[TT030] what SIMMs for 4/16 MB TT-RAM expansion?

[Jacques]

Hi,

I recently bought a standard 4/16 MB TT-RAM board manufactured by ATARI on ebay.

 

According to this: http://www.geocities.ws/SiliconValley/Peaks/6320/ard/help/ttram01.htm

 

"TT RAM chips must be 30 pin 1Mb or 4Mb x 8 non-parity nybble mode SIMMs.

The 8 means 8 chips on each memory card, NOT 9 or 3 they will not work."

 

I set up the expansion correctly for 16 MB and have 4 x 4 MB SIMMs (but 3 chips on each).

But while the first TOS test indicates 16 MB of TT-RAM is detected and fine, later when using machine can I randomly get 2, 4 or even more bombs with TT-RAM attached. I've also run a test-program for TT-RAM (attached by someone on this forum) and it screams (in German! ) with thousands of errors...

 

Is the RAM organization on SIMMs to be blamed (3 chips on each, not 8 )?

Edited December 20, 2013 by Jacques

[qq1975b]

I do not know why 9 chips modules wouldn't work...9th is the parity chip and if the computer doesn't use parity it is useless and it is like an 8 chip module. I do not know about 3 chips modules (they're like 9 chip module)...Do you have 1MB 30 pin simms to test it with?

[dsmall]

It's been awhile since I've seen a TT, but I'll try to help.

 

 

"I set up the expansion correctly for 16 MB and have 4 x 4 MB SIMMs (but 3 chips on each).

But while the first TOS test indicates 16 MB of TT-RAM is detected and fine, later when using machine can I randomly get 2, 4 or even more bombs with TT-RAM attached. I've also run a test-program for TT-RAM (attached by someone on this forum) and it screams (in German! ) with thousands of errors..."

This kinda sounds like something which is failing from heat. (And where did you find nybble RAMs these days? :-)

If it were me, here's how I'd try to find the problem:

Take your TT apart to where you can get the TT RAM card.

Take the TT RAM card and put it in your refrigerator (not your freezer).

Once it's well cooled down, put it back in your TT.

Does it run pretty well? It probably will if this is a thermal (heat) intermittent.

Now let it warm up. A memory tester whacks away at the RAM chips and heats them up really well.

(I recently found out that the MemTest 86 in PC's can heat up RAMs to where they do fail.)

If it starts failing in a few minutes, you know there's a thermal problem.

So keep the TT RAM in the memory tester, take a can of compressed air, turn it upside down, and spray the chips one at a time on the TT RAM card

with the cool-it-down stuff from the air can. That'll take them far below 0 degrees very fast. (It doesn't take much.)

When the errors go away, you've found the chip that's heat-touchy.

You can also use a hair dryer to heat up the chips so you can also test.

What's usually a "thermal"? Well, connectors that get oxidation. (To clean off, use the eraser off a pencil exactly like the erasers you had in school.

Or a Big Indian Chief eraser. ) This is around 20 years old so it's not surprising.

You may need to pry up and put back down all the chips, which helps scrape through the oxidation.

Electrolytic capacitors can die of old age, look for a capacitor whose "lid" up top has been forced open.

If the heatup/cooldown cycle doesn't work, sometimes I've been known to look for suspicious solder connections and resolder them.

That's all the ideas I have. I do wish you luck!

-- thanks,

Dave

[Muzz73]

I have always understood that 9-chip SIMMs can always be used in place of 8-chip SIMMs, as the tag chip is ignored in non-parity systems. They probably tell you to only use 8-chip SIMMs in the manual, so that you would buy them from an Atari dealer back in the day and not opt for cheaper, PC memory. I know Apple used to tell everyone to only use 8-chip SIMMs in the Mac Plus and SE, but you could drop four 9-bit/9-chip SIMMs in there and everything worked fine. I used to repair those old Macs daily and saw it all the time.

[Nick Harlow]

I have a few of these boards in stock, complete with ram....if you want I will send you the ram type and specs?

[Zogging Hell]

Never trust the TT Ram check, it isn't very thorough. I had some simms which were bad and the TT ram check saw them as ok, took me quite a while of fiddling with the memory to work that out. I eventually stripped them out and replaced them and things were ok.

 

I would check the jumpers on the RAM board first though, they can make a big difference, you need to make sure they are set for 16mb

[frank.lukas]

Search for 8-Chip -60ns FPM Simm Modules it will be work fine ...

 

And play with the Burst Mode Jumper !

Edited March 24, 2014 by frank.lukas