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Unusual RAM issue with my IIsi.

Solvalou

Well-known member
Hmm, well this is odd. I got some non-parity RAM for my Macintosh IIsi and it appears to still be complaining with the 'chimes of death'. I've tried different sticks, different capacities, even paraty RAM just to be sure and all the same result. It boots just fine with none installed (well it would if my version of System 7 installed didn't use more then a MB of RAM to boot). Does anyone know why this would be happening? :-/

 

Byrd

Well-known member
I'm of the idea that RAM has to be installed in fours in a IIsi? At the very least, in pairs. This is why most IIsi machines come with 5MB (4 x 1 + 1MB onboard) or 17MB RAM (4 x 4 + 1MB onboard).

JB

 

trag

Well-known member
Must be sets of four identical SIMMs in the IIsi. The data bus on that machine is 32 bits wide and a 30 pin SIMM is only 8 bits wide, so it takes four of them to provide the necessary width.

If the original poster was using four identical SIMMs, then he should post back and let us know so we can move on to more complex possibilities.

 

Solvalou

Well-known member
I only tried with sets of 4 identical SIMM's and it gives the chimes of death. Tried pairs just in case with the same result.

 

trag

Well-known member
The first thing to try/hope is that you have a bit of dirt in your SIMM sockets. It could be as simple as a bad connection. First check that all the SIMM mounting posts (the little arms at the end that have the tab that goes in the hole in the SIMM) are in good condition and not broken off. If any are broken off, you'll need to compensate for that when installing the SIMMs. For example, one can often put something in between the SIMMs which will push the SIMM in the broken socket into place.

Then, get some card stock, e.g. 3" X 5" cards. Fold one in half. Moisten the folded edge with isopropyl alcohol (91% if you can get it, but 70% will do). Use isopropyl alcohol without any addititives (no colors or moisturizers).

Slide the folded edge of the card in and out of the SIMM sockets to gently rub the SIMM socket contacts with alcohol. Move on to a new card as needed.

Let dry, try again.

Another test is to try a different set of four SIMMs, but it sounds like you've tried several different sets.

If you have another Mac which uses 30 pin SIMMs, test your sets of memory in that Mac. Try to eliminate the variable of bad RAM, or incompatible RAM.

If all of the above fails, you either have a failed component on the logic board which is affecting the memory controller/memory sockets, or your power supply may be at the ragged edge of functioning and extra RAM increases the power draw just enough to cause failure.

If you have a voltmeter, measure the voltage on the 5V rail and determine if it is close to 5V or somewhere closer to 4.9V.

If you have the power supply from a IIcx, IIci, IIvi, IIvx, Quadra 700, Centris 650, Q650 or PM7100, you can pull the IIsi logic board out of the case and power it up with the power supply from any of the above. Of course, a spare IIsi power supply would work as well and you would not need to pull the logic board out of the case.

It is also possible that leaking electrolytic capacitors have deposited corrosive goo on your logic board which has eaten through some trace essential to memory expansion. The stuff is hard to see. It looks a bit like long dried cola spilled on the board.

 

Solvalou

Well-known member
Thanks trag for the comprehensive response. |)

That's a great idea about cleaning the contacts, I should have thought of it before! I'm certain I got some old floppy cleaning solution (about 93% icy I think) so that should do the job.

As for the caps, they look pretty nice at close inspection but I guess one never can tell. I have a friend of mine who re-capped my SE/30 and Amiga 1200 recently so if it is that issue then it shouldnt be a problem to fix later on.

I have noticed that it has no ROM SIMM installed. I actually have a spare at my friends (funny enough the one I just mentioned), i'm thinking that could be the possible cause for the chimes when any RAM is installed. Though in my experience from Mac's of old they usually they don't boot at all without a ROM SIMM, RAM or no RAM.

I have tested the 30 pin SIMM's and they appear working and fine in my LCII so that's something emiminated atleast.

Also I got a IIci spare so il try that if all else fails. :)

 

trag

Well-known member
I have noticed that it has no ROM SIMM installed. I actually have a spare at my friends (funny enough the one I just mentioned), i'm thinking that could be the possible cause for the chimes when any RAM is installed. Though in my experience from Mac's of old they usually they don't boot at all without a ROM SIMM, RAM or no RAM.
Correct. If it boots at all, then there is ROM installed. The huge majority of IIsi's had the ROM soldered to the logic board and never used a ROM SIMM in the socket.

 

Solvalou

Well-known member
I have noticed that it has no ROM SIMM installed. I actually have a spare at my friends (funny enough the one I just mentioned), i'm thinking that could be the possible cause for the chimes when any RAM is installed. Though in my experience from Mac's of old they usually they don't boot at all without a ROM SIMM, RAM or no RAM.
Correct. If it boots at all, then there is ROM installed. The huge majority of IIsi's had the ROM soldered to the logic board and never used a ROM SIMM in the socket.
Ah that would explain why it didn't boot with one installed. I had tried anotherr PSU and it is still the same issue. I guess all that's left is to clean the contacts... :-/
 
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