[Coco] [Color Computer] 1M simms in Cloud9 SIMM upgrade kit
Paul T. Barton
idezilla at yahoo.com
Fri Jul 1 16:20:12 EDT 2005
You missed the part where I stated that
this CAS/before/RAS refresh was during
video (only!) and during HSync and
VSync. So, no slowdowns at all!
(Must have been on another email,
Check the URL:
Shows the timing from a TEK 'scope
during non-screen video time.
Paul :-) Happy Friday!
--- j_e_daggett <j_e_daggett at yahoo.com> wrote:
> --- In ColorComputer at yahoogroups.com, "Paul T.
> Barton" <idezilla at y...>
> > Mike,
> > Still, I think that it can be done.
> > By using CAS before RAS DRAM internal
> > The DRAMs keep their own internal counter
> > for this. Just swap RAS for CAS,
> > only during HSync and/or VSync.
> > I know that this works, I use it.
> > I could give out a partial schematic for
> > if you want a look-see.
> > Paul
> you can use CAS before RAS. During that period
> most page mode drams
> allowed ras only,cas before ras and hidden
> refresh. The problem I see
> with CAS before RAS is that you slow the aceess
> time down by 1/2. That
> is a 150 nS access time becomes a 225nS access
> time dram. The way I
> understand dram speed specs is that access time
> is determined from
> when the RAS line gose low and the data is
> ready for reading on the
> read cycle. CAS to data ready is half that of
> RAS to data ready.
> Putting the CAS before the RAS increases access
> time. In the computer
> world where speed is the holy grail, slowing
> down access is blasphemy.
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