Circuit diagram for single ROM board

[martin464]

Guys, I'd really like to replace the OS ROM with a small board containing a single EPROM
So it could be hardcoded just for this purpose no need to select other slots
Meaning when switched on it boots off it

Would really be appreciated if anyone could craft a circuit diagram for this
(this is for a 464 if it makes a difference)

A pass through of the expansion probably not needed was planning to add a couple of IDC sockets off in parallel for other devices to plug in

What you think? Thanks for any ideas!

[pelrun]

ACU did one back in the day...

https://www.cpcwiki.eu/index.php/The_ACU_Romchanger

[Richard_Lloyd]

There's one by Bryce on the Wiki.

https://www.cpcwiki.eu/index.php/LowerROM

[Bryce]

Hi,
   as Richard suggested, my Lower ROMBoard. It has a pass-through which is an important part of the circuit, because it's not a simple pass-through, otherwise it would block all other expansions. I don't think I have any of these boards left over, but it's a simple circuit to make.

Bryce.

[martin464]

damn, that's great. i'll have a go at this about time i did some soldering
if this project works it's gonna be my ideal 464 heh heh

will a 16k chip work ok in there? only need a few k and i got a spare one

[Bryce]

I designed it for a 64k ROM so that you can have two different systems on one chip and switch between them. You could use a 32k ROM for just one system, but because the upper and lower ROM's needs to match, you will need at least 32k for it to work.

Bryce.