Ampro "Little Board"

[Ampro Little Board]

In 2010, I obtained an Ampro Little Board Z80 system card, and built a dual floppy system around it. I created a Web page at the time about it. I've had correspondence about the product, and included it on this page. Most recent revision date July 17 2021. Contents Copyright (C) Herb Johnson except for material produced by others as named. This is one of a number of vintage computer restorations I've done.

Ampro "Little Board"

Late March 2010, I went to the Greater Baltimore Hamboree & Computerfest, commonly called "Timonium" after the local town. At the outdoor fleamarket near the end of the first day, I obtained an old ISC brand (Intelligent Systems Corporation) Intecolor S-100 system, built inside a color TV monitor. But inside that monitor was also an Ampro Z80 single-board computer called the "Little Board". This product was a kind of response to the "Big Board" Z80 computers of the era, board which were the same area as an 8-inch floppy drive. The Little Board fits under a 5.25-inch floppy drive. (Note: a modern Ampro "Little Board" is a Pentium class embedded computer.)

Ampro Incorporated has the additional distinction of producing the first "PC-104" embedded PC-compatible systems, and standardizing a stacking interconnection scheme which was bus-compatible with the PCI bus standard. Ampro still produces embedded PC products in the 21st century; it appears however the name "Ampro" may have been bought by another company.

My board

Ampro Little Board
A13001 rev A 1983
ROM is A75501-302

The floppy controller chip is a Western Digital 1770AH; there's a Mostek SIO dual serial chip and Zilog CTC counter/timer chip. There's also a parallel port using an LS744 chip and some additional logic. 64K of memory consists of eight 64K X 1 DRAMs. There's also an Elpac- TDK CB-3811 package, that's a DC-DC converter .A later model of this board included a SCSI controller chip and SCSI interface, not on this board.

Software assistance to me

Thanks to Gene Buckle of He personally updated his site's collection of Ampro software to include disk images. This is Rev G disks, probably for the Little Board Plus (SCSI).

Also thanks to Hal Bower and his B/P BIOS work; his pages preserved by He apparently had Ampro files for B/P BIOS, Z/CPR and ZsDOS. In 2010 I understood he might upload them to his site "in the near future". In 2021 I don't see them in the archived Web pages. But "his" ZSDOS had some support for Ampro Little Board hardware.

Thanks to Dave Dunfield's disk imaging utilites and archive on the archive Web site.

In 2015 Mark Greybill contacted me about his Ampro LB, and described the DC-DC converter module. Thanks!


Here's the Ampro as I got it, inside the monitor.
A look at the board itself.
The diskettes were created using Dave Dunfield's IMD utility.
Here's my setup for my first boot with the new diskette.
The board, installed inside a former SCSI drive case, with two 360K 5.25" drives.
Screen showing directories of both drives and boot message.

Comments from Rick Lehrbaum

In 2012, the designer of the Little Board and a founder of Ampro, Rick Lehrbaum, contacted me about my Web page, and gave me some of his early microcomputing background history. - Herb

"[While] I'm commonly called the 'father of pc/104', in reality I was just the leader of the team that developed it and the key evangelist in creating and expanding the pc/104 consortium. So it's not fair to those others -- it was really Ampro which was the creator of pc/104, and I was co-founder (one of three equal co-founders)."

"I built a couple of S100 systems in 1980 timeframe, using California Computer Systems boards. Also, I designed a multibus floppy disk controller for Advanced Micro Computers (AMD's failed experiment) around 1980, using discrete component phase-locked-loops (don't ask!). Also designed a DIY 8080 microcomputer ("8080 Abie") with hex keypad and 7-segment LEDs for I/O and a ROM monitor I wrote in assembler, similar to a KIM 1 sort of design. I may write it up one of these days on I also designed a dual processor 8/16-bit microcomputer for Dynabyte, the "Monarch" in around 1982." - Rick Lehrbaum
[Ampro Little Board]

Rick and I corresponded a bit, and he said he'd get around to providing some early documents of the Little Board. The board on the top of the image, is a Rev A production Little Board from 1983.

"A photo of one of the prototypes of the original Ampro Little Board is attached. You can see a few diffs relative to the photo on your little board page, esp the addition of connectors at the right edge of the board and removal of the big reset button. also unique to the prototype was a series of holes for mounting LEDs along the left edge of the board. If memory serves, I designed those so they would show either data or address bits -- for entertainment value ;-)."

8080 Abie

In July 2019 I contacted Rick again, and he replied: "Good to hear from you! sorry I never got around to taking [more] photos of some of the old Ampro boards, but I'll have a look and see if I've got anything that might be of interest to you. Meanwhile, here's a recent post that harkens back to my 8080/z80 days. Cheers - Rick"

His blog's post is of his 1979 design of that 8080 "Abie". It's a nice hex keypad/display for the 8080 processor,. A pretty minimal but solid-looking design, to run the processor under manual control. There's no "cheats" to jam instructions on the 8080, or to mess with the clock. But it's clear to me the ROM monitor had to "handle" the hardware.

I asked Rick about the source-code: "... sadly I don't have a listing of the monitor code that I wrote (and had someone burn into a PROM for me). So I don't have a record how my monitor software actually operated."

About the "serial port" on the schematic: "There was no conventional serial port; instead, I bit-banged square-wave audio into a cheap tape recorder, in order to store code I had entered into RAM using the board's hexadecimal keypad. When I wanted to run the saved code later, I loaded it back into RAM via a small, hand-entered routine. I didn't have the luxury of extending my monitor ROM to include the additional code for storage and retrieval from tape." - Rick

On another Web page, I discuss how audio cassette recorders of the 1970's were used for program storage. It's still a subject of interest today, if only to recover software. Many microcomputers into the 1980's used audio cassettes for storage; and as cheap means to sell programs! - Herb
[Slaight Little Board]

Recovery work by Tom Slaight

In May-June 2021, Tom Slaight contacted me, about restoring his Ampro Little Board to operation. He decided to disassemble his V2 ROM; he made a number of runs. He had or obtained a manual and a schematic, which he copied for me. Here's the Little Board schematic. A PDF of the manual is available from me as a PDF; ask me for details. Tom also repaired his Tandon TM-100-2A drives, some problems with track 00 sensors and slipping head mechs. Tom's gathered some Ampro disk-images (different revisions) to recreate the Ampro program disks, and reports the results below.

Apparently, the BIOS revisions for the Little Board (not SCSI, not Plus) are B, E and F; and rev G for the LB Plus:

Rev    P/N on diskette             identifier file on disk    CP/M bios version       CP/M Size
B        A60014 G (assumed)    none                         "20 February 84"      "61K"
E        A60014 E (assumed)    A60014.E                     "BIOS Version 1.3"    "61K"
F        A60014 F (confirmed)  A60014.F (Tom's disk)        "BIOS Version 1.4"    "61K"
G (LB+)  A60101 G (assumed)    A60101.G                     "BIOS Version 3.8"    "60K" 

Here's Tom's -F disk image. I reference others below. In mid-July 2021, Tom says "here's my final [result] of reverse engineered Little Board A75501-302 V2 boot ROM 8080 source code" It was assembled with CP/M ASM.

Other Ampro disk images

In May 2021 I was contacted by Tom Slaight, who asked about more Ampro code and docs and ROMS. I looked around the Web and here's what else I found. I tried to avoid the Ampro 8086 IBM-PC-oid versions. - Herb   
- lbsys-b.td0       69572  SSDD    Little Board system disk rev B
- lbsys-e.td0       81942  SSDD    Little Board system - enhanced rev E
- lb-cpm-g.td0     176326  DSDD    Little Board/LB+ system disk - Rev G for LB Plus
- and many many other files and disk images (some programs) (some LB Plus programs)
-- this has a software users manual for I think the non-Plus Z80 system, and soft/hard manuals for the Plus system
- Ampro stuff under ZNODE3 from Jay Sage
- From Don Maslin's archive: a pile of PROMS among which are "ampro boot ROM v2.0" . There's an "Ampro SCSI Boot ROM v 1.2"
which is for the Little Board Plus which has a SCSI controller on it. 

lbbootv2.rom        464  ROM     AMPRO Boot ROM v 2.0 
lbscsi12.rom       4096  ROM     AMPRO SCSI Boot ROM v 1.2

Note how small the boot ROM is. Probably, all it does is boot up the floppy disk/drive.

A MAME (ancient computer emulator) related Web site appears to say the "Little Z80 Board" from Ampro, is emulated under MAME. The apparent driver is "ampro.cpp". Apparent work was done in 2013 in MESS 0.150, and merged into MAME some time later.
- apparently someone named C.R.Bryan III ran RBBS 4.1 on an Ampro Little Board no SCSI. Compiled in BDS C for CP/M.

- add a 1MB RAM disk by an adapter board plugged into the Z80 socket. It has an I/O decoder to "bank" the pile of 256K DRAMS; and some helper for the Z80 refresh signal to cover a full 256 address range. Today one would likely use SRAMs. The following issue of TCJ has the software. 

Fun stuff with disk drives, by Tom

Aligning the Tandon drives was a pretty easy process using ImageDisk once I figured out what was causing an issue with ImageDisk. The first drive I tried would align but it would only stay in alignment for a while and then it would be out again. I saw the same problem before I tried to align the drive. Sometimes it would read, sometimes not. It turned out that the clamp on stepper motor shaft wasn't tight and would slip a bit. After I tightened up the hex screw it aligned just fine and stayed in alignment.

The second drive was also a bit loose so I tightened it up before doing the alignment. This time the alignment went fine on the first try. I shut down the PC; when I restarted it and ran the ImageDisk alignment again I got nothing. After trying stepping in and out with the utility I found the tracks were in alignment but reporting higher track numbers than they should have. After a few restarts I noticed that the shuttle was not being returned to 0 when the PC started up and if I manually set the shuttle to 0 everything would be fine, but if it was not at track 0 the PC would step it in on restart, but it wouldn't step back out to 0.

After a bit of head scratching I came up with the hypothesis that the problem was that the Track 0 signal was always asserted and indeed that was the case. Apparently both my PC's BIOS and ImageDisk only check for Track 0 "once" [at startup] and after seeing it assumed that they could just count steps in and out to monitor the track number and never checked the Track 0 state again. On startup my PC's BIOS steps IN a bunch and then when it goes to step OUT it checks Track 0 and immediately figured it was done. ImageDisk would then be handed a drive that was reporting it was at Track 0 but was actually stepped in and would go from there.

The track 0 circuit on the Tandon is interesting; The N.O. closure on the Track 0 microswitch is used to SET a Set/Reset flip-flop circuit by connecting it to ground while the used to RESET it. The SET was working but the RESET was not.

The fix was cleaning the contacts on the connector for the switch (J4), forcing some contact cleaner into the microswitch, and removing and reinstalling the screw holding the switch to make sure it was getting a good ground (the microswitch grounds through the drive chassis). After doing that everthing was working fine. With some judicious cleaning and lubrication both drives are working like new. Probably better than new, since based on my old disk copies it looks like one of the drives was out of alignment when I got it in '85. - Tom Slaight

Other Web links

There are many Z80 microcomputer supporting Web sites, and many Web sites for Z80-based operating systems including CP/M and derivatives. Search those sites for Ampro software and hardware documents and related products. has some Ampro LB Plus (SCSI) manuals.Also check their CP/M CD-ROM files (the "Walnut Creek CP/M CD-ROM") for Ampro related software. Other Web sites have that CD-ROM file set as well.

The "armory" Web site has some Ampro info including images of Ampro ROMs.

In Sept 2010, I was contacted by Larry Kraemer who successfully replaced 5.25-inch drives with 3.5" TEAC FD-235 Drives.. He gave me a fair amount of documentation, but here's the PDF of how he adapted 3.5" drives to a TRS-80 and a Ampro Little Board Z80 system. Contact me for more docs or to contact Larry. - Herb

contact me via email links at this linked Web page.

Copyright © 2021 Herb Johnson