Editing Atari 520ST+ (section)

== Architecture ==

The 520ST+ is architecturally identical to the [[Atari 520ST]], differing only in RAM capacity:

* '''CPU:''' Motorola MC68000P8 or MC68000FN8 @ 8.00 MHz
* '''Architecture:''' 16/32-bit (32-bit internal, 16-bit external data bus, 24-bit address bus)
* '''RAM:''' 1 MB, using 16× 256k×4 or equivalent DRAM configuration
* '''ROM:''' 192 KB TOS (TOS 1.00 in 6× 32 KB ROMs, or TOS 1.02 in 2× 128 KB ROMs on later units)
* '''Custom ICs:''' Shifter (C025914), GLUE (C025915), MMU (C025912), DMA (C025913) — identical to standard ST

=== Major ICs ===

<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable"
! Function !! Part Number !! Notes
|-
| CPU || MC68000P8 / MC68000FN8 || 8 MHz, DIP-64 or PLCC-68
|-
| Video Shifter || C025914-38 || Pixel serialiser
|-
| GLUE || C025915-38A || Bus timing, address decode
|-
| MMU || C025912-38 / C100109 || DRAM controller; later revision on some boards
|-
| DMA Controller || C025913-38 || ACSI/floppy DMA
|-
| FDC || WD1772-00-02 || Floppy disk controller
|-
| MFP || MC68901 || Timers, interrupts, UART
|-
| ACIA (×2) || MC6850 || Keyboard/IKBD and MIDI
|-
| Sound/PIO || YM2149F || 3-voice PSG + I/O
|-
| RS-232 drivers || MC1488 / MC1489 || Serial port level conversion
|}