Newsgroups: comp.sys.amiga.advocacy
Subject: Re: 020 vs 030
From: lkoop@TIGGER.STCLOUD.MSUS.EDU (LaMonte Koop)
Date: 14 Aug 92 02:30:14 -0600
Reply-To: lkoop@TIGGER.STCLOUD.MSUS.EDU
Organization: St. Cloud State University, St. Cloud, MN

In article <AHANSFOR.92Aug13215914@starbird.wpi.edu>, ahansfor@starbird.wpi.edu (Andrew L. Hansford) writes:
>
>Why should C= put an 030 into baseline machines?  I agree that upper
>end and even middle end machines should have them (in case you want to
>run Unix or Enforcer, or Mungwall.)
>
>First, assume that on a base line machine you do not need an MMU.  Am
>I right in assuming that the current OS does not use it.  (the three
>things I mentioned above do right?)  An MMU is also handy for
>remapping the OS to 32 bit RAM.   Other that that???  Hey if an OS
>upgrade that uses the MMU is close (6 months) then go 030.
>
>If we don't use an MMU then how about the EC030. Where does the 030
>and EC030 give you an advantage over an 020 in speed if you don't use
>and MMU. 
>
>1. data cache (256 bytes)
>2. burst mode 
>3. synchronous termination (shorter memory access cycles on 32-bit accesses)
>        (correct me if I'm wrong on this one)

No, you are correct.  The last two items are related to each other (BURST mode
cycles on the 68030 require a meeting certain synchronous setup timings), but
these are the basic differences between the 68020 and 68030.  Incidentally,
not much use is made of synchronous bus cycles on the Amiga (aside from the
BURST mode issue), and unless a real change in basic design goals is made this
will probably not be much of an issue.

>Also the EC030 and 030 are available up to 50MHz as opposed to 33MHz.
>In addition, a system designed for an EC030 and a regular 030 could be
>almost the same.  So a machine with no mmu could be cheaper than a
>machine with mmu but the system busses could be virtually the same.
>(If the CPU were socketed you could even have something were you
>ploped in a 030 for an EC030.)
>Prices.  These were quotes from Motorola that I got today.
>Unfortunately these are small quantity quotes (hundreds of units) but
>the salesperson said the price should scale.
>
>020   $55
>EC030 $60
>030   $145
>EC040 $165
>
>I hope that C= would go with at least an EC030 given this information.
>Question to those who know, is there a reason to take the 020 over an
>EC030.
>

    Indeed.  The 68030 and 68EC030 are identical parts save for the fact that the
EC part has no working MMU.  I have not been real pleased with the use of
EC series parts thus far.  Their implementation is a bit problematic in some
circumstances.  It is a real idiotic pain to properly identify in software
the 68EC030 from the standard 68030, and this can cause some system level
software problems, especially should anything desire to use the 68030's MMU.
The 68EC040 is even worse in that you cannot do a test on the part for an
MMU in any case at all.  Doing so may result in the system going down, as
the MMU there may be 1.) non functional - no problem...or 2.) partially
functional, in which case everything goes south when it gets turned on.  The
EC parts were meant for just what their designation gives: Embedded Controller
applications.  However, in reality it seems economics rule that issue here.
All in all, the EC030 would not be as much of a problem as the EC040 should the
design question come to play though.

                  ----------------------------------------
            LaMonte Koop -- SCSU Electrical/Computer Engineering
 Internet: lkoop@tigger.stcloud.msus.edu -OR- f00012@kanga.stcloud.msus.edu
               "You mean you want MORE lights on this thing???"
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Newsgroups: comp.sys.amiga.advocacy