AT&T 5620 questions
Jeffrey J Wieland
wieland at ea.ecn.purdue.edu
Sat Feb 17 01:44:22 AEST 1990
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 at ecn.purdue.edu
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