Mixing DIMM and SIMM?

[Will]

Hello all
Please excuse the ignorance, I know just enough about building a system
to be dangerous...but, I've got an Asus txp4 motherboard that I'm trying
to upgrade. Board has 4 SIMM slots presently filled with 4 x 16 MB EDO
Ram.
Have 2 DIMM slots for 168-Pin SDRAM empty.
Can I mix DIMM's and SIMM's and simply fill the two empty DIMM slots to
increase RAM? Or am I just looking for trouble?
Would prefer to save $$$ by not having to go all EDO or throwing out
existing chips.

Thanks
Will

[Paleo Pete]

Occasionally you'll fins a motherboard that will allow SIMM and DIMM to be mixed, but I've never seen one, just heard of them. In most cases it's a bad idea, use one or the other.

If you decide to go with DIMM, don't throw the SIMMs out, send 'em to me! (just kidding)

I would think rather than get more SIMM memory, if you have to buy more at all go with DIMM, check the motherboard manual, it may support SDRAM too, which would be a bit faster. If you go that route, you can go up to 128MB with one chip. The max with 72 pin SIMM is 64MB per chip, if you can find them, usually it's 32MB.

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[Will]

Thanks Paleo Pete

A visit to the Asus web site archives tells me that 3.3 v 168-Pin Dimm Module with SDRAM is the way to go, so I guess I'll pop in a pair of 64 MB for a total of 128. Pity about the SIMM's though.
This is all coming about as a result of me trying to install an HP9350i CD-Writer in the system and suffering horrible buffer enderrun errors.
I figure that more RAM might help...after that it might be a hard drive upgrade or processor. Has a Pentium 200 MMX now with a 2 Gig drive.
I refuse ( (ok...as a last resort) to give up and go with a whole new box.

Thanks again

Will

[Will]

Okay, Will here again.

Installed two 64MB 168-Pin DIMM modules today. (AZEN 64 MB PC100)
Machine booted right up and memory check came in okay,.....and then Windows 98 went kablooie with all kinds of fatal error messages and machine froze.
Could not get Windows to start even in safe mode.
Out came the DIMM's and in with the old SIMM's to get things going again.
Is there a change I shuld be making to the BIOS or Setup files?
Do I have to re-install Windows 98 to get it to recognize the new RAM?
Are the PC100 modules too fast for this old dinowaur of a motherboard?

Will

[Paleo Pete]

May be the wrong type. Check the PC Guide's System Memory section and the section on BIOS Settings If the memory is the correct type, you might have to change a BIOS setting or two.

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[Will]

Paleo Pete
You are indeed the Grand Master Geek.
I bow to your excellence.
....oh..and by the way, thanks for the help.

I now have 128MB of 168 Pin Dimm and my original 64 MB Simm's happily co-existing (so far anyway) for a total of 196 MB of Ram.
This thing flies now.
Your PC Guide help file did indeed help, although I have to admit I'm not sure which one of the suggestions did it.
Things seemed to fall into place once I un-installed my virus checker, set BIOS back to default, re-installed all the memory and let her fly.

Thanks again

Will

[Paleo Pete]

Thanks for the compliments, and I hope it keeps working. In many cases boards won't work if the two types are mixed, but sometimes they will. Looks like yours will...

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[herbert]

Consult your motherboard manual before mixing SIMMs and DIMMs.

Here is a quote from the ASUS TX97-E motherboard manual:

"WARNING: Do not install both SIMMs and DIMMs at the same time or else you will burn your memory. Mixing SIMMs and DIMMs require 5.0 Volt (signal level) tolerant memory chips which are not currently available."

Nasty!

[Will]

Hi Herbert

Ouch, that does sound nasty. I'm assuming that if the memory modules were going to burn out because of voltage incompatibility that they would do so pretty much the first time you boot up? I've been running both the DIMM's and SIMM's in my TXP4 now for 4 or 5 days with the system running at least 5 or 6 hours a day. Does your manual mention anything?
The only negative side effect I have noticed so far is that a few of my programs (web browser for one) had a slight stability problem, but that seems to be cured after re-installing.

[herbert]

Hello Will

The manual for one of my machines shows a configuration table for using SIMMs and DIMMs together and I have 2x32MB SIMMs and a 32MB DIMM installed in it. No problem.

I came across the warning while researching another problem and thought it a good idea to post it here in case others automatically assume that mixing SIMMs and DIMMs is safe.