[N8VEM: 18972] ECB bus expansion to 32-bit addressing

Discussion:

John Coffman

2014-11-19 23:33:48 UTC

To All,

The address path on the N8VEM ECB bus was expanded about three years ago
to 24-bits, and the Z180 Mark IV (CPU) board is capable of using memory
addressing expanded to 24-bits. The board works with the ECB 4MEM
expanded memory board, although that board, designed for the SBC-188,
uses only 20 address lines (8086/88 & 80186/188).

Thoughts about CPU boards in the 68000 family, lead to thoughts of
actually using the 16-bit data path which was defined 3 years ago for
the N8VEM bus. However, expansion of the address bus should also be
considered.

Hence, I am proposing:

1. Expansion of the address bus to 28-bits using pins: B-2, B-3,
B-4, & B-5. [A24..A27]
2. Continuing the expansion to 30-bits using pins: B-30, & B-31.
[A28..A29]

The above proposed pins to be used are as yet unassigned on the 96-pin
connector.

3. Expansion to 32-bits would use open pin A-16 for bit A30. Pin
C-15 is currently unused on the N8VEM bus, but somewhere there is
documentation that some manufacturer used it for a -12/15v power supply
pin in the past. Since this has been a deprecated pin on the N8VEM bus
for many years, I propose to re-assign it as address A31.

Should all of the above be adopted, there remain 3 deprecated pins on
the N8VEM ECB connector:

A-13 -- reserved for +12v, but not currently used for that purpose
A-15 -- reserved for -12v, but not currently used for that purpose
A-19 -- reserved for +12/15v, but not currently used for that purpose

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

Attached: ECB-05.jpg (current bus), ECB-06.jpg (proposed expansion)

--John

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yoda

2014-11-20 01:50:15 UTC

Permalink

Hi John

I assume the proposal is to use this with the wider (6U size?) boards as
well? Otherwise the smaller form factor boards would be hard pressed to be
able to extend to these capacities. A 68000 with the PLCC version would
fit but if you further without more board real estate it would be difficult
to get enough support logic on the small form factor boards.

The proposal looks reasonable to me.

Dave

Post by John Coffman
To All,
The address path on the N8VEM ECB bus was expanded about three years ago
to 24-bits, and the Z180 Mark IV (CPU) board is capable of using memory
addressing expanded to 24-bits. The board works with the ECB 4MEM
expanded memory board, although that board, designed for the SBC-188,
uses only 20 address lines (8086/88 & 80186/188).
Thoughts about CPU boards in the 68000 family, lead to thoughts of
actually using the 16-bit data path which was defined 3 years ago for
the N8VEM bus. However, expansion of the address bus should also be
considered.
1. Expansion of the address bus to 28-bits using pins: B-2, B-3,
B-4, & B-5. [A24..A27]
2. Continuing the expansion to 30-bits using pins: B-30, & B-31.
[A28..A29]
The above proposed pins to be used are as yet unassigned on the 96-pin
connector.
3. Expansion to 32-bits would use open pin A-16 for bit A30. Pin
C-15 is currently unused on the N8VEM bus, but somewhere there is
documentation that some manufacturer used it for a -12/15v power supply
pin in the past. Since this has been a deprecated pin on the N8VEM bus
for many years, I propose to re-assign it as address A31.
Should all of the above be adopted, there remain 3 deprecated pins on
A-13 -- reserved for +12v, but not currently used for that purpose
A-15 -- reserved for -12v, but not currently used for that purpose
A-19 -- reserved for +12/15v, but not currently used for that purpose
===========================================
Attached: ECB-05.jpg (current bus), ECB-06.jpg (proposed expansion)
--John

John Coffman

2014-11-20 14:00:45 UTC

Permalink

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Dave,<br>
<br>
Yes, the proposed bus configuration would be a very good idea for
the wide Eurocard (160mm x 233mm) boards as well.  (AFAIK, the 6U
6x0x board is the only one.)<br>
<br>
I've been mulling over so many different approaches to putting a
680x0 on a board, that the wider format is under consideration.  My
original roadmap to a 68000 board remains:  existing Mini-68K (68008
cpu) + MF/PIC for I/O.  Add a 16-bit memory board, and then an
upgrade to a 680x0 CPU on a 24-31 bit address bus and 16-bit data
path becomes possible.<br>
<br>
--John<br>
<br>
<br>
<br>
On 11/19/2014 05:50 PM, yoda wrote:
<blockquote
cite="mid:3128f9be-44df-4c24-86ca-***@googlegroups.com"
type="cite">
<div dir="ltr">Hi John
<div><br>
</div>
<div>I assume the proposal is to use this with the wider (6U
size?) boards as well?  Otherwise the smaller form factor
boards would be hard pressed to be able to extend to these
capacities.  A 68000 with the PLCC version would fit but if
you further without more board real estate it would be
difficult to get enough support logic on the small form factor
boards.</div>
<div><br>
</div>
<div>The proposal looks reasonable to me.</div>
<div><br>
</div>
<div>Dave</div>
<div><br>
</div>
<div><br>
On Wednesday, November 19, 2014 5:35:23 PM UTC-6, John Coffman
wrote:
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
0.8ex; border-left: 1px solid rgb(204, 204, 204);
padding-left: 1ex;">To All,
<br>
<br>
The address path on the N8VEM ECB bus was expanded about
three years ago
<br>
to 24-bits, and the Z180 Mark IV (CPU) board is capable of
using memory
<br>
addressing expanded to 24-bits.  The board works with the
ECB 4MEM
<br>
expanded memory board, although that board, designed for the
SBC-188,
<br>
uses only 20 address lines (8086/88 & 80186/188).
<br>
<br>
Thoughts about CPU boards in the 68000 family, lead to
thoughts of
<br>
actually using the 16-bit data path which was defined 3
years ago for
<br>
the N8VEM bus.  However, expansion of the address bus should
also be
<br>
considered.
<br>
<br>
Hence, I am proposing:
<br>
<br>
    1.  Expansion of the address bus to 28-bits using pins:
 B-2, B-3,
<br>
B-4, & B-5.  [A24..A27]
<br>
    2.  Continuing the expansion to 30-bits using pins:
 B-30, & B-31. <br>
[A28..A29]
<br>
<br>
The above proposed pins to be used are as yet unassigned on
the 96-pin
<br>
connector.
<br>
<br>
    3.  Expansion to 32-bits would use open pin A-16 for bit
A30.  Pin
<br>
C-15 is currently unused on the N8VEM bus, but somewhere
there is
<br>
documentation that some manufacturer used it for a -12/15v
power supply
<br>
pin in the past.  Since this has been a deprecated pin on
the N8VEM bus
<br>
for many years, I propose to re-assign it as address A31.
<br>
<br>
Should all of the above be adopted, there remain 3
deprecated pins on
<br>
the N8VEM ECB connector:
<br>
<br>
    A-13 -- reserved for +12v, but not currently used for
that purpose
<br>
    A-15 -- reserved for -12v, but not currently used for
that purpose
<br>
    A-19 -- reserved for +12/15v, but not currently used for
that purpose
<br>
<br>
==============================<wbr>=============
<br>
<br>
Attached:  ECB-05.jpg  (current bus), ECB-06.jpg (proposed
expansion)
<br>
<br>
--John
<br>
<br>
<br>
<br>
<br>
</blockquote>
</div>
</div>
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yoda

2014-11-20 15:08:10 UTC

Permalink

John,

Seems reasonable. We will be limited to up to 68030 without some more
magic because 040 and beyond don't really support dynamic bus sizing and
the proposed extension doesn't support 32 bit data bus. I think we are
going to have to come to grips as how we are going to address larger
memories. Static memories are not going to take us far enough. Either
going to have to go to SMT or come up with a dynamic memory controller.

BTW - will be happy to work with you on further 680x0 designs as this is my
favorite architecture.

Dave

Dave,
Yes, the proposed bus configuration would be a very good idea for the wide
Eurocard (160mm x 233mm) boards as well. (AFAIK, the 6U 6x0x board is the
only one.)
I've been mulling over so many different approaches to putting a 680x0 on
a board, that the wider format is under consideration. My original roadmap
to a 68000 board remains: existing Mini-68K (68008 cpu) + MF/PIC for I/O.
Add a 16-bit memory board, and then an upgrade to a 680x0 CPU on a 24-31
bit address bus and 16-bit data path becomes possible.
--John
Hi John
I assume the proposal is to use this with the wider (6U size?) boards as
well? Otherwise the smaller form factor boards would be hard pressed to be
able to extend to these capacities. A 68000 with the PLCC version would
fit but if you further without more board real estate it would be difficult
to get enough support logic on the small form factor boards.
The proposal looks reasonable to me.
Dave

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Kip Koon

2014-11-20 09:10:07 UTC

Permalink

Hi John!
Sounds like a great idea to me. If we are going to be making/using ECB SBC PCBs with processors that have a 32-bit address bus on the ECB Backplanes, for example like the Motorola MC68030, as well as CPUs from other manufacturers with 32-bit address busses then it becomes very clear to me that this change in the ECB pin out definition is necessary and required in my opinion. Great idea John. You have my vote.

Kip Koon
***@sc.rr.com
http://www.cocopedia.com/wiki/index.php/Kip_Koon

-----Original Message-----
From: ***@googlegroups.com [mailto:***@googlegroups.com] On Behalf Of John Coffman
Sent: Wednesday, November 19, 2014 6:34 PM
To: N8VEM
Cc: Sergey Kiselev; Wolfgang Kabatzke
Subject: [N8VEM: 18972] ECB bus expansion to 32-bit addressing

To All,

The address path on the N8VEM ECB bus was expanded about three years ago to 24-bits, and the Z180 Mark IV (CPU) board is capable of using memory addressing expanded to 24-bits. The board works with the ECB 4MEM expanded memory board, although that board, designed for the SBC-188, uses only 20 address lines (8086/88 & 80186/188).

Thoughts about CPU boards in the 68000 family, lead to thoughts of actually using the 16-bit data path which was defined 3 years ago for the N8VEM bus. However, expansion of the address bus should also be considered.

Hence, I am proposing:

1. Expansion of the address bus to 28-bits using pins: B-2, B-3, B-4, & B-5. [A24..A27]
2. Continuing the expansion to 30-bits using pins: B-30, & B-31.
[A28..A29]

The above proposed pins to be used are as yet unassigned on the 96-pin connector.

3. Expansion to 32-bits would use open pin A-16 for bit A30. Pin
C-15 is currently unused on the N8VEM bus, but somewhere there is documentation that some manufacturer used it for a -12/15v power supply pin in the past. Since this has been a deprecated pin on the N8VEM bus for many years, I propose to re-assign it as address A31.

Should all of the above be adopted, there remain 3 deprecated pins on the N8VEM ECB connector:

A-13 -- reserved for +12v, but not currently used for that purpose
A-15 -- reserved for -12v, but not currently used for that purpose
A-19 -- reserved for +12/15v, but not currently used for that purpose

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

Attached: ECB-05.jpg (current bus), ECB-06.jpg (proposed expansion)

--John

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Borut

2014-11-30 10:29:47 UTC

Permalink

Hi John,

I think it would be better to expand to 32 bits similar to VME bus.
There are two connectors, P1 and P2.
P1 carries all control signals, addresses A0-A23 and data D0-D15.
P2 carries addresses A24-A31 and data D16-D31.
I don't know for any mainstream cpu supporting 32 bit address and only 16
bit data.
Cramming additional addresses into one ECB connector would just create
another bottleneck
with data lines.
Also pcbs for 32 bit cpus would be better off in 6U format, similar to
6x0x.

This was also the approach used by NDR Klein computers when expanded with
68020:
http://schuetz.thtec.org/DrCrazy/www.drcrazy.de/nkc/index.html

VME supports systems using only P1 bus, even with 32 bit systems, where
VME space is a 16MB window in 4Gb address space.
Just to be in the clear, i am not advocating all the complexities of VME
bus.

Regarding the glue logic, i don't know about Xilinx devices, but i like
Altera EPM7128SLC84 which comes in 84 pin plcc and is in system programmable
with a 10$ USB blaster.

lp,
Bo/