Re: ZipGS question

["Bill Garber" <willy46pa@comcast.net>]

Charles Claypoole <1@rebbsNotrash.hopto.org> wrote in message
news:ZEvba.5$BG.2943174@newssvr11.news.prodigy.com...
> Ok, I tested today and found that if I remove the gsram+ altogether it
works
> in gsos at full speed..  i reinstalled gsram and it doesnt..

Try only having 5 mb in the ramGS+ and the one onboard leaves you with an
even 6 mb. Might just work and still give you enough for your other work.
;-)

> I read the manual and found that the gsram+ increases mem 6 megs.. I have
a
> total of 7megs including system memory..
>
> I tried removing the roms and it had the same results..  I have the
upgraded
> roms for the rom 3 installed too..
>
> Tried removing those just to see if it works, but it would crash too..
>
> Hate to run w/o it since i use it to do alot of ramdisk stuff.
>
> Charles
>
>
> "Rubywand" <rubywand@swbell.net> wrote in message
> 3E670861.C17CD0F1@swbell.net">news:3E670861.C17CD0F1@swbell.net...
> > Jeff Blakeney writes ...
> > >
> > > On Mon, 03 Mar 2003 11:50:07 GMT, Rubywand <rubywand@swbell.net>
> > > wrote:
> > >
> >  ....
> > >
> > > >     The method for addressing memory beyond 4MB on the cards is a
> > > >kludge; and, users are constantly experimenting to discover whether
> > > >or not some system problem is related to non-support for the extra
> > > >RAM.
> > >
> > > I wouldn't say it is a kludge.  If I remember correctly, Apple said
> > > that the max memory that the IIgs memory expansion slot can handle is
> > > 4 MB is because they only put address decoding circuitry on the
> > > motherboard to handle decoding 4 banks of RAM.  This is why, if your
> > > memory card uses those bank select lines, you are limited to 256 KB,
> > > 512 KB, 768 KB or 1MB if using 256 Kb memory chips or 1 MB, 2 MB, 3 MB
> > > or 4 MB if using 1 Mb memory chips.
> > >
> > > If the memory card doesn't bother using those bank select lines and
> > > instead decodes the memory address directly from the address lines
> > > then there is no reason why the memory expansion connector cannot be
> > > used to support up to 16 MB of memory.
> >  ....
> >
> >      It seems like the problem is that the complete address is only
> > available on the Address lines for up to 4MB-- you have 20 bits (1MB)
> > plus two lines to select 1 of 4 banks.
> >
> >      A workaround is to pick off bank information from the Data lines.
> > There's a good discussion in IIgs Technote #21 Glenn A. Baxter and
> > Jim Merritt ...
> >
> > >>
> > ....
> > Suppose a card were designed to latch the bank address directly from the
> data
> > bus with the rising edge of the PH2 clock signal.  It could use the bank
> > address to derive the proper RAM row address and never bother with CROW0
> and
> > CROW1 at all.  Directly latching the bank address would permit the card
to
> > accommodate any desired RAM arrangement in 64K increments, including an
> odd
> > number of rows.  Although the technique is valid during CPU cycles, it
> does
> > not work during DMA cycles since the FPI never emits the DMA bank
address
> onto
> > the data bus.  During DMA cycles, any card that tries to latch the bank
> > address directly, instead latches the bank address that was put on the
> data
> > bus during the last CPU cycle, which is probably the wrong value.
> > ....
> > <<
> >
> >      A possible fix could be some little module tacked onto the
> motherboard
> > which supplements the FPI and produces additional bank select lines.
> >
> >
> >
> > Rubywand
> >
>
>


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