not together.

Does anybody know why?

The manual says I should use PC100 SODIMM SDRAM, but I know PC133 can also work at 100Mhz, and it should be ok to mix PC100 and PC133, right?

I could buy another Samsung PC133 (which is cheaper than the one I bought), but I'm afraid that this could also not work...

Cheers

 

I don't think that the motherboard of your notebook can support 133 Mhz RAM. I had a similar problem when i first upgraded the RAM on my desktop. I bought 133 MHz RAM, and it didn't work. I then bought some 100 Mhz RAm, and the system sprung into life. You may be having the same problem. It isn't always the case where memory can run at a lower frequency. Most do, but some simply don't. Its always better to go with the same frequency memory as you already have. Hope this helps.

 

The thing is I already had this PC133 Samsung module working trouble-free for years... and I tested it carefully before adding the Toshiba PC100. The PC133 definetely works.

Actually, both modules passed intensive tests. But alone. The problem is that they don't work together.

 

They should work together. If you swap the slots so that the PC133 stick that came with the notebook is in the slot that you are trying to put the PC100 stick in, and you leave the PC100 stick out, does it work?

 

Yes it works.

All possible arrangements with a single module works perfectly fine:

Slot 1 - PC133 / Slot 2 - empty
Slot 1 - empty / Slot 2 - PC133
Slot 1 - PC100 / Slot 2 - empty
Slot 1 - empty / Slot 2 - PC100

I performed several tests with all these configurations, so I conclude that not only both modules are fine, but also that both slots are ok.

When I try both modules together, however, the computer refuses to start:

Slot 1 - PC133 / Slot 2 - PC100
Slot 1 - PC100 / Slot 2 - PC133

The PC133 (Samsung) did not come with the notebook -- I bought it 2 or 3 years ago. The computer came with an original Toshiba 128 MB PC100 that I no longer have.

Unfortunately, I don't have other PC100 or PC133 to test other configurations. So I guess I have to buy another one (either a Samsung PC133 or a Toshiba PC100) so that I can try with two identical modules...

 

Run memtest on each stick individually:
www.memtest86.com

 

There's nothing wrong with your RAM. I suspect the higher frequency RAM is not downclocking when two of them are run in tandem. When you run the 133Mhz only, do you see what speed it is running at either upon startup or in the BIOS? If it runs at 133 Mhz then it could be that the module is so old that it does not support downclocking.

On the other hand, have you considered that perhaps your laptop simply cannot handle more than 256 MB? Maybe the two slots were meant for 128 MB strips, which sounds about right for older laptops.

 

I did it already... that's how I tested both modules separately. The tests run for hours without a single error...

 

No, it does run at 100Mhz (it's a 100Mhz FSB).

No, the notebook supports up to 2x256MB, for sure. It's in the manual. In any case, I know each slot can handle a single 256MB, so there's no reason why both shouldn't work together...

I guess it's some kind of incompatibility between the two different modules. Something that is not mentioned by the manufacturers...

The only solution I can think of is to buy another identical module. And that's what I'm doing at the moment: buying another Samsung PC133.

 

I found this at another forum:

http://reviews.ebay.com/Myth-Low-De...0001236178?ssPageName=BUYGD:CAT:-1:LISTINGS:3

Jump to breakpoint #3. I think it's a bit exagerated, but maybe it explains my problem...

Apparently I have a Toshiba PC100 which is low density and a Samsung PC133 which is high density (8 chips of 32Mx8).

Btw, I've ordered another Samsung PC133. Let's see if it works...

 

Having high and low density RAM mixed just won't work. I've been bitten by that before, but it's been so long I forgot As long as you have them the same, and the machine definitely works with the high density stick in, it should be fine.

 

Now I don't know if the problem was really because one was low density and the other high density. I have a feeling that both modules are high density as both have 8 chips...

Anyway, here's the full story in case anyone experiences the same problem... First, I returned the Toshiba module and bought another 256MB Samsung. Unfortunately, the module I bought was not exactly the same as the one I already had and, again, the computer refused to start when both were installed, although both worked fine when installed separetely.

I then returned the Samsung module and got two identical Toshiba PA3069U-1M25 256 MB PC100 modules on ebay, which are the ones originally shipped with the computer and... they work together! So now my old lady finally has 512 Mb of memory!

I don't really know what the problem was, but maybe old computers are just like that...

 

Just interested as I had a similar model, what's the spec of your Satellite 1800? I had a Sat 3000 which eventually succumbed to that intermittent psu fault and was sold for spares. Have you had any problems with that?

 

Satellite 1800-S253 PIII 850 MHz 14.1" TFT

what psu fault are you talking about?