I haven’t written about my Mac ROM hacking lately, so this post will double as an update to my ROM hacking endeavors and a review of Seeed Studio‘s awesome Fusion PCB service.

After going through all the hoopla to desolder the DIP chips on my Mac IIci and socket them, I finally got frustrated. The main annoyance is that the DIP ROMs are all the way underneath the hard drive and floppy drive carrier. It was forcing me to basically rip everything out of the IIci in order to access the DIP sockets. I also had been in contact with the folks on the 68k Mac Liberation Army forums, and they had a lot of useful information, including the tidbit that many of the Mac II series machines (and the SE/30) have a SIMM socket that you can put a ROM SIMM into. My IIci also has this socket, and it’s easily accessible without removing anything from the case. So, I decided to make my own! Thanks to a lot of advice from fellow forum members, I was able to lay out a SIMM printed circuit board to have manufactured.

I ran into a problem: the SIMM needs to be about 0.047″ thick in order to physically fit in the socket. Most of the inexpensive circuit board prototyping manufacturers make boards that are 0.063″ thick. Luckily, bigmessowires from the 68k Mac Liberation Forums was able to recommend a PCB manufacturer that could make the boards in the thickness I needed: Seeed Studio Fusion PCB. He had used them in the past with good results, so I went for it.

Seeed Studio has amazing pricing. My board was about 3.85″ by 1.1″. That fits within a 10 cm by 5 cm rectangle. As of this writing, they can manufacture ten 2-layer boards of that size for a total of $24.90 plus shipping. That includes solder mask and silkscreen on both sides. It’s an incredible price! They also offer many thickness options, including 1.2 mm, which works out to 0.047″. I asked for red solder mask instead of the standard green, which added an additional $10 to the price. They have extremely good trace width/spacing requirements: 6 mil (0.006″) trace width and 6 mil spacing. I went ahead and made my minimum trace width and spacing 8 mils, just to be safe.

After you place your order online, you e-mail them a zip file containing the Gerber files for your PCB. If there are any problems, they will let you know — otherwise, you just have to wait for the boards to be manufactured and shipped.

Shipping was only $3.52 for registered air mail to the United States from Hong Kong. They had other options, too, but this was the least expensive one. They take PayPal as a payment option, and I can’t remember the other options they offered. I placed my order on the night of Monday, September 5, they shipped my board on Tuesday, September 13, and the package arrived on Friday, September 23.

I’m sure you’re wondering: how did the boards turn out? Well, they turned out just fine! As you can see, they were able to manufacture a board with an irregular shape:

You may see some numbers on the silkscreen. Seeed Studio’s directions tell you to add your order number to the silkscreen somewhere, so I did that on the bottom. They also added a few other numbers onto the top silkscreen. Not a big deal at all, especially for the price!

Electrically, the SIMM tested fine. All the traces were perfect. Seeed Studio will electrically test 5 of your boards for free, and you can pay to have the other 5 tested, too.

Oh, did I mention that they actually sent me 12 boards instead of 10? How cool is that?

I would highly recommend them if you are looking for budget PCB fabrication. They only do 1 or 2 layer boards, so you can’t do anything overly fancy with 4 or more layers, but 2 layers is plenty for all kinds of fun stuff you can make, such as this SIMM.

By the way, my SIMM ended up working perfectly, and it expanded my IIci’s ROM capacity to 2 MB (the original ROM is only 512 KB). I naturally tested the rest of the capacity by filling the remaining 1.5 MB with the Super Mario Bros music and turning it into the longest Mac startup chime ever:

If you’re curious what the assembled board looks like, I show it off briefly in the video.

So anyway, all in all, I had a very positive experience with Seeed Studio’s Fusion PCB service! I was shocked when I saw the pricing, and I am very happy with the boards I got back. Thanks, Seeed Studio!



  1. I can agree these guys are awesome. Total support!

  2. […] for fun, check out Doug's post where he changed his Macintosh IIci start-up tune to the Super Mario theme. If you do want to code ROM SIMMs, Doug has his ROM SIMM burner for sale […]

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