Mainboard 81-110

81-110 General Info

The 81-110 Mainboard was the original Kaypro board and debuted with the first Kaypro II machines, including the Kaycomp machines. It's design was based on the Ferguson Big Board. (Thomas Brase)

It was exclusively used in the Kaypro II and for the most part was replaced by the 81-240 sometime in 1983.

Most of the oldest machines used the 81-110A board but an 81-110(no letter) board has appeared and appears to be the oldest known board.

The 81-110B, B1 and B2 represent a cost reduced version of the 81-110A board since they use fewer chips. It is likely that the 81-110B board had an issue since it was replaced very quickly making that board relatively rare.

Also note that the floppy controller chip was changed when they switched from the 81-110A to the 81-110B board.

Legand/Info:

• 81-149(C) = 81-149 C written in
• MC = MicroCornucopia
• Q1 = Q1 and C6 are present
• ROMs are as labeled

Repairs

In the December 1986 issue of Profiles a letter was sent in with the following statement: "... because Kaypro, under a new policy decision, will no longer send him [local dealer] any parts [for CP/M machines]".

The response: "Patricia Crabtree, manager of Kaypro Technical Support, says that there are parts available for Kaypro's CP/M machines and that they are shipped to delaers within 24 hours."

Patricia clarifies one point: "However, if you are a Kaypro 2'83 or 4'83 owner, and you have a problem with your main board, your dealer will have send your machine to the Solana Beach facility in California for repair. This is because these main boards are no longer being made and therefore cannot simply be replaced--they must be repaired."

Q1

The Q1 transistor and it's resistor were designed because "The Kaypro's mother, the Big board, had a 74LS04 in this spot. That part did not get close enough to + 5V for the Z80's clock, so a "pull up" transistor was added." (Micro Cornucopia, Apr-May 1986)

The fix was to upgrade to 74HCU04 which allowed the Q1 to be removed from the board but when a machine is upgraded from 2.5 to 5 MHz the HCU chip could cause timing issues and a 74HC04 should be used to replace it. (See Micro Cornucopia above for more details)

BIOS Changes

During the Spring of 83, Kaypro spent several months trying to clean up a disk error problem. During this period they went through three new versions of their monitor ROM. The monitor ROMs (U47) were marked (on the paper stuck on the ROM) with an 'N, 'B', or 'C' suffix. Kaypro shipped a few 'A' versions and almost none of the 'B' versions (I understand they had a bad bug), before they went to the 'C' versions which they are still shipping.

I hadn't been able to find anyone who could tell me what they changed from version to version, but now, thanks to a letter from Terry Kingrey, I have a pretty good clue.

Terry tried installing one of our PRO-monitor ROMs on his system but it didn't work (he hadn't told us that he had one of the 'A' ROMs). So he tried substituting parts on his Kaypro to see if he had a defective chip (we would have told him not to bother). He didn't have a 1797 floppy disk controller to swap with the one on his board so he substituted a 1793 from a friend's Kaypro. After he substituted in the 1793 he found that his system worked just fine with our PRO-monitor ROM.

That news sent Dana and I to the Western Digital book to see what the differences were between the 1793 and the 1797. The 1797 does side select and the 1793 doesn't, but Kaypro isn't using that line. However, the 1797 requires a sector size bit, the 1793 doesn't. That could be the difference.

Anyway, if you are one of the select few with an 'A' version of the Kaypro, it looks like you can upgrade to one of the PRO-monitors (II, 4, or 8) if you will replace your 1797 with a 1793 disk controller. ...

If you have a ROM with no suffix or with a 'C' suffix you are just fine. You have the 1793 disk controller already.
(Micro Cornucopia, April 1984)

Upgrading a Kaypro 2 to 4

See page 14 of the December 1983 Micro Cornucopia. Click here.

81-110

See Lucy for details.

Source: Stargeezerlabs

There is a possibility that there could have been an even earlier board according to a letter to the editor in the December 1982 Microcornucopia "They used 4164 RAMs, the keyboard outputs serial data to port B of the SIO, and they changed the 1771 to a 1791 for double density (5"). The board has space for the CTC timer and for all four EPROMs but there is a socket for monitor ROM only."

81-110 Machines

Serial Num	Board Num	QC Sticker	Monitor ROM	Char ROM	Notes
"Lucy" Label Missing (Version 2 small power switch and black handle covers would place it near #3200-3800)	1145	26JL82	No Label	D182	Drive Fix Mod Q1

81-110A

The 81-110A is notable for 4 unpopulated chips locations from the Ferguson Big Board design (CTC, Monitor ROM, and 2 74LS chips). It was proceeded by at lest one 81-110 in serial number.

81-110A Machines

Serial Num	Board Num	QC Sticker	Monitor ROM	Char ROM	Notes
#2767	1353	6-30-82 31 NLS	81-149	81-146	Q1
#2775	1457	30 Jn 82 29 NLS	81-149	81-146	Drive Fix Mod Q1
#3249	1588	16 Jl 1982 29 NLS	81-149(A)	81-146	Q1
#3590	2220	6 Au 1982 4 Aug 1982 NLS QA 115	?	?	Drive Fix Mode Monitor pin 21 -> U59 pin 2 U60 pin 1 ->pin 8 Speed up mod w/switch RTC board Q1
#4207	2997	"R" NLS 3	81-149	81-146	no mods Q1
#4307	2035	"R" NLS 3	81-149	81-146	Q1
#4222	3057	"R" NLS 3	81-149	81-146	no mods (Q1?)
#4223	3051	"R" NLS 3	81-149(C)	81-146	Drive Fix Mod (Q1?)
#4623	3621	"R" NLS 3	81-149	81-146	Q1

81-110B

The B board in extremely rare. It apparently had some technical problems that required the rapid update to the B1 board. It's design allowed for the total chips used to be reduced from 83 (A board) to 72 (B board).

Chips removed

Scroll Hardware

Chips U51, U52 and U53 were removed because they were for the Scroll Hardware that was never implemented from the Big Board.

81-110A

81-110B

They also removed the three ICs that handled the scroll in the video circuit. ...

They had to rewrite the monitor routines and the BIOS because of the changes. They had to support double density 5" drives and they had to handle screen scrolling in software. ...

Try using the Kaypro as a terminal and set the baud rate over 1200. Once the screen fills, it starts dropping characters each time the screen has to scroll. You see, the processor has to move every character in video memory during a scroll (which takes a while). Meanwhile, the Z80 ignores all about the characters - that are coming in the serial port.

With the hardware scroll, the video circuitry automatically shifts everything by one line and points the processor to the correct spot in video memory. The processor doesn't have to so much as raise an address line.
(Micro Cornucopia, Dec 1983)

"Actually, the very early Kaypro lIs had the hardware scroll circuit installed. They didn't use it because Gilbert Ohysnty couldn't figure out how to do the hardware scroll calculations in the monitor. Later, they removed the 3ICs because they weren't using them."
(Micro Cornucopia, Apr 1984)

81-110B Machines

Serial Num	Board Num	QC Sticker	Monitor ROM	Char ROM	Notes
#7872	5372	NLS 16 FT	MC K8 ProMonitor	MC Clean ProCHAR	CPU adapter board Drive Fix Mod U86 Pin 4 -> Pin 3 (board) adapter This board was swapped for #93481 since it is a rare board No Q1
#8098	5319	"R" NLS 3	81-149	81-146	Aurex drive card 3 chip video card Keyboard has been swapped so might be a "FrankenKaypro" No Q1
#27396	3772	"R" NLS 3 115-W	81-149(C)	81-146	Drive Fix Mod Q1

MC= MicroCornucopia

81-110B1

81-110B1 Machines

Serial Num	Board Num	QC Sticker	Monitor ROM	Char ROM	Notes
#7954	6992	NLS 16 FT	MC ProMonitor	MC Clean ProCHAR	Drive Fix Mod
#8409	6855	NLS 16 FT	81-149	81-146	No mods
#10126	9267	"R" NLS 3	81-149	81-146	No mods
#12275	15561	"R" NLS 3	81-149	81-146	No mods
#12654	11355	NLS 16 FT	81-149	81-146	Drive Fix Mod
#13480	26987	"R" NLS 84	81-149(C)	81-146A	Drive Fix Mod K2 81-003 Model
#15453	15852	"R" NLS 3	MC ProMonitor	81-146	Drive Fix Mod Speed mod 5V RCA out U52 Bypass
#16288	16001	"R" NLS 31	81-149	81-146	No mods
#21460	10729	"R" NLS 3	81-149	81-146	No mods
#23201	14858	162-W	81-149(C)	81-146	Drive Fix Mod
#24500	7373	"R" NLS 3	81-149(C)	81-146	Drive Fix Mod
#27336	27618	115-W	81-149(C)	81-146	Drive Fix Mod Shield
#43168	37841	"R" NLS 3	81-149(C)	81-146	Drive Fix Mod Shield KII 81-003
#43486	35399	115-W	81-149(C)	81-146	Drive Fix Mod Shield
#45618	44964	Round ?	81-149(C)	?	Drive Fix Mod Shield KII 81-003
#57145	50971	blank	81-149C	81-146	Drive Fix Mod Shield
Loose board	16392	"R" NLS 3	None	81-14?	Drive Fix Mod Speed up U66 Pin 3->4 (board) U66 Pin 4->5
Loose board	53659	NLS FT 31	?	(MC?) Greek ProChar	Significant Repairs

81-110B2

81-110B2 Machines

Serial Num	Board Num	QC Sticker	Monitor ROM	Char ROM	Notes
#20250	21132	162-W	81-149(C)	81-146	Drive Fix Mod
#27007	28342	Circle?	81-149	81-146	Drive Fix Mod Shield
#42891	40019	116-W	MC K8 ProMonitor	81-146	Drive Fix Mod 3 chip video card Monitor pin 21 -> U59 pin 2