6 MHz CPC - Revision history

Eto: /* Disadvantages */

2024-04-22T19:48:51Z

Disadvantages

← Older revision		Revision as of 19:48, 22 April 2024
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	* RAM should to be at least 160ns fast. Many CPCs only have 200ns RAM built-in. Replacing RAM requires to desolder the old RAM ICs.		* RAM should to be at least 160ns fast. Many CPCs only have 200ns RAM built-in. Replacing RAM requires to desolder the old RAM ICs.
	* Z80 might need being replaced by a 6MHz capable version. Pay attention to get a NMOS version of the Z80 as the CMOS version has different behavior for some undocumented but (rarely) used opcodes		* Z80 might need being replaced by a 6MHz capable version. Pay attention to get a NMOS version of the Z80 as the CMOS version has different behavior for some undocumented but (rarely) used opcodes
			* Sound must be reprogrammed / patched. No patches are publicly available.
	* The horizontal timing of the CRTC is affected. In order to get a stable image, you need to program register 0 at 95 (96 characters line) and Register 2 at 61 (centering for 40 characters default)		* The horizontal timing of the CRTC is affected. In order to get a stable image, you need to program register 0 at 95 (96 characters line) and Register 2 at 61 (centering for 40 characters default)
	* Pixels pitch is 66.7% of their original pitch.Theses pictures show this fact (320×200 mode 1 pixels with black border)		* Pixels are no longer square. Their pitch is 66.7% of their original pitch. Theses pictures show this fact (320×200 mode 1 pixels with black border)
	<gallery>		<gallery>
	Image:12062011055.JPG\|Original CPC @16Mhz		Image:12062011055.JPG\|Original CPC @16Mhz
	Image:12062011054.JPG\|Overclocked CPC @24Mhz		Image:12062011054.JPG\|Overclocked CPC @24Mhz
	</gallery>		</gallery>
	* Sound must be reprogrammed / patched. No patches are publicly available.

	== Software ==		== Software ==

Eto: /* Advantages */

2024-04-22T19:47:40Z

Advantages

← Older revision		Revision as of 19:47, 22 April 2024
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	== Advantages ==		== Advantages ==
	* Z80 ~~runs~~ with 6 MHz		* The whole computer runs 50% faster. Z80, Bus, RAM, CRTC run with 6 MHz, GateArray with 24MHz, Soundchip with 1.5MHz
	* Bus runs with ~~6 MHz~~		* FDC is 50% faster, Disc formats with 50% more sectors can be used after adjusting the DOS paramaters
	* FDC is 50% faster		* Sound that is programmed specifically for a 6MHz CPC can sound better than on a 4MHz CPC
	* Disc formats with 50% more sectors can be used		* Games can run more fluid
	* Sound can be better~~, since the PSG runs more quickly~~
	* Games run more fluid
	* Graphics are better, pixel are about 1/3 smaller in X		* Graphics are better, pixel are about 1/3 smaller in X
	* By adjusting the CRTC an higher frame rate can be used (75 Hz)		* By adjusting the CRTC an higher frame rate can be used (75 Hz)

Eto: /* Disadvantages */

2024-04-22T19:43:23Z

Disadvantages

← Older revision		Revision as of 19:43, 22 April 2024
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	== Disadvantages ==		== Disadvantages ==
	* ~~FDC~~ can't read ~~old~~ disc formats any longer. It is not possible to exchange discs with a 4MHz CPC.
			* Floppy disc controller also runs at 150% and can no longer read or write standard disc formats any longer
			** It is not possible to exchange discs with a 4MHz CPC.
			** a DOS must be used that allows to adjust disc parameters. Parados or CP/M are said to work. Unfortunately the parameters have never been documented or shared, so the values need to be figured out by anyone who tries the mod.
	* Not every hardware expansion is able to work with the 6 MHz bus speed. So also other options to load data and programs on a 6MHz CPC can become difficult.		* Not every hardware expansion is able to work with the 6 MHz bus speed. So also other options to load data and programs on a 6MHz CPC can become difficult.
	* Not all GateArrays will work with a 24MHz crystal		* Not all GateArrays will work with a 24MHz crystal
	* RAM should to be at least 160ns fast. Many CPCs only have 200ns RAM built-in		* RAM should to be at least 160ns fast. Many CPCs only have 200ns RAM built-in. Replacing RAM requires to desolder the old RAM ICs.
			* Z80 might need being replaced by a 6MHz capable version. Pay attention to get a NMOS version of the Z80 as the CMOS version has different behavior for some undocumented but (rarely) used opcodes
	* The horizontal timing of the CRTC is affected. In order to get a stable image, you need to program register 0 at 95 (96 characters line) and Register 2 at 61 (centering for 40 characters default)		* The horizontal timing of the CRTC is affected. In order to get a stable image, you need to program register 0 at 95 (96 characters line) and Register 2 at 61 (centering for 40 characters default)
	* Pixels pitch is 66.7% of their original pitch.Theses pictures show this fact (320×200 mode 1 pixels with black border)		* Pixels pitch is 66.7% of their original pitch.Theses pictures show this fact (320×200 mode 1 pixels with black border)
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	Image:12062011054.JPG\|Overclocked CPC @24Mhz		Image:12062011054.JPG\|Overclocked CPC @24Mhz
	</gallery>		</gallery>
	* Sound must be reprogrammed		* Sound must be reprogrammed / patched. No patches are publicly available.

	== Software ==		== Software ==

Eto: /* Disadvantages */

2024-04-22T19:27:20Z

Disadvantages

← Older revision		Revision as of 19:27, 22 April 2024
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	== Disadvantages ==		== Disadvantages ==
	* FDC can't read old disc formats any longer		* FDC can't read old disc formats any longer. It is not possible to exchange discs with a 4MHz CPC.
			* Not every hardware expansion is able to work with the 6 MHz bus speed. So also other options to load data and programs on a 6MHz CPC can become difficult.
			* Not all GateArrays will work with a 24MHz crystal
			* RAM should to be at least 160ns fast. Many CPCs only have 200ns RAM built-in
	* The horizontal timing of the CRTC is affected. In order to get a stable image, you need to program register 0 at 95 (96 characters line) and Register 2 at 61 (centering for 40 characters default)		* The horizontal timing of the CRTC is affected. In order to get a stable image, you need to program register 0 at 95 (96 characters line) and Register 2 at 61 (centering for 40 characters default)
	* Pixels pitch is 66.7% of their original pitch.Theses pictures show this fact (320×200 mode 1 pixels with black border)		* Pixels pitch is 66.7% of their original pitch.Theses pictures show this fact (320×200 mode 1 pixels with black border)
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	Image:12062011054.JPG\|Overclocked CPC @24Mhz		Image:12062011054.JPG\|Overclocked CPC @24Mhz
	</gallery>		</gallery>
	* Not every hardware expansion is able to work with the 6 MHz bus speed
	* Sound must be reprogrammed		* Sound must be reprogrammed

Scruss: /* Measurement of speed */ - speed test had syntax error - should be gosub, not goto

2020-11-14T20:14:00Z

Measurement of speed: - speed test had syntax error - should be gosub, not goto

← Older revision		Revision as of 20:14, 14 November 2020
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	10 i = 0		10 i = 0
	20 after 500 ~~goto~~ 100		20 after 500 gosub 100
	25 cls		25 cls
	30 i = i +1		30 i = i +1

Polluks at 18:04, 17 February 2016

2016-02-17T18:04:05Z

← Older revision		Revision as of 18:04, 17 February 2016
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	The ~~'''~~6 MHz~~'''~~ CPC is a [[DIY]] hardware modification which allows to run the [[CPC6128]] with a CPU speed of 6 MHz instead of the usual 4 MHz.		The 6 MHz CPC is a [[DIY]] hardware modification which allows to run the [[CPC6128]] with a CPU speed of 6 MHz instead of the usual 4 MHz.


	== Technic ==		== Technic ==
	The 16 MHz crystal of the CPC is replaced by a 24 MHz crystal. Both crystals should kept on the main board, but a switch (a DPDT type, switching both lines to both crystals is recommended) selects between them. Keep the wiring tidy and very short. You have to select the CPU and bus speed before you switch on the CPC. Switching the speed while the system is switched on is not advised.		The 16 MHz crystal of the CPC is replaced by a 24 MHz crystal. Both crystals should kept on the main board, but a switch (a DPDT type, switching both lines to both crystals is recommended) selects between them. Keep the wiring tidy and very short. You have to select the CPU and bus speed before you switch on the CPC. Switching the speed while the system is switched on is not advised.
	If you attempt this modification, it is at your own risk. None of the authors of this article can or will be held responsible for any damage to your CPC as a result of your DIY work.		'''If you attempt this modification, it is at your own risk. None of the authors of this article can or will be held responsible for any damage to your CPC as a result of your DIY work.'''

	== Advantages ==		== Advantages ==

Polluks at 18:00, 17 February 2016

2016-02-17T18:00:15Z

← Older revision		Revision as of 18:00, 17 February 2016
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	The 6 MHz CPC is a DIY hardware modification which allows to run the [[CPC6128]] with a CPU speed of 6 MHz instead of the usual 4 MHz.		The '''6 MHz''' CPC is a [[DIY]] hardware modification which allows to run the [[CPC6128]] with a CPU speed of 6 MHz instead of the usual 4 MHz.


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	== Software ==		== Software ==
	* A lot of games run well with 6 MHz. For example: Nebulus, StarFox, Starstrike and others.		* A lot of games run well with 6 MHz. For example: Nebulus, StarFox, Starstrike and others.
	* There is a 6 MHz version of FutureOS		* There is a 6 MHz version of [[FutureOS]]

	== Testing ==		== Testing ==

1024MAK at 12:08, 17 February 2016

2016-02-17T12:08:35Z

← Older revision		Revision as of 12:08, 17 February 2016
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	== Technic ==		== Technic ==
	The 16 MHz crystal of the CPC is replaced by a 24 MHz crystal. Both crystals should kept on the main board, but a switch (2 lines ~~at least, better 3~~) selects between them. You have to select the CPU and bus speed before you switch on the CPC. Switching the speed while the system is switched on is not advised.		The 16 MHz crystal of the CPC is replaced by a 24 MHz crystal. Both crystals should kept on the main board, but a switch (a DPDT type, switching both lines to both crystals is recommended) selects between them. Keep the wiring tidy and very short. You have to select the CPU and bus speed before you switch on the CPC. Switching the speed while the system is switched on is not advised.
	None of the authors of this article is responsible for ~~danger on~~ your CPC~~, in case you try to use this~~ DIY.		If you attempt this modification, it is at your own risk. None of the authors of this article can or will be held responsible for any damage to your CPC as a result of your DIY work.

	== Advantages ==		== Advantages ==
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	* A lot of games run well with 6 MHz. For example: Nebulus, StarFox, Starstrike and others.		* A lot of games run well with 6 MHz. For example: Nebulus, StarFox, Starstrike and others.
	* There is a 6 MHz version of FutureOS		* There is a 6 MHz version of FutureOS

			== Testing ==
			* Your CPC may work with the higher speed crystal if the rest of the system hardware is able to operate at this speed. You are more likely to be successful if the DRAM chips fitted to your machine are the higher speed versions (lower access time). Please refer to the relevant DRAM data sheet for details of the access time and on the type numbers and markings on the DRAM chips.

			*If any part of the hardware system is unable to properly function at the higher speed, likely symptoms of the hardware not being happy are failure to properly initialise to the start up screen. Or symptoms similar to a RAM fault.

			* This modification has been successful on some CPCs (manufactured with fast DRAMs) and verified with at least one CPC6128 produced in 1987.

	== Measurement of speed ==		== Measurement of speed ==
			* The CPU will operate at an increased speed proportional to the increased frequency of the crystal.

			* With a 24 MHz crystal, the 4 MHz clock (CPU speed) should be 6 MHz. This is a 50% speed increase.

	* ~~Some CPCs (manufactured with fast DRAMs) show a increase of speed by 50% (verified with at least one CPC6128 produced 1987).~~		* If your machine starts up okay, you can test the modification with this simple program :

	* In case of the ~~older DRAM type the speed improvement is only 16.7%.This has been tested~~ with this simple program :

	10 i = 0		10 i = 0
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	100 end		100 end

	Score is 258 on normal CPC versus 301 on 24 MHz ~~CPC~~.		Score is 258 on normal CPC versus 301 when using a CPC fitted with a 24 MHz crystal.

	(Theses results can be subject to discussion as we are not sure ~~interrupts~~ timing is ~~not~~ affected)		(Theses results can be subject to discussion as we are not sure how interrupt timing is affected).



	[[Category:DIY]][[Category:Hardware]]		[[Category:DIY]][[Category:Hardware]]

TFM: /* Measurement of speed */

2013-03-08T15:21:01Z

Measurement of speed

← Older revision		Revision as of 15:21, 8 March 2013
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	== Measurement of speed ==		== Measurement of speed ==

	* ~~This~~ speed improvement is 16.~~66667~~%.This has been tested with this simple program :
			* Some CPCs (manufactured with fast DRAMs) show a increase of speed by 50% (verified with at least one CPC6128 produced 1987).

			* In case of the older DRAM type the speed improvement is only 16.7%.This has been tested with this simple program :

	10 i = 0		10 i = 0

TFM: /* Advantages */

2013-03-06T17:03:21Z

Advantages

← Older revision		Revision as of 17:03, 6 March 2013
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	* Sound can be better, since the PSG runs more quickly		* Sound can be better, since the PSG runs more quickly
	* Games run more fluid		* Games run more fluid
			* Graphics are better, pixel are about 1/3 smaller in X
	* Graphics are better, pixel are about 1/3 smaller in X.		* By adjusting the CRTC an higher frame rate can be used (75 Hz)

	== Disadvantages ==		== Disadvantages ==