Vortex Expansions RAM card

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RAM expansions card from Vortex, mounted between CPC464 mainboard and CPU/Gate Array. It won't fit on CPC664, CPC6128, or CPC+ boards. The card is not compatible with the standard dk'tronics-sytle Standard Memory Expansions.

Sold in different sizes of RAM as SP 64, SP 128, SP 256, SP 320 and SP 512. Resulting in a maximum RAM size of 576K (64K internal, plus 512K external). The smaller SP64-SP320 versions can be upgraded to SP512 by mounting additional RAM chips in the spare sockets. There is also a cut-down version, SP 64/M, which contains only 64K RAM, no BOS ROM, and which isn't upgradable.

The expansion was available directly from Vortex (germany) and also from Screens Microcomputers (uk).

Usable under BASIC and CP/M:


BOS (Banked Operating System) RSX drivers are included on EPROM (mapped to ROM bank 6). Providing following features under BASIC:

  • Banked BASIC programs (using |GOTO, |GOSUB, |RETURN commands, for example: |GOTO,bank,line)
  • Pseudo Floppy (unlike a RAMDISK, this "floppy" can be accessed only via special RSX commands)
  • Debugger (aka Z80 Monitor) activated via |MON (v1.0) or |XM (v2.1)
  • Printer Spooler
  • Plus some extras like |FAST and |SLOW

Note: Some of the RSX commands are always available, some only after typing |BOS.


PATCH.COM is included on cassette. After copying the file from cassette to disk, it can be used to upgrade normal CP/M to support the expansion RAM. Providing following CP/M features:

  • 62K TPA
  • RAMDISK (unlike the BASIC Pseudo Floppy, this acts like a regular disk drive)
  • Printer Spooler

Note: There is a bug/problem with COPY.COM no longer working after installing PATCH.COM. A bugfix is listed in the appendix of the manual.



See Installing Vortex Expansion RAM.

Technical (very incomplete)

  • This section describes how you can access the RAM of the SP512.
  • The exact decoding (e.g. complete or partial) of I/O port addresses is not confirmed at this time.
  • The port addresses given are recommended and are those used by B.O.S..
I/O port &FBBD:
Bit	Function
7	Unknown
6	Unknown (Discology utility uses it - does it choose RAM in 32K blocks instead of 64K blocks??)
5	When 1, bits 2..0 define which 64k block of SP512 RAM to select. When 0, chooses internal 64K RAM of CPC464.
4	Unknown
3	Unknown
2..0	Used to choose the 64K block of the SP512 to select
I/O port &7F00:
Bit	Function
7	Set to 1
6	1 = make RAM visible in range &8000-&FFFF, 0 = make RAM visible in range &0000-&7FFF
5	Set to 1 to activate SP512. If bit 5 of &FBBD is 1 will select SP512 ram, otherwise select RAM of CPC464.
3	1 = Upper ROM disable, 0 = Upper ROM enable
2	1 = Lower ROM disable, 0 = lower ROM enable
1,0	Screen mode
  • When bit 5 is 0, then bit 6 is ignored.
  • When reading, ROM has priority over the RAM.



  • BOS (Vortex Banked Operating System) (RSX commands on built-in EPROM, mapped to ROM bank 6) (under BASIC, the RAM is used as program/data region, BASIC programs can |GOTO and |GOSUB to expansion banks)
  • Driver Cassette (includes PATCH.COM for upgrading CP/M to support the expansion RAM) (62K TPA, plus RAMDISK and printer SPOOLer)
  • Further patches - the manual contains additional patches for some BASIC and CP/M programs
  • Discology
  • RCPM (RAM CP/M, 1989-1990 by Günter Radestock) (RCPM is an alternative to the PATCH.COM from Vortex)
  • G-Paint 2.0 (by Günter Radestock)