Kurzweil PC88 - Page 29

Chapter 2 Diagnostics
Marge Test
This test confirms that Marge is installed properly and
successfully interfacing with the microprocessor.
Failure of this test indicates a problem with Marge
(U2), associated selection circuitry (74LS164, U16) or traces
linking Marge to U1 and U21.
While this test is in progress, one should see activity
on Marge's chip select and write enable pins. Also check
the address and data pins.
Delay RAM Test
This test writes to the entire delay RAM space and
verifies that the writing was successful. Marge must be
operational before this test can pass, since the processor
must use Marge to access the delay RAM.
Failure of this test indicates a failure of Marge or the
delay RAM (U9 and U10).
While this test loops on failure, one should see
periodic activity of the RAS, CAS, and write enable pins
on each DRAM chip. Also look at the address and data
pins.
LCD Test
The LCD Test writes a group of characters to the LCD
and verifies that the same characters can be read back
again. There is a 1 second pause between the times that
the characters are written and read so that the user can
visually inspect the pattern.
A failure of this test indicates a problem with the LCD
or the related address decoding circuitry (74LS245, U3;
74HCU04, U8).
PC88 Service Manual
2-11