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Latest IMSAI Series Two Status- 4-20-2004

Howard and I haunted the aisles of the Embedded Systems Conference in San Francisco earlier this month and were both under whelmed and inspired at show's end.  After much deliberation over the past couple of months we have decided to use the Zilog EZ80 processor as a core for the MPU-C processor in the new Series Two.  It provides faster speed and, most importantly, an ethernet port which allows connectivity to the internet and other devices connected through a network using ethernet protocol.  We will be placing the processor and support ram on a "daughter card" which will in turn plug into the S-100 "base" board.  By using this approach we can develop alternative processor designs without having to change the "base board" layout.  This new design will be incorporated and offered at no additional charge to all Advance Offer participants.

While compromising several obscure features of the original IMSAI 8080 design related specifically to the Intel 8080 microprocessor chip, the overall benefits and performance far outweigh the compromises.

A major change in the Front Panel design involves the addition of a USB hub and front panel access for the "A" and "B" connectors utilized with auxiliary USB devices.  Most importantly, the function of switches and LEDs on the front panel can be programmed by the user for alternative actions and displays, optimized for specific applications.  What this means is that the Front Panel is no longer bound only to S-100 bus utility, but can be used as a programmable front panel for PC use as well, either with an optional internal ATX motherboard, or with an external PC.  As an example of utility, those who have touted the "superiority" of software emulators can now have a real front panel (as opposed to the virtual front panel) to integrate and work with.  Another application would be to allow use of the front panel switches as portals to application software; flip a switch to bring up your word processing software, flip another to bring up spreadsheet applications, etc.  Program the ap to fit your needs!

It's our feeling that this approach will broaden the interest in our Series Two design to the PC market, including those folks seeking a nostalgic "skin" for their system as well as others interested in exploring and utilizing the wealth of hardware and applications available for the venerable S-100 bus.

We are using a split-board design that keeps the USB and intelligence on a smaller board, and a connector scheme to interface to the S-100/switch/LED board.  One vision of the near future would be the substitution of a touch screen LCD or plasma display for the LED/switch section.  We witnessed a number of suitable products that would interface nicely with our proposed architecture at the Embedded Systems Conference.  Envision wide screen digital video displayed on the front panel; we saw a number of applications running at the conference, all implement-able with our design.  Adaptability of design is seemingly limitless.

As we began to envision larger potential for user base growth specifically using PC-only applications, this led me to cut 6 1/2" off the front of one of our IMSAI Series Two base plates, file and punch a few holes, to yield the proposed SK (short chassis) enclosure which may be configured for either S-100 or ATX (PC) motherboard applications.  The mounting holes in the sheet metal accommodate either installation, just as the full-size Series Two enclosure does.

Rack mount applications still seem to draw users, so we're working on a 5U (7 1/2") height bracket/panel mask kit to allow rack mount of all legacy and current IMSAI systems with our standard 17" width.  If you have an interest, let us know and we'll accelerate this project.

The IMSAI Super I/O board  $350

Revised specifications for the IMSAI Series Two Super I/O and MPU-C (click here)

The problem of boosting voltages from a stock ATX power supply to accommodate the S-100 bus is nearing an end after much hair pulling and being told: "You can't get there from here" by "experts" and factory tech reps.  Here's a photo of the first prototype:

I've mounted the PS-B booster/distribution board on the back of the front sub-panel in the same fashion as was implemented on the very first IMSAI 8080's where the rectifier/regulator board was originally mounted.  The 20-pin power connector from the ATX power supply plugs into one of the mating receptacles on the board, then a jumper cable feeds power to the optional ATX motherboard.  A second cable feeds the regulated +7.5, and +-14.5 volt output voltages to the Series Two EXP-9AT motherboard.  The design needs some fine tuning but seems to be workable despite dismal predictions by others less driven (or obsessed!).

The EXP-9AT motherboard has also been redesigned to incorporate a novel active termination scheme promoted by Texas Instruments.  We have abandoned the older adjustable termination voltage scheme once used by Godbout and Morrow Designs in favor of the TI "weak latch" approach that is widely used in PCI and other fast bus systems.  Although we haven't received our new prototype boards as yet for testing, we're confident that we will have solved many of the stability and performance problems that have plagued S-100 bus users over the years with a reliable high speed design.  Much of this redesign effort is the direct result of Howard's work with our volunteer developers working with the Super I/O board in various configurations using legacy processor and memory boards.
 

Regarding Software Development-  Howard has a comprehensive resource of information, references, source code, and links regarding the Super I/O board on his web site at http://www.cpm80.com/superio.html.  He has successfully brought up and partitioned hard drives through the  IMSAI Super I/O IDE interface, and has now developed CP/M-compatible format and storage utilities for low-cost IDE Compact Flash memory devices using a low-cost IDE card reader/writer.  This reader/writer is an attractive Four Slot IDE All-In-One reader which allows the user to read/write all standard flash medias one at any time. It works with the IMSAI Super I/O board IDE interface. We are offering this item bundled with cables and support software and utilities as a reasonably priced memory storage option (an alternative to hard drives) for purchasers of the new IMSAI Series Two and Super I/O boards.  The complete add-on card reader package is $50.  Please e-mail us for additional information or comments on this offering.

 

Further Development-  We currently have six volunteer software developers who are working under Howard's guidance to provide supplemental code and to clean up some of the preliminary Super I/O board support code written by Howard.  The goal is to provide a diverse and rich body of open source utilities and application software to enhance the capabilities of the new IMSAI Series Two.  The following is a copy of an e-mail that Howard sent to one of the respondents:
 

Hi Michael,

Thanks for your interest and for sending your resume.  We still have a couple of hardware issues with the Super I/O board.  When those are resolved, we'd like to send you a prototype and some source code to work on.  I have some stand-alone (HEX downloadable) programs to format IDE drives, partition them, and boot them.  All this code needs to be cleaned up, optimized, and made rom-able, so we can pre-load it on the FLASH memory device on the I/O board.

In addition, we want to provide CBIOS source code for CP/M 2.2, CP/M 3.0, ZS-DOS, and eventually MP/M and UZ80 (Unix for the Z80) and whatever else we can find to run on the Series Two.  If you have an 8086-based processor board, it would be neat to have drivers for CP/M-86 for this board.  We're looking for someone who wants to participate on the hobbyist level, and we are willing to provide prototype hardware, and discounts on the real hardware when available.

We require that all source code developed for this project is released either to the public domain, or under the GNU Public License.  We are providing our source code under those same terms, in the interest of promoting an open-source, open-architecture machine, and to add to the educational value of the Series Two.

If you are interested in helping in any of these areas (or can think of any other things you'd like to do,) please let me know.

Thanks for your interest,
Howard

 


A view of the internal layout of our production prototype.  The ATX motherboard is my old Soyo Pentium 3 which was recently replaced with an ASUS P4T.  The newly revised IMSAI EXP-9AT S-100 motherboard prototype, visible in the front, has not had it's active termination components installed yet in this photo.

This image shows the IMSAI EXP-22 motherboard installed in the base plate to illustrate  compatibility with the original IMSAI 8080 configuration.  Holes have been included for use with the original IMSAI PS-28 power supply board as well.  Please note that in this "proofing" shot, the base plate has not had the flanges formed or PEM fasteners installed, since this was a fit-up test for the "first article" sheet metal.


Power Supply-  (this is old, but still relevant)
Howard and I are both running over-clocked Pentium 4 motherboards.  I chose the ASUS P4T533-C, since this is a later version of what Howard's using.  Since most of the latest Pentium class motherboards require an additional 12 volt connector to supplement board power (referred to as the 12V specification), we strongly recommend upgrading the power supply to a minimum 450 watt unit if equipping the system with one of these later boards.  I'm currently (no pun intended!) using an Enermax 465 watt supply in my system, and getting 2.41 GHz. performance with a 1.8 GHz. Pentium 4 with stock heat sink/fan combo, and using 40 ns. RAM.  The performance is remarkable, and everything seems to be running with no noticeable increase in temperature.  Upgrading from a Pentium 3 to the Pentium 4 did require doing a fresh install of Windows 98 (I'm a diehard when it comes to operating systems), and having to reinstall all of my Windows-based software, but it was an excuse to create a new registry, replacing the huge original I've carried since my upgrade from DOS to Windows 3.1.  It's amazing how much legacy junk can gather over the years!

We offer the premium Enermax 550 watt power supply as an option so, if you're considering an application such as Howard's and mine, you might want to upgrade your order.  I originally had chosen a 520 watt supply for the upgrade, but have since upgraded to a 550 watt supply made by Enermax.  This supply costs about $50 more than the earlier choice, but reviews about the quality and reliability of the Enermax supply have convinced me that it is the superior choice.  As a result, the power supply upgrade option (option 4) is $110 additional.

The IMSAI Series Two features an auxiliary power supply board that the ATX power supply plugs into.  A small cable runs from the CPA Front Panel board for controlling the remote on/off function of the ATX power supply.  The auxiliary power supply board also provides a power supply cable that plugs into an optional ATX internal motherboard.  The +5 volt and +/- 12 volt supplies are tapped by boost circuitry to provide the necessary +8 and +/- 15 volts necessary for the S-100 bus. 

The IEEE-696 S-100 specification for power distribution is:

+8 volts Instantaneous minimum must be greater than +7 volts, instantaneous maximum less than 25 volts, and average maximum less than 11 volts.
+16 volts Instantaneous minimum must be greater than 14.5 volts, instantaneous maximum less than 35 volts, and average maximum less than 21.5 volts.
-16 volts Instantaneous maximum must be less than -14.5 volts, instantaneous minimum greater than -35 volts, and average minimum greater than -21.5 volts.

I've kept the S-100 voltages toward the minimum side of the specifications to achieve better efficiency and to reduce thermal buildup, while ensuring good noise immunity through the S-100 board regulators.  The tentative Series Two S-100 supply is:

+7.5 volts @ 14 amps

+15 volts @ 2 amps

-15 volts @ .5 amps

Summary-
I'll update this page as needed as we near the final shipping date.  Thank all of you for your patience and understanding... the IMSAI Series Two is a reality!

-Thomas "Todd" Fischer (with thanks, as always, to Howard Harte)