Oric goes 816!

Post date: 17-Jan-2010 18:03:47

We found we had an Oric, so... 17 unscrewings later, next step was an optimistic one, to put in the Level1B board with the possibility of running up to 8MHz. But that didn't work.

After a quick detour (of several days) to fixup a wobbly keyboard connector, Rich tried the Level0 board - and it did work!

More images in our album [dead link...]

What does Level0 mean? It means you have a 65816, but clocked at the original host speed and with no additional memory and no CPLD for extra functionality. So you get benefits like the stack-relative addressing, a B register, some useful extra instructions.

Why did the Level1B fail? We don't yet know, but the Oric has an unusual clocking story. Instead of the usual (one phase for video access, hidden in the normal PHI1 of the 6502, leaving PHI2 for CPU access) we have a stretched PHI1 with two video accesses, and then PHI2 as normal. Although we still can't see how this would affect the Level1B.

Has this been done before? Why, of course.

One other difficulty: while the Oric has a socketed ROM, which is promising for other kinds of adventures with an 816, it has a soldered-in 6502. So that had to be sacrificed (easier than desoldering)