Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!think!snorkelwacker!mit-eddie!rutgers!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga
Subject: Re: A2630 questions (for Dave Haynie this time) [REPOST]
Keywords: A2630
Message-ID: <9696@cbmvax.commodore.com>
Date: 15 Feb 90 17:53:18 GMT
References: <1251@crash.cts.com> <9442@cbmvax.commodore.com> <1277@bmers58.UUCP> <1287@bmers58.UUCP>
Reply-To: daveh@cbmvax.cbm.commodore.com (Dave Haynie)
Organization: Commodore, West Chester, PA
Lines: 86

In article <1287@bmers58.UUCP> keithh@atreus.UUCP (Keith Hanlan) writes:
>I think this one disappeared somewhere...

>>All of this depends on where things are mapped.

>	Dave, I'm a little on the dense (in-experienced) side. Could you
>	elaborate this last bit for me please. 

>	o What is the difference between AddMemed memory and 
>	  Autoconfig memory to a DMA device?

Autoconfig memory is memory that supports the Amiga AUTOCONFIG(TM) protocols
and is automatically recognized and added by the Amiga's expansion.library.
AddMemed memory is manually added at a hardwared memory location, usually a
line somewhere in your Startup-Sequence if you have such memory.  By the
rules, any device in the $00200000-$009FFFFF range MUST be autoconfiguring,
and any device that doesn't autoconfigure MUST be located outside of that
range.  That puts extra 32 bit memory outside of the 68000's address space,
since there isn't any other space available to add-ons in the 68000 address
space.  So if you follow the rules, on A2500/xx and below, all autoconfigured
memory will be accessible by DMA device, no AddMemed memory will be.

>	o Is it possible to autoconfig only, say, 6MB of the 32bit RAM and
>	  let an additional device, such as a Bridgeboard or my 2058/2, 
>	  use the remaining 2MB of autoconfig space? Is this basically
>	  a question of whether or not the manufacturer provides enough
>	  flexibility through jumpers?

Autoconfiguration units come in power-of-two sizes.  If a 68030 board allowed
configuration of 4, 6, and 8 megs of memory, it would have to actually offer
two separate configuration units, since the 6 meg size is actually composed of
a 4 meg unit and a 2 meg unit.  ASDG's standard 16 bit Zorro II memory board
did this, but most don't.  The A2630 only have 4 megs of memory in 68000 space,
which may actually be set by jumper as either 2 or 4 megs.

>	o Is there a way to conditional autoconfig different cards
>	  depending on whether or not the machine is booted in 68000 mode?
>	  That is, say I have the following: A2630/8MB (eventually) and 
>	  A2058/4MB:
>	  1. In default 68030 mode, I want all the 32bit RAM to be autoconfig
>	  and the 16bit RAM to be AddMemed since you imply that the
>	  autoconfig RAM is faster for DMA. (right?)

Well, things work out the way you want them in 68030 mode.  You MUST 
autoconfigure any autoconfiguration unit, you can't simply addmem them.  And
it's the OS that does it; at least without going to a great deal of trouble,
you have little choice how cards get configured.  But with an A2630 system or
pretty much anything else that lives in the CPU slot, any autoconfiguration
unit there will show up before anything in the Zorro II bus.  So your 32 bit
memory will appear before any 16 bit memory available.  The only real question
would be if you had a mixture of 16 and 32 bit resources, and wanted a special
setup in 68000 mode.  For instance, you have 4 megs of 32 bit memory, an AT
bridgecard, and 4 megs of 16 bit memory.  If the 4 megs of 16 bit memory is
ahead of the bridge card on the bus, it'll get configured first and the bridge
card, no longer having any room, will be told to shut up.  So you'd have to
locate the Bridge Card before the extra 16 bit memory for things to work out
just great.  The 1.4 OS will be more robust in autoconfig slot allocation, but
I don't know if it has any plans to support this rather weird type of
situation.

>	  3. If I can't have (1), can I autoconfig the 4MB of 16bit and only
>	  4MB of the 32bit?

Well, on an A2630, only the 4 megs of on-board memory will autoconfigure; any
daughtercard memory will have to be added in via AddMem type utilities.

>>...Commodore also required a 2 megabyte option,
>>which does limit a number of the "tricks" you can play with the 68030 to
>>make things go a little faster.

>	Can you suggest why they imposed this constraint? 

I'm certain it was the cost.  While memory prices have fallen dramatically over
the past year, you have to realize that the A2630 was basically done a year ago
this month.  At the time I was designing it, 2 megs of DRAM was over 1/2 the
cost of the card.  Given infinite time I probably could have done something 
more clever, but the A3000 was already biting at out heels, so the A2630 was
done as-is for several reasons.  I still today think it's a good design, it 
just might have been a tad faster had constraints been different.

>Keith Hanlan

-- 
Dave Haynie Commodore-Amiga (Systems Engineering) "The Crew That Never Rests"
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                    Too much of everything is just enough