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Multibus address space
8/5/86

Multibus I/O Space:

I/O space is considered to be an 8-bit space for purposes of allocation,
but this is probably not necessary.  The current devices decode 12 or 16
bits, so it should be possible to use more than the first 256 locations.

Customers may use I/O ports 0xc0 .. 0xff.  LMI will attempt to keep these
free in future releases.

Multibus I/O space:
	0x2000..0x3f00	TITN
	0x40 .. 0x43	smd 2181
	0x60 .. 0x63	tapemaster
	0x80 .. 0x87	mti (systech serial mux)
	0xa0 .. 0xa7	excelan ethernet

Multibus Memory Space:

The system uses a 20-bit Multibus address space.  The devices listed in
the table are the only fixed addresses at present.  Multibus devices and
SDU programs that do DMA access to the NuBus must have additional
multibus space to use for the transactions that are mapped to the NuBus.

20-bit Multibus memory space:
	0x0-ffff	0 .. 63k	SDU RAM
	0x18000-18fff	96 .. 99k	SDU multibus => nubus map control registers
	0x1c000		112k		SDU registers (serial ports etc.)
	0x1e000-1ffff	120 .. 127k	SDU cmos ram
	x20000-23fff	128 .. 143k	Reliance serial I/O
	x2f8000		190k		Burr-brown debug master (second)
	x2fc000		191k		Burr-brown debug master (first)
	x30000-31fff	192 .. 199k	3com ethernet
	x38000-3ffff	224 .. 255k	CDC serial I/O
	x40000-xeffff	256 .. 960k	Dynamically allocated area
	xf0000-xfffff	960 .. 1023k	SDU ROM

The "dynamically allocated area" is the resource for the Boot software
and for the DMA transfers for normal operation of all the processors.
Space in this area is allocated from the bottom up; whatever is left is
available for user-defined Multibus operations and is allocated from the
top down.  This ensures that the user-defined area is at a fixed
location (the top end, at least) independent of the amount of the
available space.

To compute the available space, subtract the appropriate numbers shown
below from 700k.

Space required for all configurations:
	100k	SDU Boot (Newboot)
	140k	LAMBDA (each)
	70k	System V UNIX (each)
	50k	2.0 V7 UNIX (each)

Space taken by optional DMA devices:
	70k	Tapemaster 1/2" tape
	30k	Excelan Ethernet (each)
	4k	MTI serial I/O (each)
	??	CDC serial I/O
	??	Reliance serial I/O

For example, the following table shows the available space for some
configurations, not including any optional DMA devices.

Space available, not including optional DMA devices:
	460k	LAMBDA
	390k	LAMBDA-Plus (System V)
	320k	LAMBDA 2x2
	250k	2x2-Plus (System V)
	184k	LAMBDA 3x3

The "available space" may be reserved by the using the SDU Config
program "system maps" command.  Config warns if the reserved space is
close to the limit.  If too much space is reserved, the machine will fail
to boot or may crash after some time.

Note that the available space computed and printed by Config is for V7
UNIX, and so should be decreased by 20k for System V.

For nB bytes of user-defined space, the address range is:
	(#xF0000 - nB) .. #xEFFFF
So, for 64k, that is #xE0000 .. #xEFFFF.

=============================================

Multibus interrupts:

	0	3com Ethernet
	1	SDU IOMSG (software)
	2	Tapemaster 1/2" tape (unix)
	3	<free>
	4	SMD 2181 disk controller
	5	<free>
	6	MTI serial I/O
	7	SDU disk driver (software)