Open2327RomAdapter V2

Thanks for your review and pictures, I'm glad you're happy with the board. It wasn't supposed to be used with that kind of switch, so that was a nice hack ;). The W27C512 for sure is Electrically Erasable (hence the "EE"), should you need to do that. Enjoy! :)

Hi SukkoPera My pleasure! Did you notice that the chip was in the CHAR ROM slot, it worked there. Also had it working the U3 BASIC ROM slot (no photo of that unfortunately)? I was just browsing the Internet and found this on the topic of what the "c" means in the eeproms. Taken from: https://www.classic-computers.org.nz/blog/2012-10-21-eproms.htm For your average vintage microcomputer, EPROMS can be recognised by their clear transparent windows, normally covered by some kind of label. Usually these ICs start with either a 27- or a 25- prefix but there may be others. After the prefix is a number such as 16, or 32, 64, 128 etc. This refers to how much data the EPROM can hold in kiloBITS. There are 8 kilobits in a kilobyte. A 2716 EPROM then can hold 2 kilobytes (k) of code. A 2732 can hold 4k and so on. Some EPROMS are low-power CMOS ICs. These have a "C" between the prefix and size number e.g. 27C32. CMOS EPROMS can be used in place of standard EPROMS in most cases. By the way I am a newbie in all this. Would you be kind enough to tell me a suitable multi switch that would suit you great PCB project? Thanks again... Take care

Thanks for the clarification about the C, at last I know! I usually use a simple SPDT switch, or a combination of them if I need more than 2 positions, which has never happened to me so far. About the char ROM position, it's only 4k if I recall correctly. I think I had a look and saw that it the adapter would work anyway because of how the extra address line is wired on the C64 mainboard, but if you want to be sure, just concatenate the image to itself and treat it as an 8k ROM, it will work.

Hi SukkoPera, thanks for the help on those SPDT switches.I will do some hunting on eBay. You are most correct about the 4kb CHAR ROM. I actually made a fortuitous mistake. I couldn't quite grasp the idea of concatenating the 8 x 8kb files into 1 x 64kb file. So I did a dodgy, I added 2x 4kb CHAR ROM files into the final concatenated file so that the whole final file added up to 64kb (There is actually Jiffydos for the 1541 disk drive in the 64kb file. I haven't tested this out yet. So in reality the chip has 9 images on it. One of the 8kb images is made from duplicating 2x 4kb CHAR ROM's). When I tested the chip with the appropriate switch configuration it worked! I suspect that it only really sees the 1st copy of the 4kb CHAR ROM file and the second one is only there to pad out file for correct positioning for the rest of the ROMS. Apologies for my lack of computer knowledge. What I'll do now you have me interested, I will mess around with putting more 4kb ROM's in pairs to make a valid 8kb ROM on a second chip I have and see if I can't replicate the initial results.A question for you. I see you have a 8kb and a separate 16kb cartridge project on this website. Would it be possible to run a mixture of both 16kb and 8kb ROM's on the 8kb version? I only say this because it has an ample amount of configurable switches. Thank you very much for your constructive feedback. Much appreciated.