Re: PLA replacement with 22V10

From: Michał Pleban <*lists_at_michau.name*> Date: Tue, 26 Mar 2013 16:35:29 +0100 Message-ID: <5151C041.9030503@michau.name> · lists_at_michau.name

Hello!

Ethan Dicks wrote:

> EPROM solutions are easy to implement - the PLA is essentially a
> "fast" (by 1982 standards) EPROM, not a PAL/GAL.

Well, internally, it's a PAL, not an EPROM ;-)

> I haven't memorized the access time of the 82S100, but an EPROM
> with an equivalent (or better) value will drop in there nicely.  ISTR it
> takes a 27C512 or so, but someone who's done it can certainly
> quote exact values.

Wasn't that actually a problem that a typical EPROM was _too_ fast
compared to the old PLA, for some critical timing in the C64?

Then there also is a problem that an EPROM modifies its outputs
differently than a PAL when the inputs start changing. A PAL, based on
logic equations, would behave in a much clearer way (and more similar to
the PLA, also based on equations) than EPROM (which is essentially a
huge lookup table). Wasn't that a problem in the C64, too?

Regards,
Michau.

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