Skip navigation

There is surprisingly little information floating on the net about the Kaypro PC as it’s generically called. This can be pretty surprising since if you’re into retro computers Kaypro was a pretty major player in the 80’s and is best known for their line of luggable CP/M machines like the Kaypro 10 which I glanced over in an earlier article. As the 80’s moved on CP/M was becoming less and less relevant as the world was being conquered by the might of the MS-DOS IBM compatibles. Kaypro, late in the game, finally decided to release a DOS IBM clone of their own around 1985 and thus we received the Kaypro PC or as my PC is badged, the Kaypro EXP.

The dual floppy drives on the right are dual 5 1/4 inch 360k drives.

On the left side of the case is the case badge along with a recessed section with a power and HDD activity LED.

The Kaypro PC, like many early PC’s, has a large power switch on the side and at the rear of the case.

The power supply itself is a 135w PSU from Phihong Enterprises, whom I’ve never heard of before but that should be enough juice to safely add a hard drive without issue.

Now let’s take a look on the back of the Kaypro EXP.

The Kaypro PC sports a power plug for a monitor to save some space on your wall outlet or power strip. There are eight slots for expansion cards as well as a PC keyboard connector. This is a PC keyboard connector and not AT so make sure if you don’t have the official keyboard that your keyboard is PC compatible or has the ability to switch between PC/AT compatibility.

Looking carefully you may notice the card all the way to the right is a little unusual. Originally I thought the card on the far right may have been an accelerator card but for the Kaypro PC, this isn’t the case. We will take a much closer look at this card when we get inside the case.

With the case open we can see various cards as well as the bays for the two floppy drives and an adjacent bay for a hard drive. My Kaypro EXP did not come with a hard drive installed but other models did have a 20MB and then 40MB option.

Attached to the side of the case is a real PC speaker as opposed to a piezo type speaker.

Now let’s remove the various expansion cards and take a better look at the motherboard itself.

This slideshow requires JavaScript.

 

Unlike the overwhelming majority of IBM compatibles of the time the bulk of the major PC components on the Kaypro PC come on a single interface card as opposed to the motherboard itself. This card contains the CPU as well as the chipset. The idea was that this layout was more convenient to the end user and when it came time to upgrade rather than buying a whole new motherboard and case and then transferring all previous cards you had over you could simply replace one card in the case and be done with it. It seems like a pretty good idea at first but the concept didn’t really catch on as PC technology moved faster then Kaypro probably anticipated which required changes more significant than a simple card swap. You can see this thinking in the image above as the “motherboard” has two 16 bit ISA slots even though as we will see the CPU on the main card is only 8-bit. Kaypro did make a 16-bit 286 CPU card as well as a 386 card.

It looks like the board has provisions to easily add more 16-bit slots in future productions. My guess is that the 286 Kaypro PCs likely came stock with a “motherboard” that contained more 16-bit slots.

Other then the ISA slots the board is extremely sparse and only has a few capacitors as well as the unidentified gray block you can see at the top in the image above. There is also a standard AT PSU connector and two other four pin auxiliary power connectors. I have no idea what these extra power connectors are for but maybe they were a way to add more power if needed on future revisions of the board.

My Kaypro EXP did not come with a hard drive or for that matter a hard drive controller card but it did come with a separate floppy drive controller card for the dual 5 1/4 inch 360kb drives.

My EXP also came with a rather large serial and parallel port controller card as seen below.

The video card in my Kaypro EXP was an ATI EGA Wonder 800 with 256kb of DRAM. The EGA Wonder 800 card also supports extended EGA text and graphics modes as well as 16 color VGA modes. For convenience I replaced my EGA Wonder card with an 8-bit VGA card.

None of the RAM for the Kaypro PC is installed on the main board but comes on its own RAM card.

Unfortunately, my Kaypro PC only came with 256kb of memory through the card itself can be expanded to a total of 768kb. Most 8088 based PC’s of the time were limited to 640kb of RAM within the first megabyte but the Kaypro PC could address an additional 128kb. I’m unsure if this extra memory could be fully utilized the same as the other 640kb or if it was only able to be used as a RAM drive.

Finally, we have the full length “CPU card” which hosts the CPU itself as well as the other vital chips for operation.

near the front of the card is the CPU as well as a socket to add a math co processor. My card came with an NEC V20 chip installed. The V20 was a common upgrade for 8088 based PC’s of the day and was a faster pin-compatible replacement for the 8088. I am unsure if the NEC V20 is factory stock or if someone replaced the original 8088 CPU though I’m inclined to believe the V20 came stock as most sources I’ve read claim the 8088 Kaypro PC was faster then most competitors of the time.

Rear of card

 

Front of card

 

Back of card

On the external plate the card has a small red button as well as a switch. The button is used to quickly reset the system while the switch sets the CPU speed and acts as a turbo switch. I couldn’t run any diagnostic programs to determine CPU speed due to the lack of RAM in my machine but after playing a few speed sensitive games on it I believe the speeds are likely 4.77Mhz and 7.16Mhz.

The Kaypro PC was late to the IBM compatibles market but when it did arrive it had a very interesting concept. It’s worth noting Kaypro wasn’t the only company to experiment with the “computer on a card” idea at this time but it is one of the most notable examples. When you think about it it’s an interesting idea and would allow a really easy and in theory cheaper upgrade path but computer technology was just moving too fast and motherboards just evolved to quickly for the concept in those days.

4 Comments

  1. Nice to see!

    I think the grey block is a power resistor, probably there to apply load to the power supply if there are no cards installed. (no load can adversely affect earlier PSUs).

    I know it’s unlikely to cause an issue, but I’d put a sticker of some sort on that EPROM window so it doesn’t get erased over time.

    – Sparcie

  2. Good call on the EPROM. I will next time I’m in there.

  3. Old tech like this is amazing. So nostalgic! The in-depth presentation really shows how much you enjoy these machines.

  4. I managed 3 Kaypro PC’s for a company in the 80’s. A few thoughts…
    They came with the V20 processors. (Very sure of this.)
    Ours had the memory on a longer card – maybe a IO/memory/Floppy combo card.
    The company claimed they could be upgraded to 286 processors, but our backplanes only had 8-bit slots.
    The extra 128K of memory can be disabled or mapped in the upper memory region (between 640K and 1M) using the DIP switches.
    I wrote a couple of asm utilities for the extra memory. The first program allowed MS-DOS to use the extra memory by linking it into DOS’s memory chain. The second allowed loading network drivers into the extra memory.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

FDISKformat

A place for the pc collector

I ❤ Old Games!

Probabilmente il miglior blog bilingue al mondo*

Waltorious Writes About Games

Game-related ramblings.

NekoJonez's Gaming Blog

My Gaming Timeline

Evelynn Star

Lynn talks about video games, records and books ...

Retro Megabit

Sharing My Retro Video Game Collection.

133MHz's Junk Box

Random electronics and gaming crap

SNES A Day

Chronogaming project featuring reviews, screenshots, and videos of the entire Super Nintendo library in release order.

Retrocosm's Vintage Computing, Tech & Scale RC Blog

Random mutterings on retro computing, old technology, some new, plus radio controlled scale modelling.

The PewPew Diaries.

Work(s) in Progress!

1001Up

1001 video games and beyond

retro computing and gaming plus a little more

sparcie

retro computers and stuff

jispylicious

Stay Jispy!

%d bloggers like this: