Mainboard 81-240: Difference between revisions
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==Mods for this board== | ==Mods for this board== | ||
===Upgrading to a "Kaypro 8"=== | |||
Upgrade a 4 to an 8. This is a reference to making it work with the Pro 8 ROM form Micro Cornucopia due to it working with the Quad Density Floppy Drives (close to 800 KB per disk). | |||
Found on page 14 of the December 1983 Micro Cornucopia. Click [https://bitsavers.org/magazines/Micro_Cornucopia/Micro_Cornucopia_15_Dec83.pdf here]. | |||
===256K upgrade=== | |||
On page 44 of the June-July edition of Micro Cornucopia there is an article about upgrading this motherboard to work with 256K. If your machine has an additional board with a 74LS393, 74LS158 and 74LS153 plus the 8 RAM chips have been replaced by 64K RAM chips then you likely have this mod. Click here for this [https://bitsavers.org/magazines/Micro_Cornucopia/Micro_Cornucopia_30_Jun86.pdf Micro C] | On page 44 of the June-July edition of Micro Cornucopia there is an article about upgrading this motherboard to work with 256K. If your machine has an additional board with a 74LS393, 74LS158 and 74LS153 plus the 8 RAM chips have been replaced by 64K RAM chips then you likely have this mod. Click here for this [https://bitsavers.org/magazines/Micro_Cornucopia/Micro_Cornucopia_30_Jun86.pdf Micro C] | ||
==Problems with solutions== | |||
===Drive issues with speed up boards=== | |||
<blockquote> | |||
I have a Kaypro 4 late '83 or early '84 model, 81-240A board with some chips soldered. ... | |||
The speedup kit ... it has done strange things to some disks, corrupting files with chunks of other files. Apparently, it changed the file allocation blocks in the directory tracks. ... | |||
I hope you did the CAS-MUX mod when you speeded up the system. If you didn't (many people don't), I'd do that immediately (see the Kaypro column in this issue, or see Issue #12). If your system runs OK for a while at 5MHz and starts making trouble, then it's probably a heat sensitive chip.<br> | |||
(Micro Cornucopia, Feb-Mar 1986) | |||
</blockquote> | |||
Latest revision as of 18:42, 29 October 2026
81-240A General Info
The 81-240A Mainboard was used for both the Kaypro II '83 and Kaypro 4 '83 machines. According to reports it detected if it was reading a single or double sided drive and would continue to function based on that data.
The previous board for the Kaypro II was the 81-110.
The universal board would replace it for the K2 '84 and K4 '84.
While the Q1 and it's resistor are silk screened on the board I have not seen them used on the 81-240. See the notes in Mainboard 81-110#Q1 for what this does.
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81-240A Machines
| Serial Num | Board Num | QC Sticker | Monitor ROM | Char ROM | Kaypro Model | Notes |
|---|---|---|---|---|---|---|
| #16679 | 30484 | none | 81-232 | 81-146 | KII No Model Num | Likely a FrankenKaypro due to multiple parts from multiple eras. Shield |
| #17083 | 53883 | M-681? | 81-232 | 81-146 | KII No Model Num | FrankenKaypro? Shield |
| #69691 | 14084 | 189-W | 81-232A | 81-146A | K4 81-004 | Shield |
| #76797 | 21658 | NLS FT 51? | 81-232A | 81-146A | KII 81-003 | Shield |
| #102622 | 20433 | 162-W | 81-232 | 81-146A | KII 81-003 | Shield |
| Loose board | 2980 | 81-232 | "CHAR V2.2 1992 D. Th? | |||
| Loose board | 29566 | 81-232A | 81-146A | Shield | ||
| Loose board | 29682 | 81-232 | 81-146 | Shield |
Mods for this board
Upgrading to a "Kaypro 8"
Upgrade a 4 to an 8. This is a reference to making it work with the Pro 8 ROM form Micro Cornucopia due to it working with the Quad Density Floppy Drives (close to 800 KB per disk).
Found on page 14 of the December 1983 Micro Cornucopia. Click here.
256K upgrade
On page 44 of the June-July edition of Micro Cornucopia there is an article about upgrading this motherboard to work with 256K. If your machine has an additional board with a 74LS393, 74LS158 and 74LS153 plus the 8 RAM chips have been replaced by 64K RAM chips then you likely have this mod. Click here for this Micro C
Problems with solutions
Drive issues with speed up boards
I have a Kaypro 4 late '83 or early '84 model, 81-240A board with some chips soldered. ...
The speedup kit ... it has done strange things to some disks, corrupting files with chunks of other files. Apparently, it changed the file allocation blocks in the directory tracks. ...
I hope you did the CAS-MUX mod when you speeded up the system. If you didn't (many people don't), I'd do that immediately (see the Kaypro column in this issue, or see Issue #12). If your system runs OK for a while at 5MHz and starts making trouble, then it's probably a heat sensitive chip.
(Micro Cornucopia, Feb-Mar 1986)