Task: Replace Faulty RAM on Your Atari 8-Bit Computer Circuit Board
Needed: New DRAM and perhaps sockets, desoldering iron, hot air rework station, soldering iron and solder
Time: 30-60 minutes
Introduction
I recently received two nonworking Atari 800XLs that would boot straight to the RAM test. Both failed the RAM test almost completely with a grade of “F”. I discovered when I cracked them open that each was loaded with cheap Micron Technology (MT) DRAM 64Kx1 RAM chips that are notoriously unreliable. The photo below shows what these chips looks like after I removed them from the board.
Fortunately, one of the machines was socketed and I could do a quick swap with good RAM. The other I had to desolder and install new sockets (see two photos below).
Below are instructions for buying new RAM and links to posts about desoldering RAM chips and soldering in sockets if needed.
Instructions
Step one is to order new DRAM that is compatible with the Atari 8-bit computers. The first set of chips I ordered were refurbished Motorola 64Kx1 DRAM chips (150ns) from Jameco. I ordered 16 for the two machines at $2.59 each or about $20 per set of 8 (see first photo below). However, I discovered that 256Kx1 DRAM chips work just fine and are must cheaper and more common (the Atari ignores the additional memory beyond 64K). I purchased a second set of 25 DRAM chips from eBay (see below) for $13.23 which is about $0.50 per chip. Much cheaper at only $4 per Atari!
Step two is to remove the bad RAM chips from the board. Hopefully your Atari is socketed and you can pull them out with a chip lifter. If not, they will need to be desoldered. I have previously posted about desoldering and lifting chips out using a hot air gun. Once lifted, new sockets can be soldered in.
Step three is to insert the new DRAM chips in the sockets noting the notch orientation.
Step four is to run the built-in RAM test on the XL and XE machines and use something like a Super Salt cartridge for the Atari 400 and 800. Sys-Check II will pinpoint specific bad RAM chips.
Step five is to load some software to make sure everything is working correctly.
Comments
I recommend replacing all MT RAM you find in these machines as they will fail. I still need to crack open all my other machines to make sure there isn’t bad RAM waiting to blow.
Note that these DRAM chips have a read-write speed in nano seconds. The ones I used about were in the 100 to 150 ns range. I believe that chips with higher or lower ratings could be incompatible. I have read that chips up to 250 ns should be fine, but I have not tested this. The speed is indicated on the chip with a -10 for example on the NEC chips I purchased. Multiply this number x10 to get the ns rating.
This thread on Atari Age has a YouTube video on Micron Technology that made these bad chips by trying to undercut the competition.
At the time of this last note in Spring of 2025 the prices of RAM are going up due to demand and tariffs.