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Mark 8 variant

Dwight Elvey

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As follow up to earlier questions, the 4702A and 8702A were the MCS-4 and MCS-8 equivalent numbers for the 1702A. Electrically they are identical.

Martin Eberhard's ME 1702A programmer is excellent and works very nicely.

Another alternative which is sleek (but much tougher to construct) is Matthew Millman's 1702A Arduino Shield. Construction is not for the faint-of-heart but it's amazing to have a 1702A programmer that is not much larger than an Altoid tin! http://tech.mattmillman.com/projects/a-compact-programmer-for-1702a-eproms/

- Gary

As I recall, there were differences in things like the tolerance of the voltages and currents they would operate over but in a generic sense they were the same.
I've been meaning to setup a threshold adjustable reader my self. I have a EPROM that has serious bit rot but I'd like to get the data from or at lest what is left. It contains the fourth EPROM data of the 4004 assembler, running on a 4004, that Tom Pittman wrote for Intel. ( he also wrote the 6502 tiny basic ).
PMOS are suppose to be hard pull up and soft pull down. Kind of different than ttl.
Dwight
 

daver2

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Roland,

So, I spent the afternoon reading up on the MARK-8 and most of the information relating to what you have is on here https://bytecollector.com/m8_docs.htm - especially the key information stored in the file dg_packet.pdf (https://bytecollector.com/archive/mark_8/My_Mark-8_Info/DigitalGroupPacket/dg_packet.pdf) which unlocked the Octal keyboard, VDU etc.

They describe a ROM board for the initial cassette load - but it seems to be slightly different to the one you have (e.g. it doesn't use a 1702A - or equivalent - device).

Incidentally, you should be able to use your front panel controls (the octal keyboard) to EXAMINE what is in the EPROM. You shouldn't need to remove it and place it in an EPROM programmer/reader...

From the information I have read, this EPROM should start at OCTAL address 17300?

I also think I have spotted an 'error' with the address decoding (the 7430) associated with the EPROM. There appears to be a pin floating on it. It will float high - so this will be correct. However, with it floating, the machine will be susceptible to RFI...

I also don't get the same amount of RAM that you do. 2102 RAM devices are 1Kbit each. 16 devices per board = 2KBytes. 4 memory boards is therefore 8KBytes. The 1702 EPROM adds a further 256 Bytes...

I will also bring to your attention (if you don't know already) that the dg_packet.pdf file contains some test programs (including a memory test) starting on page IV-1.

I would be interested to see how close your EPROM contents are to what is described in the dg_packet.pdf file.

However, there is something not quite right with the address decoding somewhere for the EPROM - especially if you have 8KBytes of RAM in the machine...

Let me work on this - and read a bit further...

Dave
 

daver2

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Looking at the hand-drawn 0-7 octal keyboard back in the posts that DOESN'T look like the one in the dg_packet at all.

I would be interested in seeing what other "hand-drawn" schematics you have...

The keyboard looks like a 7 bit + strobe ASCII keyboard from what I have read.

Dave
 

Roland Huisman

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Quite a list of replies :)

Roland,

So, I spent the afternoon reading up on the MARK-8 and most of the information relating to what you have is on here https://bytecollector.com/m8_docs.htm - especially the key information stored in the file dg_packet.pdf which unlocked the Octal keyboard, VDU etc.

They describe a ROM board for the initial cassette load - but it seems to be slightly different to the one you have (e.g. it doesn't use a 1702A - or equivalent - device). Incidentally, you should be able to use your front panel controls (the octal keyboard) to EXAMINE what is in the EPROM. You shouldn't need to remove it and place it in an EPROM programmer/reader... From the information I have read, this EPROM should start at OCTAL address 17300?

Dave, thanks a lot for finding this stuff! I think I will put a 1702A with known data
into the machine. Then I can check if the ROM is at that address. The reason that I removed
the ROM is because the system was in unknown state at that time. I didn't want to
damage the ROM because the machine wasn't turned on for many years.
You never know with a power failure.


I also don't get the same amount of RAM that you do. 2102 RAM devices are 1Kbit each. 16 devices per board = 2KBytes. 4 memory boards is therefore 8KBytes.

Well, things might not be what they look like at first sight... Check this picture. Maybe you see what I mean :D
http://technischmuseum.nl/devices/Mark 8/Mark 8 10.JPG

I would be interested to see how close your EPROM contents are to what is described in the dg_packet.pdf file.

Me too! I'm pretty sure they didn't develop the code by them self. But it can be modified off course.

I'd say, that is the nicest functioning front panel for an 8008 I've ever seen, although the MIKE series 8008's from Martin Research (see Byte magazine #1, first ad page) come close. BTW I worked in the 80's for the successor to Martin Research, Qwint Systems, run by the Martin Research founders.

Yes and it works great too. That Mike is also a very nice machine :)
 
Last edited:

daver2

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>>> Well, things might not be what they look like at first sight... Check this picture. Maybe you see what I mean :).

Yep, it's amazing what a bit of 'perspective' brings to the proceedings!

Double stacked RAM on 3 out of the 4 cards with the /CS pin bent out. I remember this trick well :)!

Yep, I now get 14KB RAM like you! + 256 Bytes for the EPROM.

The VDU appears as an I/O port only (not memory mapped) according to what I have read.

That octal keyboard has me intrigued though! The original used the keys '0' to '7' to indicate the 'bit position' that required a '1' to be set. There was then a 'clear all' key to clear the S/R latches. This circuitry appears to be wired to behave as a true OCTAL digit rather than a 'bit position'.

Dave
 

Roland Huisman

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So I found the Mark 8 binders. There is one binder labelled 8008 Basic.
In that binder there is a book Scelbal. (I found that book online at scelbi.com
But the page order of that online version is messed up :( )

There are a few extra pages with hand written 'John Griffin' on it.

But between page 12-1 and 12-2 were these listings.

Mark 8 023.jpg Mark 8 024.jpg Mark 8 025.jpg Mark 8 026.jpg Mark 8 027.jpg

I have other binders too. One of them seems to have a mix of the Mark 8 and
some info for their newer system. The Altair... So stuff to figure out...

I would love to have that Scelbal on tape. I guess this should be possible to find?
The only thing that worries me is that Scelbal might need to be modified to run on this system?

Regards, Roland
 

Roland Huisman

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Well there is a huge amount of Digital Group documents. And guess what, the
documents Dave revered to are with the system. Even the papers to design the
boards are there. These drawings are for this TV board.

Mark 8 028.jpg Mark 8 028a.jpg

This is for the cassette interface board.
But while the DG group drawing is used as a reference, they used a XR210 chip on the board.
Mark 8 029.jpg

And the original documents of the memory boards are with the system.
And so are the documents with modifications.

Mark 8 037.jpg Mark 8 038.jpg Mark 8 038a.jpg

It seems the IO expansion with a lot of 7401 chips is also designed by the Digital Group.

So that leaves only some questions about the octal keyboard, the ASCII keyboard and the EPROM addressing.

I'm happy that they did a good job on documenting such a complex machine.
I even found the drawings of the case! I should scan all that stuff...
 

mwillegal

Experienced Member
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May 27, 2008
Messages
233
http://www.willegal.net/scelbi/scelbal.htm


Are you looking for SCELBAL on paper tape or cassette tape? Most original owners of 8008 systems bought the book and typed it in, sales of paper tape were very few.

I have made SCELBI audio tape compatible audio files using my 8008/SCELBI emulator and can load SCELBAL into SCELBI 8B and 8H systems with actual cassette tape drives.

Almost all 8008 software needs to be ported to specific system depending upon the actual I/O interfaces.

regards
Mike Willegal

So I found the Mark 8 binders. There is one binder labelled 8008 Basic.
In that binder there is a book Scelbal. (I found that book online at scelbi.com
But the page order of that online version is messed up :( )

There are a few extra pages with hand written 'John Griffin' on it.

But between page 12-1 and 12-2 were these listings.

View attachment 60919 View attachment 60920 View attachment 60921 View attachment 60922 View attachment 60923

I have other binders too. One of them seems to have a mix of the Mark 8 and
some info for their newer system. The Altair... So stuff to figure out...

I would love to have that Scelbal on tape. I guess this should be possible to find?
The only thing that worries me is that Scelbal might need to be modified to run on this system?

Regards, Roland
 

Roland Huisman

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Are you looking for SCELBAL on paper tape or cassette tape? Most original owners of 8008 systems bought the book and typed it in, sales of paper tape were very few.
I have made SCELBI audio tape compatible audio files using my 8008/SCELBI emulator and can load SCELBAL into SCELBI 8B and 8H systems with actual cassette tape drives.
Almost all 8008 software needs to be ported to specific system depending upon the actual I/O interfaces.

Hi Mike,

Thanks! I'm not sure for what I'm looking for... I'm not familiar with the software at all...
I have seen some handwriting in manuals and modified loaders. But I don't know the
background of them. And I'm not sure if these are still valid for the machine.
Because they developed the machine over time...

So when I have the machine running I should start with the paper tape version?

Regards, Roland
 

jdreesen

Experienced Member
Joined
Jul 5, 2012
Messages
325
Location
Switzerland
Roland and others,

do download and install my i8008 system emulator : ( Windows program, but does run under Wine)

ftp://ftp.dreesen.ch/Scelbal/I8008.zip

Once installed you will be able to run Scelbal

In the install directory you will find the commented source code of Scelbal, a small user guide "scelbal.txt" and C-sourcecode for the emulator and the 8008 asembler.

Roland, all you need to do is to punch the Scelbal binary sc.bin to papertape, and load that into your machine.


Below some notes I made about Scelbal :

- Scelbal uses ASCII characters with bit 7 set. ( Mandatory !)
- It is also mandatory to use "SCR" before entering a program.

==========================
== SCELBAL ==
==========================

--executive commands---
-----------------------
LIST
RUN
SCR (scratch previous program)
SAVE ( user provided )
LOAD ( user provided )

--basic keywords---
-------------------
REM
IF THEN
TO
STEP
LET
GOTO
PRINT
INPUT
FOR NEXT
GOSUB RETURN
DIM(ension)
END

-- math operators ---
---------------------
INT SGN ABS SQR TAB RND CHR UDF

-- ERROR Messages ---
----------------------
SY syntax error
DE dimension error
OR out of range
IN illegal number
BG buffer or stack overflow
FA
DZ divide by zero error
FX fix
LE let error
IQ illegal quote
IF
UN undefined line
GS gosub error
RT return error
FE
FN for/next error
SQ square root error
AF array format error
 
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