It is now possible to use either of the following:
* 1 x AM29F080 to get 1MB Flash Configuration
* 1 x HY628400A or AS6C4008 for 512KB SRAM (short the 512K solder jumper).
* 2 x 512K SRAM chips with a 74139 chip to get 1MB SRAM
I've just shipped my gerbers over to Shenzen for manufacturing a PCB - I'll report back with more news when the board arrive.
I started out with a 512K SRAM as a test (decoupling caps missing because I was still soldering when I took the pic). The RAM chips I used were about £2.35 each from ebay in quanties of 5. Initially my test was unsuccessful and I ended up beeping out every pin on the board but failing to find a problem. After scratching my head for a while, I moved the PCB over from the 3D-printed case I'd made into a pre-made case and all of my problems disappeared.
Next I moved upgraded the 512KB SRAM to 1MB by adding the extra chips and removing the solder bridge. After I got that working I moved onto a 1MB Flash. I hand soldered the SRAM ones to show that it's not too tricky, but used hot air for the Flash chip - The hot air solder stencil gives cleaner finish. As I needed some more cases, I 3D printed another one, and once again struggled to get things working until I disassembled another pre-made card. (Clearly I didn't learn the first time).
For the third card I'd run out of cases to disassemble so I had use a 3d-printed one. I made sure that there was absolutely no warping in the print and used a single wrap of tape to clamp the two halves of the case together near the card connector - This was the recipe for success - do not underestimate the role that the case plays in aligning and clamping the PCB and connector together - a fraction of a millimeter of misalignment or insufficient pressure on the connector contacts will lead to failure
With 2 x 1BM Flash cards, a 1MB RAM card and 512KB RAM/Flash onboard my Z88 can finally use all of its memory space. Every game and util that matters stored on Flash and enough RAM to have them all running too.
The designs are available for anyone who wants them from the z88-flash project on github, and there's a zip file up there with all of the gerbers and drill layers that you can send straight to a PCB shop through your web browser without ever needing to learn KiCAD.
Does your v1.1 design have the updated correct pin spacing? I'm interested in making some EPROM carts in addition to Fecn's flash cart.
Unfortunately the design posted by Xavsnap was using 1.27mm spacing, but if you grab it from my github instead you'll get the fixed version with 1.25mm spacing