MCLK

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IMPROPER USAGE OF THIS PROGRAM MAY CAUSE DAMAGE TO YOUR COMPUTER SYSTEM.
PROCEED WITH CAUTION!!!
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MCLK is a program I wrote for Cirrus Logic video cards.  I have tested MCLK
on my Cirrus Logic GD-5428, but it should work on all GD-5424 cards and better
(GD-5426, 5428, 5429, 543x.)  These cards use a common clock programming
interface.

If you have the GD-5420 or GD-5422:
	Changes are slim of this program working.  Early revisions of these
chips did NOT possess a programmable MCLK (the MCLK was fixed.)

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HOW TO USE

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simply type the name of the program and a new MCLK register value.
For example,

	C:\MCLK 34

	(^^^ reprograms the MCLK to 60MHz.)

MCLK will tell you the ORIGINAL register value, and the new-value (as well
as the new calculated refresh frequency.)

Questions & Answers

Question:	I've boosted my MCLK, and my Cirrus card works fine in DOS,
		but it no longer works (locks up, doesn't redraw the screen)
		in Windows!
Answer:		The MCLK also drives the video accelerator.  Generally, DOS
		programs don't use the accelerator, but GUIs like Windows
		and OS/2 make heavy use of the accelerator.  Even if the
		DRAM can handle the higher refresh, the accelerator may not
		function properly with overly ambitious MCLK values.

		Solution?  Lower the MCLK.

Question:	In Windows, the screen doesn't refresh properly.  Sometimes
		I pull-down a window and instead of restoring the background,
		I get a blank rectangle under the window's former position.
		Or, when I scroll text, I get these funny screen jitters/lines.
Answer:		If your screen starts to "deteriorate" (dots left behind,
		screen "holes", etc.) most likely your DRAM is too slow for
		the new MCLK speed.

		Solution?  Lower the MCLK.

Question:	MCLK seems to work for a little while, but after rebooting,
		the benefits seem to evaporate.
Answer:		You should run MCLK whenver you re-boot your computer.  A
		good place to put it is in the autoexec.bat file.
		Also, if you have a VESA/DPMS (EPA Energy star) screen-saver
		active, be aware that the Cirrus's BIOS will re-program the
		MCLK.  I'm not sure if the BIOS resets the MCLK to a BIOS-
		stored value, or if the BIOS "remembers" the last MCLK value
		before it's re-written.

		Solution:  Put MCLK in autoexec.bat,
			   deactivate VESA/DPMS-based screen-savers.

Question:	Will this program work with other brands of video cards,
		besides Cirrus Logic?
Answer:		This program ONLY works with the Cirrus Logic GD-542x/543x
		family.  But many companies make products based on a Cirrus
		chipset.  (Cirrus just makes the chipset, not video boards
		for the end-user market.)  Here is a partial list:

		DIAMOND Speedstar Pro, Speedstar Pro SE, Speedstar 64
		ORCHID Kelvin 64
		STB, Compudyne, etc.

Questions?  Comments?  leave email to liaor@umich.edu