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RE: [N8VEM-S100:2332] Non-Buffered Prototype Board and Front Panel Board

Steven, I sent a status update on our V2-SMB a few days. In case you dig not see it. Her it is again:-




Andrew and I have been working on a V2 System Monitor Board for some time.  Already have done one prototype but another is needed and is in the works.  FYI I am attaching a schematic.

The issue is mainly how much can you get on one board.


The current V2 has the following:-


Display 24 address lines with either a HEX display or Bar LED’s (cheaper)

Display 8 or 16 bit data lines coming into the current bus master in halt/single step mode

Set a hardware (24 switches) breakpoint anywhere in the current masters 24 bit address space so once the CPU accesses that location it halts and can be single stepped from there.

A Single step function.

Lower any combination of the 4 TMA(DMA) S100 lines so that in theory, up to 16 CPU’s could control the bus.

555 Timer generated (long) signals for reset and slave clear.

All address lines are now  latched so fast CPU’s like an 80386 can display valid data on the HEX display.

LED (stretched) light flashes and status signals for the major S100 bus status/control signals, (pWR*, SOUT, MWRT etc.).  These remain valid during single step mode.

A few other tweaks.


The only major IMSAI function not included is “deposit” and “deposit next”.  These were too difficult to add in a generalized manner independent of CPU speed (i.e. no single shots)  and can easily and better done via the current master/CPU monitor.


We are just doing a second prototype version and hope to have it in a few weeks.  I don’t anticipate any further issues but did not want to go for a final “production” run because there were numerous small changes on the previous prototype.   Should have it running in say a month. Stay tuned and keep an eye on this forum.


BTW, the main issue with older front panel boards and the FPMini board, jade board etc. is that they use LS123 single shots etc. to emulate signals. These simply will not work correctly with high bus speeds.  There are of course ways around that but it uses up board real estate.   For the SMB,  I make sure all signals are clock speed independent (e.g. latching address lines etc.).






From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of Steven Feinsmith
Sent: Thursday, February 6, 2014 11:00 AM
To: n8vem...@googlegroups.com
Subject: [N8VEM-S100:2332] Non-Buffered Prototype Board and Front Panel Board


I purchased four superb designed S-100 buffered boards few weeks ago and I was very please with it. I also interest to buy S-100 non-buffered prototype boards for my project that involve to clone from my aged Technical Design Labs boards (ZPU, SMB and Z16). I am sure that you may also need it for your future projects with wirewarp method.

I aware N8VEM needs to know how many of you may need to order the boards (I assume perhaps least 20 boards before can order the PCB). Please let Andrew knows if you desire to have the non-buffered prototype boards.

I am within few months left to start my S-100 system online for the first time since I ceased back in late of 1970's when I jumped into IBM PC then Apple Macintosh. I realize I still need to have front panel with "Christmas-like flashes". This will help me for troubleshooting. eBay is selling IMSAI mainframe completed with front panel cost a lot of money. Recently, someone is selling Jade front panel with long vertical board like an extender. But I aware it does not work well if S-100 system is running higher speed. There are FPMini board but hear nothing about it lately. Also nothing about S-100 System Bus Monitor. I have superb TEI 22-slot motherboard in original TEI mainframe with linear power supply. This power supply will replace with switching power supplies as same as what Andrew did with his S-100 system. Anyone of you may want to have front panel that can monitor the hardware with array of LEDs. It would be much nice if we can create next generation front panel that provide hexadecimal display (much like famous Heathkit H8 front panel with octal based display). It will be nice to have hexadecimal front keypad (again like Heathkit H8). The individual LEDs can be use on the panel for excellent troubleshooting.

Heathkit uses PAM-8, 1kB ROM (increased to 2kB)  contained monitor program to control the front panel and keypad. I believe I have information on PAM-8 monitor program somewhere in one of my hard drive based libraries. You can get more information and see picture of H8 computer at http://en.wikipedia.org/wiki/Heathkit_H8
In fact, my past experience with Heathkit H8 and H89 computers are far superb system during with high reliable during old days.  I had Heathkit H8/H89/H120 system along with TDL/Cromemco/IMSAI/ALTAIR plus other S-100 system were all stolen when I moved out from South Florida years ago.

Hopefully, you may like my idea to create Z-80 based S-100 and act like Heathkit system. I forward to hear from you and show your interesting with this kind of project.

Thank you,

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Attachment: Printing S100_SMB V2-Rerun 3-sch.pdf
Description: Adobe PDF document