17-07-2026, 10:48 AM
(13-07-2026, 10:29 PM)someone Wrote: Why is someone's replay 406 - Not Acceptable?SICK! I will try this out in my emulator > ultimate stress test. thanks someone!
(13-07-2026, 10:29 PM)someone Wrote: Why is someone's replay 406 - Not Acceptable?
Multi-tasking can be accomplished on a 128K DRAM microbee if you connect up a periodic interrupt to it such as VSYNC to the PIO Port B Bit 7.
You contain the hypervisor code in upper memory (8000-EFFF) and you have at your disposal 3 x 32K DRAM pages at 0000-7FFF to run each task.
One uses the periodic ISR to capture and switch CPU register sets and active DRAM memory page at 0000-7FFF.
One must take care to ensure that the R (Refresh) register is kept intact to ensure that the DRAM remains properly refreshed.
There is however inbuilt I/O resource management that needs be managed or considered.
Someone has demonstrated this concept driving 3 simultaneous instances of MWBASIC working this way on a 128K microbee.
The ROM image remains in upper memory at 8000, with 3 independent MWBASIC programs loaded into each 32K DRAM page.
There's a bit of EDASM & NET Shadow RAM (C000-EFFF) available for use for the hypervisor.
The Z80 RLD & RRD instructions are useful for multitasking because they are instructions that can perform 2 tasks simultaneously as not to create a "Race"condition. (i.e. Change the contents of a nominated memory location and change the contents of the Accumulator).
I.E. Stopping an unwanted Interrupt occurring between CPU instructions to cause a synchronisation issue.