Path: utzoo!mnetor!uunet!lll-winken!lll-tis!oodis01!uplherc!sp7040!obie!wsccs!terry
From: terry@wsccs.UUCP (Every system needs one)
Newsgroups: comp.graphics
Subject: Re: 4014 stuff
Message-ID: <508@wsccs.UUCP>
Date: 30 Apr 88 03:37:01 GMT
References: <206300001@prism> <2007@rtech.UUCP>
Lines: 53

In article <2007@rtech.UUCP>, bobm@rtech.UUCP (Bob McQueer) writes:
> From article <206300001@prism>, by jms@prism.TMC.COM:
> > 
> > 	I'm pretty sure that there is no way to remove what is displayed.
> > This is the big disadvantage of storage tubes.  Refreshing the display
> > is done by clearing the screen......

This is right.

> I haven't seen a real storage tube for years, but I DO recall that
> there is a way to do a selective erase, essentially making your "pen"
> an "eraser" and allowing you to retrace what you've already drawn.

Uh, no.  Not on the 4014 in the other room, anyhow.

> I remember it as being one of about six modes in the Tek manual represented
> by circles in a state diagram showing the control sequences required
> to get from mode to mode.  I don't recall the sequence, and no longer
> have the appropriate documentation at my fingertips.

The doc's I have say "no way".  They say that as long as the storage tube
holds a charge, everywhere the beam hits STAYS LIT.  I think you are confusing
the 4014 with STMU's (Storage Tube Memory Units).  While it is POSSIBLE to
make the tube "forget" (sorta), it requires hardware not in the 4014's
schematics.

> Another interesting mode the storage tubes could be put into was a
> "write-through" mode in which your vectors would fade out in a fraction
> of a second.

Yes, this is possible with a storage tube.

> It was intended for the case where you had a dedicated machine to support
> refreshing the display continually.

No, again you mistake a 4014 for for an STMU.  That was not the intention.
Yes, you did have a machine who caused the refresh, but it wasn't for a
display reason... it was the first "dynamic RAM".

> These added modes may not be present on all 40xx devices - I remember it
> specifically from 4014's.

I would be suprised if ANY of the old storage-tube displays had this at all,
but especially so if it were an option I didn't know about.  I searched long
and hard for this years ago when I was rewriting plot-10 in C (back in my
student days).  It wasn't there.  Maybe your memory has selective erase? ;-)


| Terry Lambert           UUCP: ...{ decvax, ihnp4 } ...utah-cs!century!terry |
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