This document copyright Herbert R. Johnson 2007, except quotes from Richard Cini are under his copyright. Updated Oct 8 2008. Contact and email information can be found in this notice.
The Home page for all my CP/M and Digital Research Web pages and information is at this link. To go to my S-100 Home page click here.
During November 2007, Rich Cini posted in comp.os.cpm that he was looking for assistance with his IMSAI system, which included the Icom "Frugal Floppy". I recognized that as a very early, pre-CP/M and pre-S-100 floppy disk controller and drive product. I asked Rich about it; his reply is below with his permission, as is a copy of his list of documents which are also on his Web site. - Herb Johnson
Herb: If you want [ICOM] manuals, just look on my Web site. I scanned everything I had relating to the iCOM system.
Note 10/2008: Rich's ICOM work is now found via this WEb link.
As far as what it actually looks like, there are some pictures embedded within the manuals, but the drives are in a HUGE cabinet that's roughly the same footprint as my IMSAI but taller. It connects to the IMSAI through a 50-pin red ribbon cable. The interface card on the S100 side is labeled "8800 Interface". On the board, there's a bunch of TTL, an EPROM and SRAM.
The system uses Pertec (Altair-style) FD400 drives. The Percom FD400 drives are soft-sectored and use standard IBM-format 8" disks. The actual disk system is manufactured by Synetic Designs Company (model FDS-2, serial 1154). The box contains three power supplies -- basically one for each drive and one for the controller/formatter. There are two very large PC boards in the case which does all of the drive control. All TTL logic -- no LSIs. There are no dates on the case and if I had it opened, I could look at the dates on the TTL.
The date of the software in the manual is 1977. The schematics are dated January 1977). The actual iCOM manual says "Rev. October 15, 1976". The controller board manual says "November 1975".
I wish I had a copy of FDOS. I have lots of floppies downstairs and if there's one, I'll let you know. I don't remember seeing one, though.
- Rich Cini
Note: by Jan 2008, Rich restored his IMSAI to operation using not the iCOM floppy controller and FD 400 drives, but a Compupro Disk 1A controller and Teac FD-55GRF 5.25 inch drives. Read this document by Rich for details about how he generated a new CP/M for that system.
The following is quoted from Rich Cini's site: go there for the actual PDF's. - Herb
IMSAI [by Rich Cini]
I have an IMSAI 8080 machine in my collection as well. The IMSAI could be considered to be the first "clone" machine, in this case, of the Altair 8800. It was configured similarly (8080 CPU and 4k of SRAM) but it had a splashier front panel and larger, bi-color paddle switches on the front panel. The power supply was larger and less noisy, and the backplane was better designed than the Altair.
My system didn't come with the stock 8080 CPU card installed (although it was provided). Rather, it came with the TDL ZPU Z80 CPU card (replacing the CPU card was a common upgrade as the Z80 became more prevalent). It came with 48k of installed memory in three 16k boards. The disk drive system was the iCOM "Frugal Floppy" system. The serial card is a Solid State Music 2p-2s card.
Manuals relating to the hardware installed in my machine
* CPU: Technical Design Labs "The ZPU Manual" (pdf) * Memory: 3 @ Vandenberg Data Products 16k SRAM (pdf) * Terminal board: Solid State Music 2p-2s (pdf) * EPROM: Solid State Music PB-1 (pdf) * Modem: PMMI Communications MM-103 Modem and line coupler (pdf) * Disk Drive System: iCOM "Frugal Floppy" dual 8" drive system. o iCOM Frugal Floppy CP/M 2.0 Supplement (Computer Mart of New Jersey-Bruce Ratoff) (pdf) o iCOM CP/M System Upgrade release notes (pdf) o Customized CBIOS3 listing for CP/M 2.2 and the iCOM Frugal Floppy (last date 4/22/81) (pdf) o CBIOS for CP/M 2.2 and the iCOM Frugal Floppy (might be for my system) (pdf) o iCOM Warranty Card (pdf) o Application note: Shadow Modification for iCOM Interface Card (pdf) o Synetic Design Company FDS-2 Binder: + Synetic FDS-2 Core Manual (pdf) + Operator's Guide - FDOS-II (pdf) + Operator's Guide - iCOM Macro Assembler (pdf) + Operator's Guide - Text Editor (pdf) + FD360/FC360 Controller/Formatter Maintenance Manual (pdf) + FD360/FC360 Schematic Diagrams (pdf) + Interfacing Guide for the FD360/FC360 Controller/Formatter (pdf) + BASIC-M Operator's Manual (pdf) - Rich Cini
An early ad by iCOM was in Electronics Design magazine for Sept 27 1974 - before the IMSAI and Altair were available. That ad claims it is the "first floppy disk peripheral for microcomputers". refers to the FD360 dual floppy system and Pertec 8-inch floppy drives. The controller had a parallel type of interface, to cards provided for various systems of 1974, microprocessor or minicomputer. No software or OS was mentioned. I discuss early floppy controllers in my CP/M Web site section, in this outline of CP/M development and history. - Herb Johnson
[I wrote this after reviewing Rich's document set. - Herb Johnson, Nov 2007]
Synetic Designs Company of Pomona CA offered the FDS-2 system. It supported up to 8-inch floppy drives with single-density, single-sided "IBM 3740" format. The controller was the iCOM FS360 Frugal Floppy Disk controller, a two-card (15" X 7") controller and a small "mux" card, enclosed with power supply and floppy drives. iCOM also provided an operating system called "FDOS II" for the 8080. The controller card set had an interface cable to another card which connected to the desired system. For the IMSAI/Altair bus, that was an S-100 interface board, possibly coming from Synetic. Synetic provided a "SDCEX" Executive handler which resided with FDOS. (iCOM also had a 6800 version of their FDOS.) There are references to the CF360 and FD360; these appear to all be the same hardware design.
Dates in the documents suggest the SDC Executive FDS-2 was written as late as 1977; a portion of the code is source-listed in the manuals. An XGEN program allowed modification of the executive.
The iCOM FD360 schematics manual is dated March 1976. It has schematics for the two controller cards 200028-200 dated 1-14-76 and -201; the mux card 200012-200 dated 5/5/76 and initialed "P Sen" or "P Sem". The Altair/IMSAI "8800 interface" schematics are 200057-200 dated 9/22/76 and initialed "J. Fazio" and "SWG"; they are not identified as "iCOM" and are drawn very differently. There are also two sets of Pertec schematics for the drive electronics. The two-card controller uses all small-scale TTL chips, no microprocessor. Therfore much of the logic was implemented in hardware, running at 10MHz clock rates - much faster than any microprocessor available in 1976. The "8800 interface" board consisted of input and output Intel 8212-type parallel ports, plus some ROM and RAM to support the operating system code including "boot" code. There are also floppy drive schematics, two sets.
One iCOM manual is "Operator's Manual iCOM Microperipherals (TM) FDOS-II for SBC/8800/Altair/IMSAI/Poly88" and dated "Rev. Oct 15, 1976, (c) September, 1976". That dates the FDOS-II software documentation. The docs refer to "Altair or IMSAI bus compatible", an old term for S-100 systems. FDOS-II resided at C400 and up as a series of jumps to routines. A monitor program in ROM loaded the rest of FDOS from diskette. But this system of Rich Cini's also included a version of CP/M.
One set of floppy drive schematics refer to the Pertec "FD BASIC II DC", 600320 or 600321. The schematic shows revision A was in 10/14/1975 in pre-product release, referring to the "200 FB"; revisions are dated to 5/76. A second set of schematics for 1978 and 1979 show Siemens AG apparently provided or designed a "FDD100-8D" drive. Either set shows the digital interface to the drive's hardware, like any other floppy drive.
A Maintenance document refers to the "Pertec FD400 floppy disk drive", at $650. The Controller formatter card pair was $850, the mux card another $50. Cables and power supplies added another $550. The interface card is not included. These are September 1975 prices; in that year you could buy a Ford Granada for $3700, a Mustang II for $4100. In other words, one of these floppy drive systems was about 1/3 the price of a new car.
A "BASIC-M" was provided by iCOM. I do not know if this was derived from Gordon Eubank's BASIC-E; Eubanks is not mentioned in the manual for this software. OTher software and manuals include a text editor, macro assembler. These date from 1976, 1977. CP/M 2.2 CBIOS dates from 1977, 1978, and 7/1980 as a set of source listings. These and other documents came from "Computer Mart of New Jersey" and were authored by Bruce Ratoff.
I conclude the S-100 interface was designed on or before Sept 1976; and the iCOM drive controller was designed on or before March 1976. The Pertec drives were designed before Nov 1975. But this collection of hardware and software was put together well after that date, given other documents' dates.
It's likely that Rich's hardware is close to what iCOM advertized in in this ad for January 1976 in Computer Design magazine; then iCOM designed an Altair card soon afterwards. Later they or someone offered a CP/M version. However, iCOM offered a similar or the same floppy controller as early as September 1974, given this ad in Electronic Design.
--reviewed by Herb Johnson
Copyright © 2008 Herb Johnson