CPM Kaypros

Kaypro Computer History by Phil Clayton

CPM Models

Kaypro Origin Stories

Lucy (81-110 Motherboard)

Kaycomp Machines

Kaypro II No Model Number

Kaypro II or 2 (81-003)

Kaypro 4 (81-004 & 81-006)

Kaypro 10 (81-005)

Kaypro 2 '84 (81-014)

Kaypro 4 '84 (81-015)

Kaypro 2X (81-014, 81-025, 81-033)

Kaypro New 2 (81-031)

Robie (81-012 & 81-013)

Kaypro 4X (81-015 Stickered 4X)

Kaypro 1 (81-021)

*Kaypro Business Paks

Theory of Operations

The Theory of Operations from Micro Cornucopia

Hardware

Hardware

"As of the first of October [1983], Kaypro has been soldering in all the small ICs."
(Micro Cornucopia, Oct 1983)

Modified Kaypro/Kaypros used as part of a system

Omni Logic Analyzer

K20

Kaypro 22 or 34

DK Synergy

CPM Compatibility Problems

CPM 2.2 ul compatibility

References to Problems with Possible Fixes

Drive Issues
"(Editor's note: Kaypro got a huge batch of flaky SMC data separators, and for several months, many systems were dying before they could get off the dealers' shelves. I assume that Ralph's system got one of the flaky chips. His next problem will probably be with the Tandon drives, but replacement with good quality half-wide Japanese drives is easy and quite inexpensive.)"
(Micro Cornucopia, Apr-May 1985)

Garbage Characters
Michael Stocker called recently to say that he had finally rid his screen of occasional garbage characters (even when using the Pro-884 Max in fast video mode). He simply replaced the 6116 static RAM chips in the video section with faster (150ns) parts.

He said he had gotten his new 6116s from Microprocessors Unlimited for $1.00 each (the video section holds two). The chips are located at U15 and U23 on the 84 Kaypro 1, 2, and 4.
(Micro Cornucopia, Feb-Mar 1986)

Kaypro Clock
I recently had to have my Kaypro 4-84 operated on. Turns out the power supply was sending occasional power spikes. With that replaced, all is fine again. I recommend Xerox Service (at least the Rochester, New York, branch still knows CP/M machines - they were discharging an Osborne when the Kaypro and I arrived).

The only problem was after servicing the machine when I used QP/M and got the message "Bad Clock?" It seemed to keep time okay after I reset it. I played with it for a day, but the message came up with each QP/M cold boot.

I don't know what made me think of it but I tried a program supplied with the machine - the graphic clock display in MBASIC. I have always thought it was pretty, but slow and not very useful. Haven't used it in over a year.

When I ran the Kaypro clock program, it asked if I wanted to set the clock. I said no because the clock was displaying the correct time with other programs. Then it said, "Clock not initialized ... , Enter new value:" and I said YES. It paused a moment and then asked for the time to set the clock. When I next cold booted with QP/M, all was fine.

I suggest that after any internal hardware work on a Kaypro with a clock, the Kaypro clock program should be run. That may solve other people's clock problems. My other suggestion is to buy QP/M. After getting QP/M the clock keeps good time - before, it lost a few minutes a week.
(Micro Cornucopia, May-June 1989)

Drive error - bad sectors
I use an old Kaypro 11-83 as a Z80 and Z8601 development system. I installed double-sided drives and the Pro 8 monitor ROM in 1984; the monitor version was 2.2.

After a longer than average programming effort, the B drive started generating bad-sector errors. Formatting and disk exercising programs confirmed that all tracks beyond number 40 had bad sectors. After opening the case, my eagle-eyed son noted that the B drive was double-stepping when it should have been single-stepping. A call to Micro C got a new monitor ROM on the way and some suggested tests to perform.

At this point, the Kaypro II was apparently fully operational, but it could not read the last 40 tracks on drive B. Normally, on warm boot, both drives were read by the monitor ROM and set to the appropriate drive configuration. Drive B should have been set for DSDD disks on a DSDD drive. However, the ROM assumed it had DSDD disks in a quad drive. This was the reason that it double-stepped when formatting. When the machine was forced to look at drive B by asking for its directory, it then recognized the drive as DSDD and the system worked fine.

The initial cause for the problem was thought to be the monitor ROM and it was replaced with a newer version (3.3). However, then the system would not boot at all. The old ROM was reinstalled and a new cause was sought.

U49, an 8-bit buffer (74LS241) that fed low order addressing to the monitor ROM, was checkpd; found to be good, and replaced anyway. The problem was solved.

Evidently, the LS241 had weakened over time and the monitor ROM was getting the wrong addressing information. The LS241 still appeared to be working, but not well enough to properly address the ROM. The monitor simply bypassed part of its own code and went merrily on its way.

So, if this problem ever comes up again, or if your system ever has problems booting, check U49 carefully. Try swapping it with U62 (another LS241). At $1 each (or less), you might want to replace both.
(Micro Cornucopia, July-Aug 1989)

End of CP/M machines

Kaypro announced its decision to discontine manufacturing and marketing the CP/M line in November 1987 in order to "focus its sales and marketing efforts on a smaller group of mainstream technology computers."

The announcment also stated, "The company will continue to provide technical support and will maintain available spare parts to support out-of-warranty needs of [CP/M] end users."

Although there frankly are not a whole lot of Kaypro dealers who still service CP/M Kaypros, the ones who do are quite commited to the CP/M user.
(Profiles, July 1988)