That looks great Brian. Back in the day there was a device called RAMBO which was an option RAM which could be loaded by the machine with any ROM image. I don't know much about it, but it seems to me you are not far from re-creating it.
Kurt On Wed, Mar 11, 2020, at 1:32 PM, Brian K. White wrote: > > > machine has my REX in it because it's far easier to test ROM images with > > REX than to burn them to a ROM. > As an in-between level of fanciness, I just finished making a little > board that puts a 28C256 in a 27C256 socket. > > That could be used in the option rom socket of an 8201 or 8300, and the > system rom in 8201 but not 8300. It still requires an eprom programmer, > but at least you don't need a UV eraser and 20 minutes just to program > the chip. No test clip either. You just stick the chip in the programmer > and flash it. And it works like a plain rom, no possible compatibility > issues. > > https://oshpark.com/shared_projects/pYmaUMlK > > > And I'm waiting to test a PC-8300 system rom board. 8300 has an unusual > 1Mbit main rom, not 27C256, and not even 27C1000, but it's at least > pretty close to 27C1000, so it only takes a single jumper and a couple > pullup resistors to make the pinout switchable between the 8300 special > pinout and a pinout a programmer recognizes for the flash chip on the > board, so it too is programmable right in a programmer zif socket with > no uv or test clip. > > Well I made one version that needs 2 jumpers and 3 dupont wires to > program it, and another version that needs no wires and only a single > jumper. > I haven't made up my mind but I think I actually like the more > complicated one better for the admittedly dumb reason that it fits > entirely in the ROM0 DIP-28 socket, while the simpler and more practical > one is 32-pins, so it has 4 extra pins that hang off one end of the > socket. Works fine, doesn't hurt anything, easier for a user to get it > right. I don't want to annoy people who have actual OCD by saying those > 4 extra pins hanging off the end of the ROM0 socket sets off my OCD > but... I guess it does! > > https://oshpark.com/shared_projects/Bx4J3uAW > > https://oshpark.com/shared_projects/fAbPaZfG > > These aren't tested yet but they're on the way already. > -- > bkw >
