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- Newsgroups: sci.electronics
- Path: sparky!uunet!caen!umeecs!johnwitt
- From: johnwitt@cdrom.engin.umich.edu (John P Wittkoski )
- Subject: Minimum speed on processors
- Message-ID: <1992Aug27.135703.26001@zip.eecs.umich.edu>
- Originator: johnwitt@cdrom.engin.umich.edu
- Sender: news@zip.eecs.umich.edu (Mr. News)
- Organization: University of Michigan Engineering, Ann Arbor
- Date: Thu, 27 Aug 1992 13:57:03 GMT
- Lines: 31
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-
- For a 33MHz 68030, there is a minimum clock speed listed for it in
- the databooks. I think it's somewhere around 25Mhz for a 33MHz version, but I
- don't have my databook handy.
-
- My question is: why is there a minimum?
- One possibility I have heard is that the on-chip registers and/or cache
- are dynamic in nature, and since the chip is geared for 33MHz, it divides
- this down to whatever rate is needed for the refresh circuitry. Therefore,
- if you go below the minimum, the refresh rate slows to below the minimum
- needed for the refresh.
-
- Now, is there someone out there who knows about this? I'm interested
- specifically in the 68xxx CPUs, but any general info would be helpful.
- For example:
- 1. Is the guess I made above accurate, or is there some other reason?
- 2. If the reason above is correct, does it apply to the registers, the
- cache, or both (or neither?)
- 3. If it's just a testing parameter, how far could I crank the clock speed
- down? 20Mhz? 16,8,2,1???
-
- Just curious.
- Reply by newsgroup or email, whichever is easiest for you.
-
- --John Wittkoski
- University of Michigan
- johnwitt@engin.umich.edu
-
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