86 pin vs 100 pin
01-Oct-86 01:10:07
Sb: #34719-86 pin vs 100 pin
Fm: Dave Haynie/C128 Land 76703,2047
To: Michael Cohoon 70107,1670
This message turned up in search, but its forum couldn’t be identified from the original transcript, so it may not be linked into its thread.
No problem here. The 100 pin (Zorro) cards are based on the spec for an
expansion BOX. Every Amiga has the 86 pin edge card, and the bus that's
passed from box to box is always 86 pin. The Amiga system supports, in
hardware and software, two levels of expansion — the "box", which can be
your basic slotted expansion box, or just an add-on memory board, and the
"card", which is something that plugs into a box (I forget the exact Amiga
terms for these).
The extra pins on the 100 pin board are used for communications within the
box. You are correct in your observation that this specification came out
a while after the Amiga, but that has no impact on you Amiga itself. If
you buy a "box", make sure that if it has slots, they are 100 pin slots.
Every box will connect to the Amiga OK. There were a few cards made with 86
pins by some early developers; as far as I've heard, these will fit in a
100 pin slot OK (though I'm not sure how immune to slipping they're likely
to be … the 100 pin slots have no mechanical stops at the 86 pin mark).
As for RAM, the term "no wait states" means that the 68000 will never slow
down when accessing this memory. Most memory expansions use dynamic RAM
devices that must have their internal charges in every memory location
refreshed evey so often, usually once every 4 milliseconds or so. A wait
state can occur if a board decides to refresh this memory at the same time
the 68000 needs it.
There are various methods of design that will insure that this situation
never happens, though this may cause an increase in the price of the
board. Even a board that has potential wait states isn't likely to slow
you down that much, but every bit of speed is a nice thing to have. -Hazy