1 Nov
1999
1 Nov
'99
2:43 p.m.
The same thing was "wrong" (meaning that it irritated me and offended my
sense of how things should be) as with the N*, in that they used memory
space I wanted to use. Consequently, I never seriously used, nor did I ever
promote them. It was no big deal, but at the time I thought that it was.
Dick
-----Original Message-----
From: Dave Dameron <ddameron(a)earthlink.net>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Monday, November 01, 1999 6:40 PM
Subject: Re: Northstar Horizon
At 10:52 PM 10/31/99 -0700, Richard wrote:
>There certainly were a few vendors whose systems were as much off-center
as
>the N*. Just take a look at Vector Graphics'
systems, for example. I
once
owned a couple
of those, with their memory-mapped video refresh memory.
What was wrong with their "flashwriter", at least for that time, late
1970's? It was very similar to the Processor Tech's "VDM", and cost a
whole
lot less than a text VDU. You could move its location in memory if desired,
but had to have matching drivers.
-Dave
1 Nov
1 Nov
11:22 p.m.
The same thing was "wrong" (meaning that it
irritated me and offended my
sense of how things should be) as with the N*, in that they used memory
space I wanted to use. Consequently, I never seriously used, nor did I ever
promote them. It was no big deal, but at the time I thought that it was.
My solution was far more reasonable. Map it <VDM1> at 4000h and set a bit
to enable it (small hack). That way it used no TPA space and was still
faster than using a TTY. I later set up one of the NS* controllers that
way for a full 64k space. Of course I had to write my own drivers but it
was pretty trivial.
Allison
2 Nov
2 Nov
4:29 a.m.
Allison wrote:
My solution was far more reasonable. Map it
<VDM1> at 4000h and set a bit
to enable it (small hack). That way it used no TPA space and was still
faster than using a TTY. I later set up one of the NS* controllers that
way for a full 64k space. Of course I had to write my own drivers but it
was pretty trivial.
And hack the RAM board to be disabled when the VDM1 is enabled?
6:02 a.m.
My solution
was far more reasonable. Map it <VDM1> at 4000h and set a bit
to enable it (small hack). That way it used no TPA space and was still
faster than using a TTY. I later set up one of the NS* controllers that
way for a full 64k space. Of course I had to write my own drivers but it
was pretty trivial.
And hack the RAM board to be disabled when the VDM1 is enabled? 
6:43 a.m.
New subject: S-100 phantom (Was: RE: Northstar Horizon)
Ah, ever hear of phantom... part of the MDS-A and VDM
IO hack was to set
them up to output Phantom, in both cases it was just a jumper required.
The disable was simpler, MDS-A has a rarely used sector interupt enable
latch and the VDM used a bunch of bits for windowshading, something I
considered useless and removed from the board (a few socket level jumpers)
and I had the bit I needed for enable. If they were enabled phantom was
generated, if they were not ram was there.
I'm getting to this point with my IMSAI restoration. The
ROM on the Cromemco 4FDC can be disabled via an I/O
write... the SDS Expandoram will enable/disable based on
phantom (line 67). Unfortunatly, this seems to control the
whole board. How was phantom used historically? Are there
common boards which generate phantom as factory built? I'm
now using a Cromemco ZPU which seems to work fine, but I have
no docs for it. Does it have a "phantom latch"?
Thanks,
Bill Sudbrink
7:09 a.m.
New subject: S-100 phantom (Was: RE: Northstar Horizon)
Yes, Phantom/ was generated by a lot of cards. The mech for it was if
that card was enabled (in an IO latch) and it's address came up it would
assert (active low) phantom/ and kick everyone off the bus for that cycle
and if the board didn't select it was not an issue.
So My Compupro RAM16 (64k static) in the NS* (system A) has all banks
enabled and if we hit e800H the FDC forces phantom/ and the ram16 is
deselected for that address.
Allison
On Tue, 2 Nov 1999, Bill Sudbrink wrote:
I'm getting to this point with my IMSAI
restoration. The
ROM on the Cromemco 4FDC can be disabled via an I/O
write... the SDS Expandoram will enable/disable based on
phantom (line 67). Unfortunatly, this seems to control the
whole board. How was phantom used historically? Are there
It would but only if the board like the 4FDC asserted phantom/
when the rom is active. The fact that the board (expando)
is board level selected is unimportant as Phantom/ is a DESELECT
that is generated by some other card using the same space.
It is possible (and was done) to use phantom/ for memory banking
such that if a bord generated phantom/ it didn't look it at (or it get
circular). I used that trick with 4 16k static cards all jumperd for
0000-->3fffh range. Only one would be active based on a selct register
and they would kick off the main 64k ram card when their addresses were
active. from a software perspective that gave my 5 16k banks all starting
at 0000 and 48k of main ram that was allways the same(common). It was my
first banked system and allowed background tasks running in each of the
16k banks (also caches, extended bios and extras).
common boards which generate phantom as factory built?
I'm
now using a Cromemco ZPU which seems to work fine, but I have
no docs for it. Does it have a "phantom latch"?
Most of the CCS, Compupro, Cromemco and others that were post 79ish did
use and respect that signal. However early ones (all MITS and IMSAI)
didn't use that signal at all. by 1981 it was defacto useage for roms and
memory mapped Video ram, FDC or other.
Allison
7:51 a.m.
New subject: S-100 phantom (Was: RE: Northstar Horizon)
So My Compupro RAM16 (64k static) in the NS* (system
A) has all banks
enabled and if we hit e800H the FDC forces phantom/ and the ram16 is
deselected for that address.
Ah... I see... Now, the 4FDC does not have any connection to
pin 67, so it is not using phantom. But it should be easy to
implement... Can I just take the /CS (-NOT- chip select) pin
from the 2708 and wire it to 67? Maybe I need to -NOT-
it first?
Thanks
8:10 a.m.
New subject: S-100 phantom (Was: RE: Northstar Horizon)
So My Compupro
RAM16 (64k static) in the NS* (system A) has all banks
enabled and if we hit e800H the FDC forces phantom/ and the ram16 is
deselected for that address.
Ah... I see... Now, the 4FDC does not have any connection to
pin 67, so it is not using phantom. But it should be easy to
implement... Can I just take the /CS (-NOT- chip select) pin
from the 2708 and wire it to 67? Maybe I need to -NOT- it first?
8955
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7 comments
4 participants
participants (4)
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allisonp＠world.std.com -
bill＠chipware.com -
edick＠idcomm.com -
eric＠brouhaha.com