Path: utzoo!attcan!uunet!fernwood!apple!usc!ucsd!nosc!crash!pro-party.cts.com!seanc
From: seanc@pro-party.cts.com (Sean Cunningham)
Newsgroups: comp.sys.mac.misc
Subject: Re: Surely a IIFX blows an Amiga 3000 away, right?
Message-ID: <5205@crash.cts.com>
Date: 23 Oct 90 05:16:09 GMT
Sender: root@crash.cts.com
Lines: 36

In-Reply-To: message from es1@cunixb.cc.columbia.edu

 
Something I'd also like to add to what you posted, regarding the buss of the
A3000.
 
Zorro ]I[, unlike NuBus (which is the same from the Mac ][ to the ][fx) is an
asynchronous design, meaning the 68030 doesn't have to sync up with the speed
of the buss to talk to it.  On a stock A3000, this isn't a huge hassle because
both the CPU and buss are at 25MHz.  By contrast, the ][fx is running at
40Mhz, but NuBus is at 10MHz.  What this amounts to is that the ][fx becomes a
10Mhz Mac anytime it wants to talk to the NuBus, and a 20MHz Mac anytime it
wants to talk to the I/O buss. 
 
Another point to make is that Zorro]I[ has access to memory on the A3000's
mother board at full system speed, or 20MB/sec in standard mode, or somewhere
between 30-40MB/sec in Multiple File Transfer mode.  Although NuBus has a
block-transfer mode of 37.5MB/sec, this isn't supported beyond the NuBus. 
Even on the Mac ][fx, access from a peripheral card on the NuBus (ie:
videocard) when talking to main-memory slows to 4-5MB/sec.
 
I'm sure you Mac guys are getting a real kick out of this...so I guess I'll
end it here.  
 
Sean

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