RE: [N8VEM-S100:3477] ALTAIR/IMSAI 8080 CPU replacement board

John,

I'm going to need to learn more about this Master/Slave business. I'm adding something to the board I call Master/Slave, but it might not be what you are thinking about. The idea was to be able to use the Memory and I/O on this card but from another CPU on the bus. In this configuration, the 8080 cpu doesn't need to be installed and the bidirectional drivers for the S-100 bus are all reversed by the jumpers.

Now please describe your Master/Slave capability?

Regards,
Josh Bensadon

From: mon...@vitasoft.org
To: n8vem...@googlegroups.com
Subject: RE: [N8VEM-S100:3477] ALTAIR/IMSAI 8080 CPU replacement board
Date: Sat, 3 May 2014 09:28:43 -0700

Josh, if you can try and insert the master/slave capability. A few flip flops is all it takes, makes it very useful to work with other CPU’s (including a Z80).

John

From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of Crusty OMO
Sent: Saturday, May 3, 2014 7:32 AM
To: n8vem...@googlegroups.com
Subject: RE: [N8VEM-S100:3474] ALTAIR/IMSAI 8080 CPU replacement board

Fabio,

Yes, once I have all the bugs worked out and features working, I intend to re-enter the schematic into KiCad and build a board. The present features of the board were actually arrived to by a general consensus and discussion from this group.

The features thus far are:
-onboard RAM/ROM with option to map out some of it to S-100 space (in 8K chunks).
-Shadow ROM, that is, the EPROM occupies some space in the memory map until it's disabled, at which point, RAM at the same location will be used.
-Two UARTS, 8250 type
-SD Card interface using SPI
-Limited parallel I/O (6 outputs, 8 inputs). I'm using 2 outputs to control shadow ROM and SD Card
-Either run as the 8080A CPU or run as a slave board to an external CPU, thus making it a Memory and I/O card by reversing direction of all the buffer chips.
-Both ALTAIR and IMSAI FP connectors.

I am intending to take this project to the point where it's a board and write some BIOS so CP/M can be booted up from a Disk Image file on the SD Card. This later part may take a while as I have other commitments to get an exhibit booth ready for VCF MW, this coming September.

Cheers,
Josh

Date: Sat, 3 May 2014 16:11:00 +0200
From: hkzl...@gmail.com
To: n8vem...@googlegroups.com
Subject: Re: [N8VEM-S100:3472] ALTAIR/IMSAI 8080 CPU replacement board

Hmmm, I can't offer advice but I'd like to know if you plan to ever do a production run of this once it works.
Maybe it's a bit early to ask, but I do like the idea (and have a few spare 8080 around :-D

Oh, and that 8080 is lovable BTW!
Fabio

On 03/05/14 16:05, Crusty OMO wrote:

Hi Group,

Well, now that these "Sea of PTH" buffered prototype boards are built, my first project on one of them is the 8080A CPU replacement board I started talking about back in November.

I have the prototype built (for the most part). I plugged it in, but it's not working... yet.
But at least I'm at the trouble shooting stage.
Photo's below.

Regards,
Josh Bensadon

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