Tandy 600 and Zenith ZP150
Twins or just distant cousins?  You decide...

What I've done here is put the  Tandy 600 in one column and the Zenith ZP-150 in the other column so you can compare side by side.

My observations are this.  They share a common heritage.  Both utilize the 80C88.  It would appear, at least to me, that the Zenith is the first shot and the 600 the more "commercial" revision.

Both units utilize OKI parts.  Okay, big deal, but with OKI markings on the motherboards and a lot of OKI chips, it does infer a relationship.

Both utilize Microsoft Works as the "Operating System."  The Zenith came with ver 1.10 and the 600 1.20.  The Zenith does one thing better here, the BASIC is included without having to shut down and swap out a chip.  With the 600, you have to completely remove the Works ROM.  To me, that doesn't make any sense at all.  Maybe Radio Shack in their infinite wisdom decided most people wouldn't want the BASIC and decided to make a little cash on it and sell it as an option, a $130 option!

The 600, obviously, has an advantage with the inclusion of a 3.5" floppy drive.  This is purportedly the first time a 3.5" drive was included in a laptop.  The truly annoying thing about the floppy is the format program is in BASIC!  Yeah, you have to buy the BASIC option in order to format diskettes!  Does that make sense to anybody?  It sure doesn't to me!

The Zenith has about double the RAM, 416K to the 600's 220K, when fully expanded.  Why the reduction on the "later" version?  Beats the heck out of me, unless it was to reduce cost and, again, make a little money on the expansion RAM modules.

Minor, but annoying, differences include:
1.  The 600's internal batteries.  Wish they'd kept the AA option of the ZP.  Much easier to deal with.

2.  It's also a LOT easier to swap out ROM cartridges and even add more ROM's on the Zenith unit.  Slide off the battery cover and pop them in.  On the 600, you have to flip it over, and pop a cover, similar to the Tandy 100/102/200 series.  Guess Radio Shack liked that idea better.

3.  There's no volume control on the 600.  No biggie, but still an interesting deletion.

4.  Built in internal modem on the Zenith!  I have no idea what speed, but guessing 300 baud.  Yes, Henry, they actually made modems that slow in the "olden" days!

My conclusion is that the Zenith came first, with the Tandy coming within a year later.  So are they related?  I think so.  Sort of a older brother Zenith, baby brother Tandy.

Just got in a copy of Portable Computer Review, Vol. 1, No. 2, Fall/Winter 1987, page 26.  According to this magazine, the Tandy 600 was never meant to be offered to the general public.  Rather, it was going to be sold on a commercial contract which fell through.  Tandy merchandising tried to make the 600 appear to be the next logical step in the progression of its laptops.  To me, this doesn't make much sense for the following reasons:

1.  Tandy isn't much on commercial contracts for non-standard items.  Heck, from my time with "The Shack," (to my knowledge) they never did a contract that would create an entirely new item and not offer it to the general public at a higher price.

2.  If they were to enter into a contract such as this, they would take an item that was either in the current line-up or about to be introduced and give the contractor one heck of a sweet deal on the price. 

This would explain why the 600 seemed to just appear out of nowhere and disappear into the same place so quickly and quietly.  But it doesn't sit well with the corporate climate of Radio Shack at the time.

If you would like to read the pertinent part of the article, here it is.

Which one is best?  In my opinion, neither.  I would like to have a 600 with the floppy drive and the Zenith's memory, batteries, and ROM options.
TANDY 600 Zenith ZP-150


The Zenith motherboard looks a lot busier.

I like the Zenith RAM upgrade a lot better.  Much tighter and neater looking.  They also don't have as much chance of working loose!

Tandy wins here.  Much nicer keyboard

Don't believe I have to say much here!!!

Okay, what's missing here???

Zenith wins here.  Lot easier to get to and more expandability.
Does anyone know what the dip switches are for?

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