09-04-2013, 09:36 AM
boriel Wrote:This is awesome. I only own a Speccy 48K, +2 (grey) and +2A.
What's the difference with +2B? Why the incompatibility?
In all probability your +2A is actually a +2B. The real +2A is pretty rare. The +2A has the same motherboard as the +3 but partially depopulated. The +2B has the cut-down motherboard. The +2B fixes the corrupt sound on the +3/+2A. So for people with a +3/+2A they will need to do the sound fix or the sound will be distorted. For people with the toast rack or grey +2 (ULA 128s) they will need to replace the HAL with a GAL from Velesoft that changes the contention to match the +3/+2A/+2B (ASIC 128s). The ULA 128s contend every I/O access and different RAM pages. This doesn't always leave enough t-states per frame to keep the engine going with a large number of sprites, and the ZXodus][Engine pushes the machine to its limits.