Re: Greg's questions
- To: MISC
- Subject: Re: Greg's questions
- From: Greg Alexander <galexand@xxxxxxx>
- Date: Wed, 05 Jul 2000 00:23:52 -0500
- In-Reply-To: Your message of "Sun, 02 Jul 2000 14:09:25 MST." <395FAF85.6582F075@UltraTechnology.com>
- Sender: galexand@xxxxxxxxxxxxxxxxxxxxxxxx
>The first 8 MuP21 chips were prototyed in ceramic packages.
>The production P21 was done in plastic. The plastic package
>intoduced a problem that was not present on the ceramic
>packages possibly due to increased inductance on the lead
>wires. The bottom line was that A! became marginal.
>
>Not all instructions take the same amount of current. Some
>required more power than others. A! is one of those. With
>the introduction of the plastic package some code that had
>worked on ceramic packages broke. It turned out that the
>cause was A! failing. It worked better in some slots than
>in others. The conservative fix was to preceed A! with a
>NOP. It might or might not be needed in each case but it
>provided a simple work around for the package introduced
>problem. I understand that the problem is not present
>on the plcc package. (shorter lead wires)
Do you mind if I include this description in the FAQ? I think it is a
good explanation of the issues surrounding the plastic vs. ceramic, and
A!. I don't really expect an answer, but it would be nice: is this the
same restriction Ting is referring to with the text "If T register was
changed in the previosu instructian, and A! is not in slot0, a nop is
needed before A! to let T stabilize." I ask because I want to know in
what situations we can remove the NOP.
Thanks.