[comp.sys.nsc.32k] Next revision of the PC532

rhyde@ucrmath.ucr.edu (randy hyde) (04/06/91)

George, if you ever make any changes to the PC532 PCB, I have a small
suggestion:  It appears like "B" port on the 6250 chip is unused.  I suggest
that you wire up a set of 8 dip switches to this thing.  That would allow
owners to select certain cold boot options (e.g., system SCSI port address,
initial Baud rate, whether to boot from disk  or enter the monitor, whether
or not an FPU is installed [shades of IBM!], etc.).

Yeah, I'm already warming up the soldering iron and using some of those
spare sets of holes on the board.  Having a standard, supported, set of
dip switches would be nice, though.

m937290@usna.NAVY.MIL (Midn. Norman R. Solis) (04/11/91)

Where can I get more information about this PC532?  I've asked before but
haven't received any responses.  How much does it cost to build?

-Rich Solis

m937290@n1.usna.navy.mil
-- 
N Richard Solis		m937290@n1.usna.navy.mil		GO NAVY!
USNA 33rd Company	m937290@midn.ecs.usna.navy.mil		BEAT ARMY!
Annapolis, MD 21412
(301) 267-5001		United States Naval Academy - Class of 1993

george@wombat.UUCP (George Scolaro) (04/15/91)

In article <303@usna.NAVY.MIL> m937290@usna.NAVY.MIL (Midn. Norman R. Solis) writes:
>
>Where can I get more information about this PC532?  I've asked before but
>haven't received any responses.  How much does it cost to build?
 ^^^^
	Not while I've been reading the net - must have been on holidays...

Anyhow, in terms of cost to build, any of the people that have built one up
should be able to tell you. Come on folks, one volunteer for the cost...

FOR THOSE THAT HAVEN'T NOTICED MY PREVIOUS POSTING, A NEW PC532 PCB RUN IS
PLANNED. I am getting a count for boards to run, if you want one or more
please email me your name, address, quantity requested to gs@wombat.bungi.com
and I'll tally the score. I have spoken to the pcb house and a run of 10
might not be outrageous in price, so far I have around 6 boards requested.

With respect to what it is:

-----

The PC532 is a homebrew NS32532 based motherboard. It was designed during a
2 year period, evolving from a PC/AT wirewrap prototype to a baby PC/AT
sized motherboard. The complete schematics (gerber files if required) and
PLD equations for the design are freely available, as is all the source code
that has currently been written. The initial 'production' run of PCBs came
to 65, second run of 37, and a third run of 20. With National's generous
support we were able to supply 50 NS32532/NS32381/NS32202 chipsets with the
first 50 PCB orders. The initial 65 boards were kitted with the more hard to
get components and connectors. Kits with NS chipset were $450 and kits
without were $400.

The main justification for the PC532 and its brethren is to foster free
hardware design and to provide a platform for development of freely available
software. With the evolution of the PC/XT/AT computers, hardware hacking has
been on the decline. In addition, the increasing complexity of new
generation CPUs has also made it difficult for the home based tinkerer to
venture into the design of a computer system. The PC532 attempts to provide
the base from which new designs can gain leverage. In the long term the PC532
will likely become an adapter for a higher performance CPU.

Over the past few years there has much discussion in some of the news groups
about designing the ultimate homebrew computer, but this rarely ever
concluded. The reality is that few people actually have enough spare time to
design and carry through to completion anything other than the simplest of
projects. The PC532 was architected by two people, one hardware oriented the
other software oriented. Even with only two people, many discussions
(battles) occurred (were fought) prior to the final specification and design.

The current PC532 mailing list has a mixture of people with hardware and
software backgrounds. It currently appears that the software people
outnumber the hardware people. This is probably a good thing, since it
ensures that any hardware that is produced will have good software support,
based on the infinite number of monkeys principle (or less than infinite if
some aren't monkeys :-) ).

Following is a partial excerpt from the PC532 Functional Description
document:

The PC532 is a motherboard which mechanically fits into a PC/AT case. The
mounting holes and power supply connections are arranged accordingly. The
PC532 has 4 PC/XT slots which are mechanically placed to enable a PC/AT
case to be used, though electrically they support the SCSI protocol.

The printed circuit board (PCB) has 6 layers, comprising of two active outer
layers, 2 active inner layers, 1 power layer and 1 ground layer.

The PC532 board has the following features:

1 x NS32532 25 Mhz CPU

1 x NS32381 25 Mhz FPU

1 x NS32202 10 Mhz ICU

1 x DP8490 SCSI device that manages a 62 pin XT mechanically compatible 4
slot multi-master bus. This bus can run to at least 3.8 megabytes per second.
Multi-master is supported by the DP8490 SCSI device.

1 x AIC6250 SCSI device, connects to a 50 pin SCSI header. This device
is intended to connect to hard disk and mag tape media. The AIC6250 supports
async and sync SCSI. The interface supports data transfer rates over 4
megabytes per second.

4 x SCN2681 DUARTs. This gives the PC532 8 serial channels, which are all
individually connected to interrupt inputs on the ICU. Each DUART generates
an INT and in addition a wire or-ed RX ready channel A/channel B.

1 x 27256 EPROM (200 ns). This EPROM contains any necessary boot firmware.
It is intended that a Dallas Semiconductor (or compatible) clock chip/socket
be used under the EPROM to give the PC532 a battery backed real time clock.

4/8 megabytes (1 megabit x 8/9 80ns SIMMs) or 16/32 megabytes (4 megabit x
8/9 80 ns SIMMs). Page mode dram devices must be used and the design utilizes
the page mode access to achieve 0 wait state read (1st access), 0 wait state
write, 1 wait state for the rest of a read burst if in page. If not in page
a penalty of 4 wait states for reads and 3 wait states for writes occurs. The
result is a peak 50 megabyte/second memory interface (while bursting in
page).

The board currently runs a modified version of MON16 which enables a 32000
host system to download code, set break points, source level debug etc.
Bruce Culbertson has also ported his monitor to the PC532 and Minix. Many
other people are working on different flavours of OSes etc.

Compute performance is roughly 10 X a 32016 based system (ICM3216). I/O
performance should be considerably faster.

Total of 50 devices, including CPU etc, but excluding the DRAM SIMMs. There
are 2 D-speed PAL devices and 3 B-speed PAL/GAL devices on the board. All
glue logic, buffers and latches are either 74AS or 74ALS technology.

The PCB is 6 layers, 13.5 inch x 8 inch baby AT form factor. It connects to a
standard AT power supply (draws 2.6 Amps typical), has holes to mount in an
AT chassis, has 4 XT (mechanical only) slots that will accept XT or AT
wirewrap prototype cards (power pins are XT compatible).
------

P.S. I designed the hardware (with architectural help from Dave Rand), and
routed the PCB.

best regards,
-- 
George Scolaro
george@wombat.bungi.com                [37 20 51 N / 122 03 07 W]