No game quick changes allowed?

[Simple Sam]

I decided to upgrade my MPU to a 504B so I picked up a board and a MML card; I already had another game and sound SIMM.  Since I was a little nervous about making a mistake I also picked up the SG000363 and VX011GX1 chips (same as on my existing MPU).  I assembled the whole thing, did the clear and key chip thing, and happily, it worked!  I didn't change the strips because I wasn't ready for that.  When I put the old MPU assembly back in (remember, I didn't touch it), I got a "call attendant" error message.  I thought I would just be able to have a MPU already set up for another game and just quickly change it out; is that not possible?

[foster]

there is a MPU ID that is unique for each MPU.
Yes you can change MPU's but you have to clear the error just like when you change any of the EPROM's

[PLUNGER BOY]

Changing the mpu will give you a call attendant error open the door it will give ram error turn the key 3 times until it tells you to push the mpu button and close the door it should initialize and start up you may have to do this 1 or more times . I think i have done this before ? P.B.

[Simple Sam]

I wasn't successful using the MPU button and decided it wasn't that much effort to clear and key it again so I am back in business.  Maybe I will poke around a little later.