Checksum: 28997
Path: utzoo!utgpu!anakin
From: anakin@gpu.utcs.toronto.edu (Anakin Research)
Date: Wed, 23-Nov-88 10:49:10 EST
Message-ID: <1988Nov23.104910.15213@gpu.utcs.toronto.edu>
Organization: University of Toronto Computing Services
Newsgroups: comp.sys.amiga.tech
Subject: 32-bit LUCAS memory board
Reply-To: anakin@gpu.utcs.UUCP (Anakin Research)

 
	I have been very heartened by the responce to the LUCAS Project
68020/68881 accelerator board for the 1000. It seems that indeed there
are many 1000 owners out there who have spent considerable money on their
machine and peripherals, who cannot afford to upgrade to the 2000 with an
'020 board installed. It is nice to know there are still hackers out there
to whom the idea of populating their own bare boards is a viable alternative
to the higher priced spread. Let me say now that I have appreciated your 
comments on the LUCAS Project on the nets and in your letters, and that I will
try to keep the LUCAS Project alive.
	Now that about 2/3 of the initial run of 120 LUCAS Boards has been
shipped, (This means I'm out of debt for the board costs), it is time to get
the 32-bit wide memory board in the works. I should have a first crack proto-
type ready for debugging in about a week. I thought it would be a good idea
to get your ideas about its configuration and functionality. Any comments, 
design ideas, or critisisms would be welcome. I would enjoy a lively 
discussion and it can only improve the end product. Again, in the spirit of
the LUCAS Project, I will try and keep end user price to a minimum.
 
			Proposed Memory Design
        		~~~~~~~~~~~~~~~~~~~~~~
 
	I will be using 1 Meg. DRAMS in a 256K X 4 configuration. This will 
allow expansion in 1 Meg. increments as you can afford more memory. I plan
to have sockets for a maximum of 4 Meg. 
	I plan to use the National DRAM controller 8428D-70. This part though
a tad expensive $45.00 (U.S) will simplify the design and keep the chip
count down to a minimum. It also will allow me a quicker design path. (Free
time is becoming a precious commodity for me.) This controller will also 
do some memory interleaving and should provide the optimum memory access speed
	To auto-config or not to auto-config! It seems to me that there is a 
slightly messy way to auto-config the 32-bit wide memory. By cutting the 
config pin (12) on the exapansion connector, (it is just  shorted to ground)
and bringing a new config line from the memory board to pin 12, this would
allow the memory to be autoconfiged first in the chain. Alternatively, we could
not hack at the board but use some addmem like program to configure the memory.
I would like to hear any comments on which way would be most efficent form a
software point of view.
	Power considerations. I have been asked why on the LUCAS '020/881
board I provided so many 5 Volt pins on the 96 Pin DIN connector. It was
not to provide power for the memory board but to recieve power from it.
I plan to have a connector on the memory board which will accept the 
connector from the power supply which currently goes to the mother board, and 
then, of course, bus it from there to the mother board. This should allow easy 
installation, and as a side effect improve the noise floor on the LUCAS
board.
	I would like to move the kickstart area into this 32-bit wide path.
I must admit that I haven't given this enough thought and any ideas on how 
this would be accomplished would be appreciated. I can prevent assertion of
*AS (Address Strobe) in the kickstart range and simply have ROMS on the LUCAS 
memory board. This seems to me constitute a copywrite infringement. Anyone 
understands the legalese of this and who could hopefully suggest an honest 
workaround, please advise me.
        I understand that many of you would like to have an MMU. I don't have
the neccessary software smarts to make this compatable with the proposed
unix environment for the amiga and I think other problems may be there as 
well. I am certainly willing to discuss it. My fear is that this will
increase the cost of the board with perhaps little practical gain.
        
 
                                Brad Fowles
 
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