Editing IBM System/23 Datamaster (section)

== Connection to the IBM PC ==

The Datamaster's historical importance is its direct architectural lineage to the [[IBM PC (5150)|IBM PC]]. The following design elements were carried forward essentially unchanged:

{| class="wikitable styled-table" style="width:100%;"
|+'''Datamaster → IBM PC architectural carry-over'''
! Element !! Datamaster !! IBM PC
|-
| Expansion bus || 62-pin slots on backplane || Same 62-pin slots; '''only 5 signals changed'''
|-
| 8253 PIT, 8259 PIC || Same chips, same wiring || Identical
|-
| DMA || 8257 || 8237 (upgraded replacement)
|-
| RAM width || 9 bits (8 data + 1 parity) || Same
|-
| PSU "Power Good" signal || Present || Same signal, same pinout
|-
| PSU rail set || +5, +12, +24, −5, −12 V || +5, +12, −5, −12 V (24 V dropped because no built-in 8-inch drives)
|-
| Keyboard mechanism || 83-key capacitive Model F + 8048 || Same mechanism; serial interface instead of parallel
|-
| Character ROM and video format || 80 × 24 character cells || Same 80 × 24 character mode (MDA / CGA both inherit)
|-
| POST diagnostic || PID-1200, 2-digit hex codes via probe port || Ported and simplified to "POST"
|-
| Project home || Boca Raton ELS || Boca Raton "Project Chess"
|-
| Engineering team || Bill Sydnes (HW), Jack Sams (SW), David Bradley (POST) || Same Sydnes / Sams / Bradley
|}

Bradley's 1990 ''BYTE'' retrospective is explicit: "the diagnostics system was ported to the PC and simplified, and was renamed to POST." The Bits Passats community summary captures the broader point: "the early life of the IBM PC started as modifications on the Datamaster."