🚀 go-pugleaf

In a fit of anal-retentive self-righteousness I wrote:

> The CPU puts the address up, then some time later that only depends on the
> CPU's internal timing it samples the data lines.  IF THE MEMORY WAS TOO SLOW
> AND DIDN'T GET THE DATA UP IN TIME, TOUGH NOOGIES, *NOBODY NOTICES*!!!

In article <GILHAM.90...@cassius.csl.sri.com> gil...@csl.sri.com
(Fred Gilham) writes:

> Actually this is not strictly true either.  A lot depends on the
> architecture.  For example, the 68000 architecture requires that the
> memory acknowledge the access request before the operation continues.
> Alternatively, many processors have a ``wait-state'' line where the
> memory can tell the processor to execute wait states until the memory
> is ready.  Thus a memory system can syncronize with the processor by
> slowing it down.

This is quite true, however, it will be the memory controller that does one
of these two things, not the memory chips themselves.  In all the personal
computers (i.e. those in which uneducated users will be buying and inserting
memory chips of different speeds) there is no separate memory controller.
The memory access logic is integrated with the processor on the CPU card.

There may well be memory cards where a dip switch or other configuration
setting can tell the memory to ask for additional time, but in any case it
will definitely be more than just putting in the faster chips.  There is
no way for the memory controller to know how fast the chips are unless you
tell it somehow.

Just replacing 150ns chips with 70ns chips will not make your computer run
any faster...
-- 
Sig     DS.L    ('ZBen')       ; Ben Cranston <zb...@Trantor.UMD.EDU>
* Network Infrastructures Group, Computer Science Center
* University of Maryland at College Park
* of Ulm