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Old 08-29-2015, 10:37 AM   #1
trodas
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Question 12MHz clock generator for the Holtek HT6542b

I wonder, if someone can suggest me relatively simple clock generator, that will produce 12MHz clock for the Holtek HT6542b PS/2 keyboard and mouse controller:
http://www.alldatasheet.com/datashee...K/HT6542B.html

Likely this will need some 12MHz oscilator, then a gate with will switch the clock... and that should be it. Or I'm wrong?

Ideas welcome!
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Old 08-29-2015, 01:47 PM   #2
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Default Re: 12MHz clock generator for the Holtek HT6542b

just get a crystal.
the chip has a built in clock driver.

put the crystal between the OSC0 and OSC1.

it's at the bottom of page 6 and 7
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Old 08-30-2015, 05:53 AM   #3
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Default Re: 12MHz clock generator for the Holtek HT6542b

But... I never worked with crystal, so... a little basic could be handy.

First:
What crystal? 12MHz probably, but... search on Digikey for what to get crystals? Are some good brands? Could I get small yet reliable and stable one...?

I mean reasonably small, that I can glue it on top of the Holtek chip, witch is rather big suxxka:




Second:
Witch leg go where? I mean... last time I worked with crystals was overclocking on Amiga. CPU accelerator from Phase5 Blizzard 1260 got crystal with 4 legs on it, relatively big (I say about 12x6x5mm in size). All I did is to desolder it, solder a socket there and order custom made crystals from 60 to 68MHz to determine witch one will still work. But even if the crystal have only 2 legs, then still I have no idea, witch leg go where.

Does it even matter? The looks in the drawing suggest, that maybe it does not matter at all, but since I never work with crystals, I rather ask 100 stupid questions first...
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Last edited by trodas; 08-30-2015 at 05:54 AM..
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Old 08-30-2015, 06:41 AM   #4
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Default Re: 12MHz clock generator for the Holtek HT6542b

crystals have 2 legs, the amiga used an oscillator.

put the crystal legs on the OSC pins of the chip.
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Old 08-30-2015, 09:06 AM   #5
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Red face Re: 12MHz clock generator for the Holtek HT6542b

So, when I take this 12MHz crystal:
http://www.gme.cz/krystal-hc49-u-q-12mhz-p131-012

...and solder it on the legs 2 and 3 (while separating them from the mainboard first by cut & bend up), I should be good to go?

No difference of witch pins go where? I keep asking just to be absolutely sure.

...

And Amiga used this:


It does not look "all that different" to me?
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Old 08-30-2015, 11:36 AM   #6
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Default Re: 12MHz clock generator for the Holtek HT6542b

where is it on that motherboard?
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Old 09-01-2015, 03:44 AM   #7
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Default Re: 12MHz clock generator for the Holtek HT6542b

The motherboard has an ICS9169CJ-27 clock generator at U21.

http://web.archive.org/web/200009190...f/9169c-27.pdf

This chip derives the CPU, BUS, 48MHz and 24MHz clocks from the 14.31818 MHz reference crystal. I suspect that the HT6542B's 12MHz clock is generated from either the 24MHz or 48MHz clock via a simple divider in the Intel chipset.

http://web.archive.org/web/199805222...uter/6542B.PDF

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Old 09-01-2015, 03:59 AM   #8
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Default Re: 12MHz clock generator for the Holtek HT6542b

that wasnt what i asked.

are you adding that chip, or is the board already designed to take it?
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Old 09-01-2015, 07:16 AM   #9
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Wink Re: 12MHz clock generator for the Holtek HT6542b

Crystals (I take two) arived today, so I ask again for reply on this:

Quote:
So, when I take this 12MHz crystal:
http://www.gme.cz/krystal-hc49-u-q-12mhz-p131-012
...and solder it on the legs 2 and 3 (while separating them from the mainboard first by cut & bend up), I should be good to go? No difference of witch pins go where? I keep asking just to be absolutely sure.
...

stj -
Quote:
where is it on that motherboard?
Where is what? You gotta say what do you mean by the "it." If you mean the 4 legs crystal I posted, then I mentioned that such things are used on Amiga Blizzard 1260 card:
Quote:
last time I worked with crystals was overclocking on Amiga. CPU accelerator from Phase5 Blizzard 1260 got crystal with 4 legs - Amiga used this:
So if you asking about the Blizzard 1260 CPU card for Amiga 1200, then it was there:
http://amiga.resource.cx/photos/gall...zard1260-4.jpg

If you asking about the mainboard - no, there it is NOT. There is only the 14.3MHz reference clock crystal and the small crystal for the clock near the battery. No more crystals. You can see that on the hi-res picture.

But I plan on adding one on the top of the Holtek chip... if you confirm that the pins not matter, then I solder and glue that thing on the microcontroller, so the board will have 3rd crystal


fzabkar -
Quote:
The motherboard has an ICS9169CJ-27 clock generator at U21.
Indeed. And since there is no way to software control of the chip:
"
Quote:
do not have a System Management Bus connection or the FSB could not be set via System Management Bus. So there is and will be no program that supports these PLL's!!! There is absolutely no chance!
"
http://www.cpufsb.de/FSB.HTM

...then what makes me wonder is this:



If I understand that right, then it is possible to lock on the PCI bus to 32MHz regardless of the FSB clock. That would allow me to overclock into 83MHz FSB w/o problems (unreliable IDE controller) on the PCI bus...!

Selecting BSEL = 0 could be pretty cool mod and I cannot understand, why Asus did not do it already. When using PLL chip that can do PCI lock - it is almost a crime not to utilize that...!
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Old 09-01-2015, 11:46 AM   #10
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Default Re: 12MHz clock generator for the Holtek HT6542b

crystal pins are the same, direction does not matter.
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Old 09-01-2015, 02:22 PM   #11
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Default Re: 12MHz clock generator for the Holtek HT6542b

I don't understand the reason for the crystal mod. The Holtek chip's frequency would be fixed at 12MHz, independent of any FS/BSEL settings.
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Old 09-01-2015, 05:30 PM   #12
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Default Re: 12MHz clock generator for the Holtek HT6542b

i dontt undersand any of it!
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Old 09-01-2015, 06:35 PM   #13
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Wink Re: 12MHz clock generator for the Holtek HT6542b

fzabkar -
Quote:
I don't understand the reason for the crystal mod. The Holtek chip's frequency would be fixed at 12MHz, independent of any FS/BSEL settings.
Reason? Simple. Keyboard and mouse fail to work, when I use the ref/2 FSB clock of 7.14MHz. That is why and adding the crystal aim to fix this problem, so the Holtek clock will be entierly independent of the FSB, hence no more problems at "superlow" FSB clocks.

Last edited by trodas; 09-01-2015 at 06:36 PM..
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Old 09-03-2015, 02:14 PM   #14
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Default Re: 12MHz clock generator for the Holtek HT6542b

Slight bump for answers?
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Old 09-03-2015, 06:05 PM   #15
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Default Re: 12MHz clock generator for the Holtek HT6542b

Your proposal to lift the OSC pins and solder a HC49 crystal to them seems OK to me. Otherwise I'm not sure what answer you are expecting.
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Old 09-03-2015, 07:21 PM   #16
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Default Re: 12MHz clock generator for the Holtek HT6542b

exactly.
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Old 09-06-2015, 11:50 AM   #17
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Exclamation Re: 12MHz clock generator for the Holtek HT6542b

Reporting sucess! I desoldered the complete PS/2 controller Holtek HT6542b from the board, bend up pins 2 and 3, soldered it back and soldered a 12MHz crystal on it, gluing it later to it by epoxide:



(preliminary pics, I did cleared the excessive amounts of tin meanwhile)

And the keyboard & mice worked nicely on all the FSB settings the board can officially (50,55, 60, 66, 75, 83MHz) offer and - what is most important - it does work nicely on the ref /2 superslow 7.14MHz FSB clock!!!

As great bonus, the computer seems to work *MUCH* faster on the superslow clocks. And what is even more important, the 83MHz settings is working well stable for SuperPi 1M: http://hwbot.org/submission/2970070_

...and it is currently running the SuperPi 32M test at around half and it is therefore pretty stable (SuperPi 32M total run time is about 14-15h (it was 17h on 112.5MHz), so 7h under 100% load stable...

...

I should note that I did not tried 83MHz before, because my friend, for who I was recapping that board back in 2008 and he give it back to me recently, said that 83MHz cannot work stable for him, no matter what.

...

What if that tweak I made actually make it working? I was ready to try the BSEL = 0 setting, but now it seems that there is no need for that at all...!

WTF!
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Old 09-09-2015, 01:19 AM   #18
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Default Re: 12MHz clock generator for the Holtek HT6542b

I see you made to number 2 in the SuperPi 32M challenge.
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Old 09-09-2015, 01:54 PM   #19
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Default Re: 12MHz clock generator for the Holtek HT6542b

Well, I optimize my Windows and I should be even more competitive then with the P90. Fun stuff. Maybe I should do some voltmoding and extreme cooling...

Or at least figure out with WPCREDIT how to change TRP to 2 from 3... because that would be kick-a$$ then!
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