Overview
ReTuLa is a remake, using modern programmable logic, of the Tube ULA used in
Acorn Second Processors (which were introduced in 1984).
It is functionally identical to the original Tube ULA (both the Ferranti and
AMI issues), except for the following :
- DMA is not supported. This means that ReTuLa is incompatible with second
processors that use DMA. Only the 80186 co-processor for the Master does.
- The 'VDU FIFO' (FIFO 1 in parasite to host direction) is 1 byte deep
instead of 24. This seems a big difference, but, in general, it is completely
unnoticable. Only in very specific, theoretical cases, VDU throughput may
decrease by up to 4%.
Using ReTuLa
Using ReTuLa is no different than using the original Tube ULA.