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.