Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!ncar!oddjob!gargoyle!ddsw1!karl
From: karl@ddsw1.UUCP (Karl Denninger)
Newsgroups: comp.sys.tandy
Subject: Re: Model 4P with bad RAM
Summary: Tandy is WIERD
Message-ID: <1053@ddsw1.UUCP>
Date: 10 May 88 14:13:11 GMT
References: <4WUwM8y00XcSQ5LUE3@andrew.cmu.edu>
Reply-To: karl@ddsw1.UUCP (Karl Denninger)
Organization: Macro Computer Solutions, Inc., Mundelein, IL
Lines: 45

In article <4WUwM8y00XcSQ5LUE3@andrew.cmu.edu> dp1g+@andrew.cmu.edu (Demetri Patukas) writes:
>
>I have a Model 4P with a bad ram chip.
>
>After swapping some chips around I found the offending chip.
>
>So I thought, "no problem, just stick in a 4164 and off we go"
>
>Didn't work.
>
>So... can anyone tell me what the story is on the ram chips in the 4P?
>They have the number "8040665" stamped on them with both Motorola and
>Tandy logos.  I have a friend who used to do upgrades on these who
>claims that these should be the same as 4164's, but when I used a 4164
>it always read zero in that bit position.  Are these special Tandy
>rams?  Can I maybe bend some pins and use a 4164?

You can use a 4164 IF AND ONLY IF the refesh cycle spec is right.

The scoop is this -- some chips require 128 "refresh" cycles, and some
require "256".  The latter chips do NOT work in Model IVs.  This includes
nearly ALL of the American parts -- only the Jap stuff works at all.

An example of "Known good":
	Oki	4164

Texas Instruments 4164's, for example, while having the same part 
number (4164) do not work at all.


>Also, although my machine has sockets for a second set of 64K, my
>friend tells me that I will need a new PAL chip to get the machine to
>recognize it.  Where can I get the new PAL?  How much should I expect
>to pay?

If your Model IV is an older model (which tube, non-clustered arrows) then
you need the PAL for the second 64K.  Good luck finding one now-a-days...

If it's a new one (green w/cluster) then you only need to solder a wire or
two and put in the chips.  Somewhere I may still have the info around -- we
used to do these on a regular basis.

---
Karl Denninger                 |  Data: +1 312 566-8912
Macro Computer Solutions, Inc. | Voice: +1 312 566-8910
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