Arnold4

The final cost down models came just before the release of the Amstrad plus.

The following information was tested by Gerald:

L4N6 pin

While it is connected to GND on the 6128, it is left unconnected on the 464 and seems to be internally pulled up.

In 464 mode :

  - the /ROM2 signal is always high : ROM7 selection is not handled on board.
  - the /CAS1 signal is always high :  RAM extension is not handled on board.

In 6128 mode :

  - the /ROM2 signal is handled on board.
  - the /CAS1 is handled on board, with the expected result of getting garbage instead of base RAM when using RAM selection other than C0
  - CPC does get stuck after displaying the copyright message and before the "BASIC 1.0" message.
    However, plugging a DDI1, even not powered solve the problem. ???

Extension RAM management

In 464 mode :

  - The RAMDIS signal IS taken into account. That mean that extension that does not force the MREQn will work. This include the SymbifaceII
  - The C3 mode is NOT supported, as on regular 464.

In 6128 mode :

  - Garbage all the way on extension RAM with no extension connected, as expected as no ram is there  ;D
  - With an extension, C3 is working as expected
  - adding 41464 in the alternate footprint and connected to CAS1 instead of CAS0 may transform the 464 in 4128  ;)

ROM7 and ROMDIS in 6128 mode

  - Well, no luck. ROMDIS does not prevent internal ROM7 to be selected
  - ROMDIS act as an output when ROM7 is selected (However I need to re-check that it is only happening on ROM 7)
  - ROMDIS act as the DDI ROMDIS as it is active even during ram access

10943-0

Bonus

  - on the following page, Gate Array and ASIC Pin-Outs - CPCWiki, pin 35 and 36 are undocumented.
  - on the PCB in the amendment service manual, these to pins goes to the FDC thru links : pin 35 to DATA, pin 36 to WINDOW

10945-1

  - Looks like amstrad was designing its own data separator and planned to use it on this version of the CPC. But As hinted in Arnold V specs - CPCWiki, it was not ready.