On 1/4/2012 8:20 PM, Bill Sudbrink wrote:
> Josh Dersch wrote:
>> How does the "phantom" line work? I see references to this in some of
>> my S-100 manuals but I'm not clear how it works (who raises/lowers it,
>> when, etc...)
> It can be a little bit "implementation dependent" but usually there are
> cards that assert phantom (it is active low, there has to be a pull up
> on it somewhere (the CPU card I think)) and cards that "honor" phantom.
> When an address is presented to the bus, any phantom asserting card that
> whishes to override that address pulls the phantom line low. A phantom
> honoring card that would normally respond to the address will instead
> suppress any activity. Note that this system does not prevent multiple
> phantom asserting or phantom honoring cards from stepping on each other.
> Careful system configuration is still the responsibility of the builder.
> In the case of the Cromemco FDC cards, the FDC becomes a phantom asserter.
> Any RAM card that the system has that resides in the same address space
> ($C000-$CFFF in the case of a 4FDC) must honor phantom. The CPU presents
> an address to the bus, the FDC card does an address decode, determines that
> it is an address it wants to respond to and activates the ROM (the CE (chip
> enable) pin on the ROM is also active low) asserting PHANTOM at the same
> time, disabling the RAM card. When you deactivate the RDOS ROM with the
> poke to the I/O address, then the FDC card will no longer activate the ROM,
> PHANTOM will no longer be asserted and the RAM card will respond to the
> address previously occupied by RDOS. I run CDOS in a full 64K
> configuration this way.
>
> Bill S.
>
Thanks for the clarification! I do have a 32K Static RAM card that
seems to support the Phantom line, I'll have to play around with it once
I find something to fill the last 16K.
(Now I just have to figure out why I can't get the FDC to write floppies
correctly...)
- Josh
On Jan 4, 2012, at 11:20 PM, Bill Sudbrink wrote:
> Josh Dersch wrote:
>> How does the "phantom" line work? I see references to this in some of
>> my S-100 manuals but I'm not clear how it works (who raises/lowers it,
>> when, etc...)
>
> It can be a little bit "implementation dependent" but usually there are
> cards that assert phantom (it is active low, there has to be a pull up
> on it somewhere (the CPU card I think)) and cards that "honor" phantom.
> When an address is presented to the bus, any phantom asserting card that
> whishes to override that address pulls the phantom line low. A phantom
> honoring card that would normally respond to the address will instead
> suppress any activity. Note that this system does not prevent multiple
> phantom asserting or phantom honoring cards from stepping on each other.
This sounds a lot like the INHIBIT line on the Apple II bus. Is that roughly analogous?
- Dave
I have a "Thinker Toys Universal Interface Board" here, and I've been trying to figure it out. This is an early version of the Morrow Switchboard. It has a copyright date of 1978. The manuals available online are for the more common Morrow Switchboard, Rev 2. Comparing this board to a Switchboard reveals some subtle differences, but by and large, the boards are the same. This older version I have has no solder mask, while the Rev 2 has a blue solder mask. There are minor component placement differences.
The most drastic difference seems to be the comparators that read the switches at the top of the board. As found, the board had a LOT of trace cuts and jumps, and some traces just plain peeled off - all around those four LS266's at the upper right, directly under the SW5 and SW6. Attempting to figure out what was done is nearly impossible. The switches themselves are still connected to the 266's with factory traces, at least, most of them - but the rest of the inputs were a mess of wires with bad solder joints. Of course... it doesn't work, and the wiring of the switches doesn't even come close to matching the schematics. Not only that, the factory traces that remain don't match the schematics. I mean, the switches wouldn't even be in the same order. It's a mess.
So... does anyone have the schematics for this thing?
-Ian
During a cleanup of stuff at our company, some interesting items popped up
and which I could take home.
A device which emulates 2 tu-58's but then as 2 3.5" floppies,
2 complete 11/34a board sets + operator console interface & 64KW mem
one complete 11/24 (cpu. KT24, 128Kw mem)
a test unit for SMD drives (for CDC & RM02/3/5),
a spares kit for an LA-120/Decwriter III
a box full with all kinds of DEC loop-back test connectors
a crt testkit with 8 different tube connection boards.
Ed
--
Dit is een HTML vrije email / This is an HTML free email.
Dave Riley wrote:
> I shudder at the fact that many of our high schools use Java as an introductory language. I really can't see the point of starting someone out saying, "Your program runs from a special method in a special class (we'll teach you what both of those are later) labelled 'public static void main()'.
Just wave the chicken correctly, and maybe if you stick with it long enough, you'll find out what that magic incantation means."
Well put. Alas that was the situation I was facing in University, where Java was a compulsory assignment for all EE students (and thus probably their first encounter with programming for some of them).
I had hitherto only dabbled in various BASIC dialects (CBM, Borland Turbo, and Visual BASIC) - and NO, I don't feel like a brain-crippled Zombie! - but had read my share of C code too, so one of the instructors asked me whether I was a C coder - but probably just because I had picked up that style of abbreviated, mixed-case procedure and variable naming...
That however only came later, when I took a course "Systems programming in C". There at last, some really useful education about things like I/O, queues and scheduling (however *n*x-centric) started to happen - but that course was primarily targeted at grammar / high school level *teachers*! I was just barely allowed to take an oral exam and turn in the earned credits (an A-) for my diploma on a special agreement basis.
A while later, I also got some exposure to FORTH when I started hacking around on Sun workstations, like modifying their boot net routines (to get away from the RARP requirement that some OBP revisions imposed) and adding support for nonstandard frame buffer resolutions.
(BTW, anybody here been into the cgthree ASIC deep enough to tell me whether it can do interlacing and if so, how to frob it to?)
I did also got to write some assembly for an AVR microcontroller in my pre-diploma thesis.
Arno Kletzander
...sent from my HTC Magician PDA
I grabbed a copy of a free (!) publication from the Cryptologic Museum
entitled "The start of the Digital Revolution: SIGSALY - Secure Digital
Voice Communications in World War II". It mentions that you can visit the
library and look at "The Green Hornet... America's Unbreakable Code for
Secret Telephony" -- privately published in 1999 by D. E. Mitchell. It
says it is very complete.
And yes, the museum only has a mock up. But when you consider the noise
disks, it's an amazing feat.
Hi! One of the lesser known N8VEM home brew computers is the ECB
mini-M68000 board.
Presently it runs TUTOR 1.3 and we are planning on porting CP/M-68K
Here is a description of the computer. It connects to the ECB bus to use
various other home brew computer peripherals.
http://n8vem-sbc.pbworks.com/w/file/48863865/baby%20M68K%20descr.txt
All of the information is public and freely available. The PCBs are $20
each plus $2 shipping in the US and $5 elsewhere.
http://n8vem-sbc.pbworks.com/w/browse/#view=ViewFolder¶m=ECB%20mini-M680
00
If you would like to build one of your own mini-M68000 please contact me at
LYNCHAJ at YAHOO.COM
The main discussion on the mini-M68000 is on the N8VEM mailing list
http://groups.google.com/group/n8vem
Thanks and have a nice day!
Andrew Lynch
