C't 512 KB internal RAM expansion - Revision history

Eto at 14:10, 19 July 2023

2023-07-19T14:10:50Z

MacDeath at 01:23, 17 December 2010

2010-12-17T01:23:53Z

MacDeath at 01:17, 17 December 2010

2010-12-17T01:17:56Z

Nocash: /* PAL Source Code */

2010-05-08T15:52:50Z

‎PAL Source Code

Nocash: /* Compatibility Problems */

2010-05-08T15:49:06Z

‎Compatibility Problems

Nocash: /* Compatibility Problems */

2010-05-08T15:48:20Z

‎Compatibility Problems

Nocash: /* Compatibility Problems */

2010-05-08T15:12:36Z

‎Compatibility Problems

Nocash at 15:03, 8 May 2010

2010-05-08T15:03:07Z

Nocash at 14:51, 8 May 2010

2010-05-08T14:51:06Z

Nocash at 14:30, 8 May 2010

2010-05-08T14:30:45Z

Deprecated: The each() function is deprecated. This message will be suppressed on further calls in /mnt/cpcwiki-httpdocs/includes/diff/DairikiDiff.php on line 434

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 == Related hardware modifications ==
-* [http://cpcwiki.eu/forum/index.php/topic,662.msg7113.html#msg7113 Bank Swapper by Khany/Cherry-T] (less complex: bank-exchanging toggle, no memory expansion; 1993)
+* [[CPC_6320_/_CPC_6512_-_internal_320K_/_512K_for_CPC_6128|CPC 6320 / CPC 6512 (by eto) - similar logic, but fully standards compatible]]
 * [[CPC4MB| CPC4MB memory upgrade by Yarek]] (more advanced; 2005/2006)

← Older revision		Revision as of 01:23, 17 December 2010
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−	[[Category:DIY]]	+	[[Category:DIY]] [[Category:Memory expansions]]
	A project to upgrade a CPC6128 to 512K RAM (total), done by replacing the CPC6128's RAM chips, and its PAL banking chip, the project was released 1987 in german magazine ''c't Magazin''.		A project to upgrade a CPC6128 to 512K RAM (total), done by replacing the CPC6128's RAM chips, and its PAL banking chip, the project was released 1987 in german magazine ''c't Magazin''.

← Older revision		Revision as of 01:17, 17 December 2010
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		+	[[Category:DIY]]
	A project to upgrade a CPC6128 to 512K RAM (total), done by replacing the CPC6128's RAM chips, and its PAL banking chip, the project was released 1987 in german magazine ''c't Magazin''.		A project to upgrade a CPC6128 to 512K RAM (total), done by replacing the CPC6128's RAM chips, and its PAL banking chip, the project was released 1987 in german magazine ''c't Magazin''.

← Older revision		Revision as of 15:52, 8 May 2010
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	IF (GND) /IOWR=/IOWR ;dummy (do not output anything on this pin)		IF (GND) /IOWR=/IOWR ;dummy (do not output anything on this pin)
		+
		+	'''Note:''' For VRAM access, bank bits 2,3,4 are forced to zero (by above formulas), bank bit 0,1 are coming from the CRTC, passed directly to IC109 (without going through the PAL), so, the RAM banking affects only the CPU's memory accesses, not the CRTC's video memory accesses.

	Some notes on the syntax:		Some notes on the syntax:

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 * RAMDIS is not supported, not a problem in most cases, but won't work with some special types of expansion hardware, like [[Multiface II]].
 * The expansion seems to have been designed independently of [[Standard Memory Expansions]] like the dk'tronics one. So, there is no (intended) compatibility. However, both c't and dk'tronics are designed around the CPC6128 banking mechanism, so they do work similar in some ways. Namely, both can map expansion banks to 4000h..7FFFh, but there are several differences:
-** For the mapping to 4000h..7FFFh, dk'tronics uses values CCh..CFh, D4h..C7h, DCh..DFh, ... FCh..FFh whilst c't uses values C8h..DFh. Some of these values do overlap, providing some (unintended) semi-compatibility, but there's still one big difference: along with the above values, dk'tronics maps bank 3 to C000h..FFFFh, whilst c't maps bank 7 to that region.
+** For the mapping to 4000h..7FFFh, dk'tronics uses values CCh..CFh, D4h..C7h, DCh..DFh, ... FCh..FFh whilst c't uses values C8h..DFh. Some of these values do overlap, resulting in some (unintended) semi-compatibility, but there's still one big difference: along with the above values, dk'tronics maps bank 3 to C000h..FFFFh, whilst c't maps bank 7 to that region.
 == Memory Configurations ==

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 * The bank selection for CPU address 4000h..7FFFh does also affect bank bits0-1 for VRAM at 4000h..7FFFh; thus the CRTC may see bank 0-3 in that region (whilst, as far as known, on a normal CPC, it should always see bank 1 in that region).
 ** '''Notice''' the included sample program '''does''' seem to map VRAM to 4000h, whilst mapping expansion banks to 4000h at the same time. Theoretically, this should result in display glitches - unknown if/how/why the sample works [?]
 == Memory Configurations ==
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 * The "*" and "+" operators are meaning "* = AND", "+ = OR". The idea behind that confusing syntax was to make it "easier" to learn for people who are trained only in basic maths (the formulas do also work when treating *=multiply, and +=plus. For example: 1+0+1+1 = 3 = nonzero = true).
 * There must be some priority ordering in the formulas: Either * before +, or operations inside of a line before merging the results of the separate lines (in above examples, both ordering methods do work).
 == Scanned Article / Schematics ==

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 A project to upgrade a CPC6128 to 512K RAM (total), done by replacing the CPC6128's RAM chips, and its PAL banking chip, the project was released 1987 in german magazine ''c't Magazin''.
 == The Circuit ==
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 * RAMDIS is not supported, not a problem in most cases, but won't work with some special types of expansion hardware, like [[Multiface II]].
 * The bank selection for CPU address 4000h..7FFFh does also affect bank bits0-1 for VRAM at 4000h..7FFFh; thus the CRTC may see bank 0-3 in that region (whilst, as far as known, on a normal CPC, it should always see bank 1 in that region).
-== Missing Info ==
+== Memory Configurations ==
-* Unknown which banks are usable as VRAM
+The memory is controlled by OUT [7Fxxh],C0h..DFh instructions. Values C0h..C7h are working same as on normal CPC6128s. Values C8h..DFh do access the additional RAM banks (C8h..D3h when using the cut-down 320K upgrade variant).
-** The first four 16K bank are (probably) usuable as VRAM (as on all 64K CPC models)
-** The next four 16K bank are (hopefully) not usuable as VRAM (for CP/M+ compatibility, which uses them as Work RAM)
-** For further banks it's totally unknown if they are used as VRAM or not
-* Unknown if it's fully dk'tronics compatible, or more like incompletely implemented Inicron variant
-* Unknown what happens on accessing the unused region via OUT [7Fxxh],FCh..FFh
-−
-== Memory Configurations ==
    OUT [7Fxxh],C0h+...   0  1  2  3    4  5  6  7    8..31
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 == PAL Source Code ==
   D7D6 D0   D3   D4   D1   D2   NCAS A15  A14  GND  ;pin 1..10
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   IF (GND) /IOWR=/IOWR      ;dummy (do not output anything on this pin)
 == Newer Info ==

← Older revision		Revision as of 14:30, 8 May 2010
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−	A project to upgrade a CPC6128 to 512K RAM (total), done by replacing the CPC6128's RAM chips, and its PAL banking chip, the project was released 1987 in german IT magazine '''c't'''.	+	A project to upgrade a CPC6128 to 512K RAM (total), done by replacing the CPC6128's RAM chips, and its PAL banking chip, the project was released 1987 in german magazine ''c't Magazin''.

	== Technical ==		== Technical ==