The final cost down models came just before the release of the Amstrad plus.
The same chip was used within the late CPC464 and CPC6128.It performs the operations of the PAL used in the CPC6128, the Gate-Array used in older CPCs and the CRTC. =CRTC=
In CRTC terms it operates almost the same as the CRTC within the Plus ASIC.
=Costdown IC pinout information=
The following information relating to the pins of the IC was tested and verified by Gerald:
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 like AMSDOS ROM is handled on board6128/DDI1. When /EXT tied low, with the expected result of getting garbage instead of base RAM /ROM2 will be active when using RAM selection other than C0ROM7 is selected. When /EXT is floating (ie pulled up), /ROM2 will be active when ROM0 is selected.* CPC does 464 will get stuck after displaying the copyright message and before the "BASIC 1.0" messageas nothing is connected to /ROM2.* the /CAS1 is handled on board. On 464, expect garbage instead of base RAM when using RAM selection other than C0 and no RAM extension connected.
==Extension RAM management==
In 6128 mode :
* Garbage On a 464, garbage all the way on extension RAM with no extension connected, as expected as no ram is there ;D.* adding 41464 in the alternate footprint and connected to CAS1 instead of CAS0 may transform the 464 in 4128
* 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, as on regular 6128, unlike plus range.* ROMDIS act as an output when ROM7 is selected (However I need to re-check that it is TBC : only happening on ROM 7ROM7/0 ?)* ROMDIS act as the DDI DDI1 ROMDIS as it is active even during ram access 10943-0accesses.<br />The following picture shows the ROM detection routine : Selection of ROM7, followed by a read at 0xC000 where ROMDIS is active as well as /ROM2[[File:CPC464PREASIC 6128mode ROM7.png]]
==/EXP==
When the On a 464, when no DDI1 extension is not plugged, /EXP is pulled high, and . /ROM2 signal is in fact active as ROM0 and replace the BASIC. As no ROM is connected, it just crash !<br />On a 6128, /EXP is permanently tied to GND.
==Bonus==
* on In the following pageamendment service manual, Gate Array and ASIC Pin-Outs - CPCWiki, pin pins 35 and 36 are undocumented.* on However, according to the PCB in the amendment service manualmask, these to pins goes to the FDC thru through links : pin 35 to DATA, pin 36 to WINDOW 10945-1* Looks like amstrad 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[[Arnold_V_specs]], it was not ready. [[File:6128 PreAsic PCB.png]]<br /><br />= Enabling 6128 mode on 464 =Enabling the 6128 mode has two main advantages :* Being fully compatible with 6128 memory modes, mainly C3 mode when upper ROM is enabled.* On board memory can be increased to 128kb.<br />The compatibility modification, which is reversible, is achieved by soldering two wires:* one connecting IC101 pin 97 (L6N4) to ground, which configure the asic to work as a 6128* one connecting expansion port pin 48 (EXT/) to ground, preventing the asic to map the missing AMSDOS ROM in place of BASIC one.<br />The modifications are visible on the picture below [[File:Enable6128modeOn464PreAsic.jpg]] [[Category:Hardware]]