Editing Atari 130XE Troubleshooting Guide (section)

== Memory & ROM Faults ==

=== RAM Configuration ===

The 130XE has two board configurations:

<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:90%; text-align:center;"
! Board !! RAM Chips !! Type !! Locations
|-
| CO70065/CO70067 (early) || 16 × 4164 || 64K×1 bit DRAM || U4–U19
|-
| C103579 (late) || 4 × 41464/MT4067 || 64K×4 bit DRAM || U4–U7
|}

The first 8 chips (or first 2 on late boards) form the base 64 KB; the remaining chips form the extended 64 KB bank-switched memory.

=== RAM Fault Diagnosis ===

<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
! Symptom !! Probable Cause !! Diagnostic Action
|-
| Black screen, no sound || Base RAM failure (lower bank) || Piggyback known-good DRAM on each chip; use RAM test cartridge
|-
| Garbage display, random characters || Partial RAM failure or address line fault || Touch-test each chip (failed chip runs hot); swap/test individually
|-
| Boots normally but extended RAM test fails || Extended bank RAM failure || Test with CheckXE or SALT; identify which bank fails
|-
| Random crashes during programs using extended RAM || Intermittent DRAM fault in extended bank, or EMMU failure || Run extended memory test; check EMMU (CO25953)
|-
| "ERROR" messages at boot || Partial base RAM failure || Run memory test cartridge to identify specific chip
|}

'''RAM diagnosis techniques:'''
# '''Touch test''' — run machine for 2 minutes, then carefully touch each DRAM. A failed chip often runs noticeably hotter than its neighbours.
# '''Piggyback test''' — place a known-good DRAM on top of a suspect chip, pins aligned. If the fault clears, the underlying chip is bad.
# '''Diagnostic cartridge''' — use SALT, Atari Diagnostics, or CheckXE to identify specific failed addresses.
# '''Logic probe''' — verify RAS, CAS, and data signals reach each DRAM. Missing signals indicate a trace break or failed FREDDIE.

=== ROM Fault Diagnosis ===

<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
! Symptom !! Probable Cause !! Action
|-
| No display, no boot activity || OS ROM (CO61598B) failure || Replace OS ROM; verify with known-good chip
|-
| Blue screen, no READY prompt || BASIC ROM (CO24947A) failure || Replace BASIC ROM
|-
| Boots cartridge software but not to BASIC || BASIC ROM bad or disabled || Check OPTION key is not stuck; replace BASIC ROM
|-
| Self-test screen but wrong characters || OS ROM partially corrupted || Replace OS ROM
|}

'''Note:''' Chinese-manufactured 130XEs shipped with a revised OS ROM that can cause compatibility issues with some software. Replacing with a standard CO61598B ROM resolves these problems.