DPS-1 Ithaca Intersystems CP/M distribution

This page last updated June 28 2013, notes added April 3 2016. This page discusses an 8-inch disk I reconstructed, of an UNTESTED distribution of Ithaca Intersystems DPS-1 CP/M 2.2, Ithaca version 4c. This is work in progress and notes in progress.

However, the disks I created may not have worked. See my warning below. - Herb

For S-100 items on my site, go to my S-100 home page To contact me, please follow this link for ordering information, terms and conditions, and info about orders outside the USA.

Warning: this disk image fails to boot, check my alternative

In March 2014, I sent Kipp Yeakel, who had a working and booting DPS-1, one of my physical disk copies of the SSSD 8" "boot disk" described and offered on this Web page. It did not boot. But Kipp constructed his own SSSD 8" disk, from his own DSDD disks, and THAT booted up. He sent me copies. But I was not able to work on this, until I restored a DPS-1 system to operation, in March-April 2016. Go to that linked Web page for working Ithaca CP/M related files, and discussion. There's files for the Ithaca DPS-1 disks I produced, and from a disk from Kipp, which both successfully booted on my working DPS-1 systems. The page describes the board setups, compared to setups in the Ithaca manuals. - Herb

Ithaca DPS-1 CP/M distribution

Ithaca disks used to create files and distribution disk

In Feb 2013 I recreated a distribution of Ithaca Intersystems DPS-1 CP/M 2.2, Ithaca version 4c. In June 2013 I set up this Web page to describe that distribution and to make a ZIP file of it also available. To create the 8-inch SSSD diskette I'm distributing as Ithaca "version 4C", and the files in the corresoponding ZIP file dps_v4c_cpm.zip, I extracted those files primarily from an 8-inch SSSD disk I call "cpm_ith1", but I also referenced files from a similar disk I call "cpm_ith2".

Both disks have same versions of T(iny)BIOS.SRC, ISTARTUP.SRC, ISTARTUP.COM/.CPM. (TBIOS.CPM on disk ith2 is broken.) Both disks have the same boot track binaries, the same small BIOS binaries.

Both 8-inch disks are Single Sided Single Density or SSSD, with 26 X 128-byte sectors. Consequently the boot tracks are 54 X 128 bytes long and are in simple sequence. The first directory sector on 8" SSSD is track 2 sect 1. For the most part, 8" SSSD 26 X 128 sectors are a distribution standard for CP/M; there's a logical interleave of 6 between sectors, so the operating sequence of sectors from the physical enumeration is "1, 7, 13, 19, 25, 5, 11, 17,....." (I think.).

cpm_ith1 disk was labeled "Standard BIOS Version 4c". File trk01.bin was read off boot tracks 0 and 1, using DU (Disk Utility, available from the CPMUG and SIG/M distributions) on a Zenith Z-100 system running CP/M-85. Files were accumulated onto a 5.25" CP/M diskette and eventually transfered to my desktop computer and my site. The Z-100 was also used to create a 8" SSSD CP/M disk which became my "master copy", and to create subsequent 8-inch copies.

cpm_ith2 disk labeled "w/cache BIOS version 4h" was used to verify by binary comparision the same file and boot tracks on cpm_ith1 disk. The boot tracks of "cpm_ith1" match byte-byte with boot tracks of disk identified as "cpm_ith2". I'll discuss the "4h BIOS" version later below.

UNTESTED: Since as of May 2013, this re-created diskette was not actually "booted" or tested on a DPS-1 system, I cannot say with confidence it can be booted from a DSP-1 system. COpies are in the process of being tested, and in due course I'll test it on my own DPS-1 system.

TDL type Z80 mnemonics Ithaca Intersystems apparently uses some form of TDL type mnemonics for their Z80 sources. Ithaca provided an assembly language toolset at extra cost - there's a minimal assembler included. Technical Design Labs was first (at least early) to produce Z80 cards for S-100. They devised an extension of Intel 8080 mnemonics (instruction names) for the Z80; Zilog who created the Z80, developed their own mnemonic scheme. This Web page discusses TDL and their Apple and Zapple monitors and their TDL mnemonics. I have not confirmed that the Ithaca Z80 code "matches" TDL's standards.

How does a DSP-1 boot up?

Briefly, the DPS-1 system has a boot ROM which is executed on reset. That ROM reads the first sector of the first diskette. There's encoded information which informes the ROM to read the rest of the sectors on the early tracks. Those sectors contain CP/M binaries CCP, BDOS; plus a "tiny BIOS" compiled from a TBIOS.SRC file. The CCP has an embedded command to load and run "ISTARTUP.COM", which contains a larger BIOS which becomes the operating BIOS for CP/M.

read this note bootup.txt for further details.

Files on disk and ZIPed version

WARNING: The disk and image described below may not be successful - read the linked warning.

Disk files below and 8" disk as distibuted are from "version 4c" disk I call cpm_ith1. On the ZIPped version of the accumuated files the files "*.cpm" from the diskettes version are files "*.com"; that standard renaming occurs with 22DISK transfers. DRI below refers to Digital Research Inc. and their "standard" CP/M 2.2 set of files.

ASM.CPM		DRI assembler, Intel 8080
ASMBIOS.CPM	Ithaca assembler for BIOS, TDL mnemonics
COPY.CPM	Ithaca copy program
DDT.CPM		??? debugger
DEBLOCK.ASM	DRI sample deblock 8080 code
DISKDEF.LIB	DRI sample 8080 code
DUMP.ASM	DRI sample file dump pgm
DUMP.CPM	DRI sample file dump pgm
ED.CPM		DRI text editor
IFORMAT.CPM	Ithaca disk format, copy pgm
ISTARTUP.CPM	Ithaca, at boot brings in larger BIOS
LABEL.TXT	description of 8" disk label for dps1 diskette
LOAD.CPM	DRI load-hex pgm
MEM.CPM		Ithaca memory test pgm
MEM.DOC		Ithaca memory test pgm
MOVCPM.CPM	DRI/Ithaca pgm to resize CP/M
PIP.CPM		DRI file copy pgm
SBIOS.SRC	Ithaca source for ISTARTUP
SEEK76.CPM	very small program...?
SET.CPM		Ithaca pgm to modify ISTARTUP
STAT.CPM	DRI file status pgm
SUBMIT.CPM	DRI batch command pgm
TBIOS.CPM	Ithaca BIOS binary, also in boot track 1
TBIOS.SRC	Ithaca BIOS source
tk0.bin		binary of track 0 on 8" SSSD disk
tk1.bin		binary of track 1 on 8" SSSD disk
TRK01.BIN	binary of track 0, 1 and directory sector
XSUB.CPM	DRI batch program

on the 8-inch SSSD diskette, track 0 contains the binary of file tk0.bin, and track 1 contains the binary of file tk1.bin. Track 2 has the CP/M directory sectors and subsequent tracks have the above files.

Comments on disk files

tk1.bin includes a "tiny BIOS" binary, which is used when CP/M is loaded to call "istartup.com". Source for that BIOS is TBIOS.SRC. The istartup program contains the larger BIOS used by the running system. The source for that BIOS and istartup is SBIOS.SRC.

The BIOS binary on the track 1 image, is VERY similar to the binary version of TBIOS.COM (.CPM) on the disk/ZIP file. A visual binary compare, shows differences only in some bytes which suggests a consistent difference in ADDRESS beween the two. The binary on the tk1, has addresses 0xF8** and 0xF5**; the file TBIOS.COM has addresses 0xF6** and 0xDA**. I cannot guarantee these are the ONLY differences.

FBIOS from "cpm_ith2" disk

FBIOS_4H.SRC is a version 4h Aug 1981, of SBIOS which is version 4c for July 1981. On my site it will be FBIOS_4H.SRC.

Version 4h (FBIOS) seems to include some differences in front panel light and switch behavior. Also, some kind of problem behaviour with control-W and buffers. I've not read much further than that.

Additional files on site

BOOT.ASM is the source for the ROM boot. I ought to assemble it so there's a binary file, so it can be compared to the actual boot on the DPS-1. But there is an asssembled listing of this, I believe, in the Ithaca manual.

bootup.txt is a description of the details of the boot-up process, which names files and locations on the boot tracks and so forth.

Other Ithaca disks

As of March 2014: The disk and image described above may not be successful - read the linked warning

Work is in progress, to read and recover files from other diskettes. I hvae a Ithaca "5g" disk with some files. I have a set of "Pascal Development System" diskettes from 1980. Also something called "Interproof". Thanks to John King I have some additional Ithaca disks. They include a "PICO.SRC" which is a another "tiny BIOS" which to a first order looks the same as TBIOS.SRC. My analysis of John's disks, informed me enough to look over other Ithaca disks I had; I used those disks to extract files and rebuild what I hope is a bootable DPS-1 diskette.

The Rhode Island Computer Museum acquired a DPS-1 in 2013. They briefly had a bootable CP/M 2.2; then the system failed to boot. Michael said "We were able to set breakpoints with the front panel and stop the boot process. We then single stepped the boot code to see what it was doing. Sometimes it looks like it loaded CP/M, sometimes it looks like it gets stuck when talking to the diskette controller. We will eventually figure it out and get it working again." Courtesy of Al Kossow of Bitsavers.org, they successfully "imaged" one of the RICM boot diskettes. here's one such image at one mirror of bitsavers.

- Herb Johnson

Herb Johnson
New Jersey, USA
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