Recent content by Builder68

Good Catch! Linking that schematic was worth it! I have to say, I find the way you use chat very enjoyable, like a kind of log of the thoughts, reflections, and decisions you make for the development of your project; it's much better than the stickers on the corkboard, isn't it? 😁

FYI, those ICs are also used in the 3MB RAM expansion board for the Macintosh Classic (Made by Garrett's Workshop) The design (Kicad) files are available at GitHub . That's interesting that this board is only 3 years old! It makes me think the designers faced a similar challenge to what you...

Hey, those ICs can be found on Aliexpress, Amazon or EBay! (By the way, I snagged a couple already to play around with your design as soon the arrived.). It looks like there is a large stock available (brand new) at several main suppliers.

You're absolutely right about the refresh rates! I completely missed that aspect. Regardless, your explanation was incredibly helpful and provided a much clearer, broader understanding of how RAM functions in the early Macs.

I'm also considering the KM44C4100 (4Mb x 4bit), in order to keep the CAS generation unmodified.

I got curious. Are there any reasons why the bigger 1MB x 16-bit CMOS FAST PAGE RAM ICs, like the ones in some Mac Classic/SE memory upgrades, wouldn't work in the early macs? The reason I ask is because those teeny 1Mbit x 4-bit chips you used in the prototype seem like a pain to find these...

Last night I also watched latest Adrian's video (Very well done, funny and entertaining, by the way, as are his videos usually). I couldn't agree more with you about the way of making the connections to the motherboard (which by the way would be a considerable improvement over the initial...

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Absolutely, moving to a PCB layout sounds like the way to go! On the topic of the ~CAS lines, pulling them high on the PCB can be very beneficial. It helps reduce noise. It also offers a slight power consumption reduction which is always a bonus. This is incredibly exciting! Your progress on...

I just want to confirm, did you cut the traces to pins 12 and 13 of the TSM chip?.

One way to simplify your prototype could be instead of using individual 1Mb DIPs, get a 3MB or 1MB w/ SIMM sockets RAM expansion board for the Macintosh Classic. One option is the 2024 820-0405-01 GW4406A, which you can find on eBay for $30 or less. This will reduce cable clutter...

I actually considered reverse engineering the Dove MacSnap RAM expansion board a while back. Luckily, I have some high-resolution pictures of the board that I'm attaching. Although the MacSnap is based on 1x256kb DRAM ICs, these pictures might be helpful for you to compare and verify your...

It sounds like you've put a lot of thought and effort into designing this memory upgrade board! While I'm no expert like you, here are some thoughts... The Mac 512K likely doesn't use dual-ported memory. Standard DRAM with data buffering on the logic board should work as planned. Choosing...

In the late 1980s, many tech enthusiasts and repair technicians commonly upgraded the onboard RAM of early Macintosh models. This process involved piggybacking additional DRAM chips onto the motherboard and adding chip registers to manage the expanded memory. While tempting for its performance...