Re: Couple of //e Questions....

[dempson@actrix.gen.nz (David Empson)]

Jeff Jungblut <jeff@nospam.soapzone.com> wrote:

> > -Is there any drawback to using the Apple 1 meg memory card over the
> > AE one?
> 
> The Apple/RamFactor card was supposedly slower because it bankswitched
> 16K at a time instead of 64K like the RamWorks.  I never did any 
> benchmarks to verify that.

It doesn't bankswitch at all.  The Apple II Memory Expansion Card and
RamFactor operate on the principle of a single byte window into a large
area of memory, with an address register implemented in three I/O
locations.  Data is copied to or from the card by reading or writing the
data register, and the address register automatically increments after
each access.

This means that to use any data or code in these cards, it must be
copied out into normal memory, and copied back if any changes are made.

By comparison, the auxiliary slot memory cards work by switching most of
the address space between alternate 64K banks.  In many cases, data or
code in the card can be used directly without copying it elsewhere, but
there are situations that require copying the data to normal memory
(e.g. for display in the video buffers).

If data is being copied, then in theory the standard slot RAM cards can
be faster than the auxiliary slot ones, because a simpler addressing
mode can be used for accessing the data in the standard slot card.  e.g.
if you are copying data from the card, the source address is fixed and
the desintation address needs to be incremented, while with an auxiliary
card both the source and destination addresses would need to be
incremented.

On average, the auxiliary slot cards are probably a little faster, since
it is most likely that the data or code can be used in place.


The major advantage of the standard slot cards is that they can be used
as a RAM disk without requiring any patches to the operating system.  It
is also possible to boot from them.

Either type of card requires special support in an application which
wants to use it for data storage other than as a RAM disk (e.g.
AppleWorks desktop space).

Another potential advantage of the standard slot card is that it is much
easier to use all of the memory in the card.  Due to the memory layout
of the Apple II, it is only relatively easy to access 47.5KB out of each
64KB bank in an auxiliary slot card.  The rest requires more complex
bank switching.