At 10:35 AM 11/25/98 +0600, you wrote:
>As possible do protected mode?
>
>Why? For raising system reliability.
>
>Processor Must have 2 modes system and user. Bit "super"
>In the field of memories is conducted place which is only read in mode
>"user".
>If processor causes function of system that super=on. Access To registers of
>governing protection of memory possible in this mode only.
>Preceding mode returns When leaving
I have a slightly different idea. Allow write protect option for a part of
the RAM. Just like turbo R BIOS in DRAM, or ESE-SCC in ROM mode.
Advantages:
- not only system code can be protected, but all code (incl user code)
- probably simpler to implement,
because mode switching is not necessary for every system call
Disadvantages:
- system data is not protected
>Be
>also possibility to lengthen mapper before 16 bits of command Z80 will be
>able to change only younger byte, Z380 both using OUTW
If a programmer wants to use more than 4MB of memory (limit of 8-bit mapper
port), I don't think he'll want anything else than linear memory. In other
words, 16-bit mapper port has a low practical value.
Bye,
Maarten
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