On Oct 24, 2:15 am, Antti <Antti.Luk...@googlemail.com> wrote:
> On 24 Okt., 07:50, Peter Alfke <al...@sbcglobal.net> wrote:
>
>
>
> > On Oct 23, 5:27 pm, "David Spencer" <davidmspen...@verizon.net> wrote:
>
> > > <MikeShepherd...@btinternet.com> wrote in message
>
> > >news:[email protected]. .
>
> > > > Although it's not expressed in DRAM specs and you wouldn't want to
> > > > rely on it, the effect of reducing refresh rate is to increase the
> > > > access time. I'm not up-to-date with DRAM technology, but my
> > > > experience with devices 30 years ago was that you could turn off
> > > > refresh (and all other access) for 10s or more without losing the
> > > > contents, provided you weren't pushing the device to its access time
> > > > limits.
>
> > > > So, it's not impossible that reducing refresh rate would have a use
> > > > (albeit outside the published device spec). But, as you suggest, it
> > > > would help if he would just tell us what he's trying to do.
>
> > > > Mike
>
> > > Although that may well be the case for asynchronous DRAMs (because the
> > > reduced charge in the memory cell capacitor would mean that the sense
> > > amplifier took longer to register the state), this would not be the case for
> > > SDRAM since this registers the outputs a fixed number of clocks after the
> > > access starts. If the underlying access time increased by too much then the
> > > data would just be wrong.
>
> > For certain addressing patterns, the refresh can be eliminated
> > alltogether, when the addressing sequence is such that all (used)
> > memory cells are naturally being read, and thus refreshed, within the
> > required time.
> > Peter Alfke- Zitierten Text ausblenden -
>
> > - Zitierten Text anzeigen -
>
> Sinclair ZX?
> at least some old Z80 homecomputers used refresh by video scan
>
> Antti

If I recall, the Apple II also refreshed its RAM this way, too.
-Dave Pollum