wieland@ea.ecn.purdue.edu (Jeffrey J Wieland) (02/16/90)
I have a couple of questions about the AT&T 5620 terminal:
1. I tried to upgrade the memory in mine by replacing the 64K ram
chips the 256K ram chips. It passes the self test on start up,
and when I go into cip, cip sees the additional memory (shows
over 400K free). However, cip will crash after 10 minutes or
so. Tek4014 will crash also. The errors I get look like the
following:
Normal Exception #0x4 at 0x72B379
Normal Exception #0x2 at 0x0
Normal exception 4 is "invalid descriptor", which means that
there was an attempt to execute an instruction with an invalid
operand.
Normal exception 2 is "illegal" opcode.
It seems that memory errors are ocurring. I've tried replacing
the 256K chips -- it doesn't seem to make any difference. The
256K drams are just standard 150 nanosecond parts.
Do the dip switches on the processor board need to be changed?
What are they for, anyway? Maybe someone who has the "5620
Dot-Mapped Display General Technical Reference" manual could
tell me this.
2. What is the parallel i/o port for? Did anything actually ever
use it?
--
Jeff Wieland
wieland@ecn.purdue.edugwyn@smoke.BRL.MIL (Doug Gwyn) (02/17/90)
In article <19704@ea.ecn.purdue.edu> wieland@ea.ecn.purdue.edu (Jeffrey J Wieland) writes: >I have a couple of questions about the AT&T 5620 terminal: >1. I tried to upgrade the memory in mine by replacing the 64K ram > chips the 256K ram chips. > It seems that memory errors are ocurring. I've tried replacing > the 256K chips -- it doesn't seem to make any difference. The > 256K drams are just standard 150 nanosecond parts. > Do the dip switches on the processor board need to be changed? > What are they for, anyway? Somebody ran off with my 5620 shop manual and Teletype upgrade instruction sheets, so I can't be as precise as I would like to be in my response. However, as I recall you also need to replace a timing chip (maybe a 74LS125?) in the corner of the logic board with a faster version. I don't know whether 150ns DRAM is sufficiently fast but from your symptoms it sounds like it must be. I don't think the DIP switches are related to RAM configuration, just ROM. If you upgrade from 8;7;3 to 8;7;5 firmware, the new ROMs have twice as much data and the DIP switches have to be changed for the terminal to work. >2. What is the parallel i/o port for? Did anything actually ever > use it? I've never heard of any use for it.
david@ms.uky.edu (David Herron -- a slipped disk) (02/18/90)
The official AT&T 1Meg upgrade for 5620's simply has you replace two things
memory chips with 40256's
one of the 74xxx chips with a slightly different version.
(don't remember details; I think the new chip was an LS part)
Ages ago I had someone tell me they simply replaced the memory chips
and everything just worked.
Ages++ ago I tried using the official 1Meg upgrade to upgrade "my" 5620.
Oops.. didn't work. And we didn't try tracking down what was wrong.
--
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<- Now arrived at a nameserver near you: david@davids.mmdf.comgwyn@smoke.BRL.MIL (Doug Gwyn) (02/20/90)
In article <14223@s.ms.uky.edu> david@ms.uky.edu (David Herron -- a slipped disk) writes: >Ages ago I had someone tell me they simply replaced the memory chips >and everything just worked. I think some newer 5620s already had faster timing chips on board, so that chip didn't need replacement. >Ages++ ago I tried using the official 1Meg upgrade to upgrade "my" 5620. >Oops.. didn't work. And we didn't try tracking down what was wrong. It worked fine for us, on a couple of dozen 5620s. Maybe you didn't ground yourself before working with the static-sensitive chips?