Game Doctor SF6 32M & 64M RAM card reverse engineering & reproduction

Websites that sell 32M and 64M cards such as www.tototek.com are always out of stock and charge high prices for these cards. The maximum RAM capacity for a Game Doctor SF6 is 128M but most people have one only with 32M or less installed. What's interesting though, is that if you have ever seen a Game Doctor SF6 32M or 64M RAM card, you will see that it uses very simple and cheap components. Has anybody tried to reproduce either the 32M or 64M RAM cards for use on a Game Doctor SF6? I want to find out if someone has a PCB trace schematic or compatible chip info that will help me reproduce these cards by hand to work on the SF6. Thanks for the help.
Here's a link to the 64M card: http://www.tototek.com/store/index.php?main_page=product_info&cPath=1_8_11&products_id=62

 

The information might be out there somewhere. Otherwise you or someone else will need to reverse engineer one of the boards. But it's still probably doable. But the market for such a product is certainly smaller than ever now since most people would rather use a Flash Cart with CF/SD cards.

 

Sourcing the supported, most likely out-of-production RAM chips might be the bigger issue. Couldn't find those pictured in the photo you linked, anyways.

 

There are still 5V DRAM chips available. The exact chips might be hard to find but that doesn't mean you can't find something that would work.

Also: http://gamedoctorhk.com/index.php?main_page=product_info&cPath=72_1_7_110&products_id=333

 

They used a lot of different types of RAM on this boards - but finding those ZIP RAM chips shown in that photo today would be a challenge.

Generally speaking, fast page DRAM is pretty interchangeable - you just need to be sure the number of row and column addresses match and that the controller generates at least as many refresh cycles as the chip needs (I.E. there is no problem using a 2K refresh cycle part with a controller than generates 4K cycles, but the other way around won't work).

 

I found a discussion thread on a website with a photo where someone took a 16M Game Doctor RAM card for the SF3 or SF6 that had 4 chips, swapped the chips and attached some wires to make it 32M or 64M. I spent an hour trying to find that thread again but couldn't find it.

 

If tototek has access to them then I don't see why anyone else can't have access to them. I couldn't find the chips in the photo either but I'm pretty sure that there are chips (with completely different markings) that perform the same function as those in the photo being sold somewhere like aliexpress or ebay.

 

I haven't made a 64m card for the SF6/7 but I've made similar memory cards for other devices. The process would be similar and straight forward. If you already have a smaller card you have most of the information you need. You could work out the rest with some simple tests. But this doesn't solve your stock or cost problems. That 64m card uses a 5117800 which you could get from several manufactures of they were sill made. But they aren't and are going to be hard to find and not going to save you much if any money.