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From: 252u3130@fergvax.unl.edu (Phil Dietz)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Static vs. static column vs. dynamic vs. ???
Message-ID: <1990Nov08.222823.1925@hoss.unl.edu>
Date: 8 Nov 90 22:28:23 GMT
References: <15571@brahms.udel.edu>
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Organization: Comp Sci and Engr, Univ. of Nebr.
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In article <15571@brahms.udel.edu> don@brahms.udel.edu (Donald R Lloyd) writes:
>
>	I've been looking for information on the various type of RAM for a week
>or so, (more out of curiosity than out of any real need to know), and so
>far have found only what I already knew:
>
>	DRAM is relatively slow & has to be periodically refreshed
>	static RAM is fast & needs no refresh
>

I'm not too sure that TRUE statis rams are faster.  In my book Computer
Organization (Hamacher Vranesic Zaky ver 3 pg 322) it quotes
 
"MOS transistors are higher-impedence devices; they yield circuits that
have lower power dissipation.  Their disadvantage is their slower speed
of operation."

>	I also found brief mention of "pseudo-static RAM" (in Tannenbaum's
>"Stuctured Computer Organization", 3rd edition), which is basically
>dynamic RAM with some refresh circuitry on-chip (?).
>	Questions:
>		Why is DRAM slower than SRAM?  I can't see how having to refresh it
>		would cause any tremendous slowdown.
>
 
Well, everything takes time.  It may only take nanoseconds to refresh
the RAM, but it is ALWAYS refreshing the RAM.  The time slowly but
surely adds.....
 
Also looking at a DRAM schematic, I notice that the DRAM has a Timing
control segment that is connected to the Refresh Control and Refresh
counter modules....All this stuff to keep track of what SRAM already
does without.  I guess all this EXTRA stuff really burdens the speed...

>		What is static column RAM?  I've been told it's the same as static
>		RAM, but that doesn't seem right (otherwise the 3000 would be 
>        a good bit faster and a good bit more expensive).  Is it the 
>		equivalent of what Tannenbaum calls pseudo-static?
>
>		What about VRAM?  Somehow specially designed for video memory, or
>		just some marketer's way to make the static RAM on a video card
>		sound superior?
 
In Computer Organization it quotes:
 
"<About DRAM> The faster rate attainable in block transfers can be exploited in
specialized machines in which memory accesses follow regular patterns,
such as GRAPHICS TERMINALS.  This feature can also be benefitial in
general-purpose computers for the transfer of data blocks between the
main memory and a cache...."
 
>
>		While I'm at it, why are ROMs inherently so slow?
>
>		Why is there air?
>
>		How many licks does it take to get to the center of a Tootsie Pop?
 
One big one.   :)

>
>		Where's my free 68040 upgrade for the 3000 I just ordered?
>
>	Thanks for any info you can provide.
>
>
>-- 
>  Gibberish             Soon to be Amiga 3000 owner/fanatic! (I hope)
>  is spoken             Contact don@brahms.udel.edu for more information.
>    here.               DISCLAIMER:  It's all YOUR fault.

Phil Dietz

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