Editing Atari 800XE Troubleshooting Guide (section)

== Voltage Test Points at IC Pins ==

Use the following table to verify that +5 V reaches all critical ICs. Measure with respect to board ground.

{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+'''IC Voltage Test Points (active HIGH = +5 V DC ±5%)'''
! IC !! Part Number !! Vcc Pin !! GND Pin !! Notes
|-
| CPU (Sally) || 6502C || Pin 8 || Pin 1, Pin 21 || Main processor
|-
| ANTIC || CO21698 (PAL) / CO21697 (NTSC) || Pin 40 || Pin 20 || Display list processor; generates CPU clock
|-
| GTIA || CO14889 (PAL) / CO14805 (NTSC) || Pin 24 || Pin 12 || Video output and colour generation
|-
| POKEY || CO12294 || Pin 23 || Pin 12 || Sound, keyboard, serial I/O, random number
|-
| PIA || CO14795 / 6520 || Pin 20 || Pin 1 || Joystick ports, peripheral control
|-
| FREDDIE || CO61991 / CO61922 || Pin 28 || Pin 14 || Memory controller and DRAM timing
|-
| OS ROM || 27128 or equivalent || Pin 28 || Pin 14 || 16 KB operating system
|-
| BASIC ROM || 2364 / 27C64 equiv. || Pin 28 || Pin 14 || 8 KB Atari BASIC Rev. C
|-
| RAM (4164) || 4164 (C070067 board) || Pin 8 || Pin 16 || 64K×1 DRAM (8 chips)
|-
| RAM (41464) || 41464 (CA200519 board) || Pin 18 || Pin 9 || 64K×4 DRAM (2 chips)
|}