Re: 17 Meg //e

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

Charles Stephens <devnull@dobbs.eng.sun.com> wrote:

> Well there is a downside to slinky.  Basically it had a limited access
> window whereas the AUX slot memory cards could be mapped to several
> large regions in memory.  This means that getting stuff in and out of
> the slinky card is slower than bank switching.

I disagree with that statement.  The slinky cards have an
auto-incrementing address register, which means that streaming data in
or out of them is _faster_ than copying data between two memory blocks
in main RAM (the CPU only has to keep track of one RAM address and a
count, instead of two RAM addresses and a count).

This advantage may be negated by the overhead of a SmartPort call for
each transfer.

In tightly limited circumstances, copying data between main memory and
an auxiliary slot card bank could be about the same speed as with a
slinky: if the source and destination address within the bank is the
same, then only one pointer needs to be updated.

The auxiliary slot card's big advantage is that it can execute code
directly from other banks, rather than having to copy code into main RAM
first.  Data within the current bank can also be randomly accessed,
which is inefficient with the slinky card.

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand