[A83] Re: Randomization - r register
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[A83] Re: Randomization - r register
> What is the actual use of the r register in the z80?
> (I don't mean: "how can I use it...?")
It is used for refreshing of dynamic memory.
I don't exactly know how it does it, but I can tell you something about dynamic
memory:
Normally memory is build out of flip-flops:
tiny pieces of logic that can remember a value (1 or 0)
In the early days of computing, however, people tended to safe every penny on
hardware logic, since it was quite expensive, so another way of memory was
invented: dynamic memory.
One bit of dynamic memory is based on a capacitor holding a certain voltage.
An ideal cpacitor can hold a voltage indefinitely.
Generic image (ascii art):
---/\/\/\----------
|
-------
-------
|
-----------|-------
---
-
Now there are two problems:
- Every time you read out the "memory" unit, a little voltage sips out
of the capacitor
- Since it's not an ideal capacitor, it loses voltage over time.
To overcome these problems, dynamic memory is refreshed every few time units:
the voltage is replenished if neccessary.
Somehow the r register is connected to this, perhaps couting the number of
refreshes...
--Peter-Martjn
> SUCKER
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