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Ever feel like 5 slots just isn't enough?

maxtherabbit

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Apr 23, 2019
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I sure did, built this lo-tech EMS card and didn't even have a slot in my 5150 to shove it in. Just so happens my clone FDC had one of those semi-common but apparently useless 62-pin footprints for a pin header right about the edge connector. Let's put it to use!

Drew up a super quick adapter PCB and grabbed a 62-pin card slot and right angled pin header from digikey, and I present to you: a 6 slot 5150.

20190906_123409.jpg20190906_123419.jpg20190906_123429.jpg20190906_133203.jpg
 
Nice! Works well with those extra-wide slots on a 5150, too! I definitely run out of slots in the 5150, part of the reason I don't usually have one set up and running. Memory expansion, floppy controller, disk controller, video card...then one slot left for usually a serial/parallel combo board. If you want a NIC you have to pull one or use a Xircom or SLIP/PLIP.

You could certainly see why stuff like the SixPak Premium (memory expansion, EMS, clock/calendar, serial, parallel, game) and Dallas SmartWatch modules were popular!
 
What about a riser card for those shorter cards that don't have external ports?

that would be cool, but out of the 2 cards I have with no external ports, only the lo-tech EMS would have been short enough to clear the HDDs

I was already pushing the limits of physical space with my WD1002S-WX2 and the rear slot bracket for my parallel and game port sharing slot 5

(risers are starting to become hard to find too, and expensive)
 
It's amusing how close those pins are to a Tandy Plus Bus header.

Back in the day was someone actually selling machines that used those holes to run a stack of ISA cards vertically? (IE, fitting each card with solder-tail-type female connectors so they could be plugged into a pile?) I do vaguely remember seeing those hole patterns on a few cards.
 
Good thinking, I've seen those hole patterns too on other cards but never put any thought into them other than maybe test points, I probably have some cards stashed away with the same.
 
I've always been interested in how they reached the design decisions to:

A) Integrate almost nothing onto the motherboard, providing only a keyboard interface and a cassette interface which no one used. When I suspect over 99% of 5150s shipped with at least one floppy drive, what possible reason is there to have the floppy controller on a card and not just have it integrated into the board? Ditto for a parallel/serial port when I can't see many being used for real work back in the day without a printer connected yet no means of connecting one is built in.
B) Given A), to only then provide 5 card slots. How on earth would this ever have been considered adequate? If you use genuine IBM parts, a relatively basic setup with floppy drives, CGA, one parallel port, one serial port and a memory expansion maxes out the system leaving no possibility to expand it further. It was only the existance of third party products integrating more than one thing on a single card which made 5 slots viable to work with.
 
The 5 slot design allows the IBM PC to match the full load out for the System/23: MDA + Parallel port, disk drive adapter, and 3 memory cards bringing the system to 256 kB. CGA was for gamers who weren't expected to print; IBM made the same decision to exclude parallel port from the base PCJr even though, by then, it was obvious that printers mattered.
 
It's amusing how close those pins are to a Tandy Plus Bus header.

Back in the day was someone actually selling machines that used those holes to run a stack of ISA cards vertically? (IE, fitting each card with solder-tail-type female connectors so they could be plugged into a pile?) I do vaguely remember seeing those hole patterns on a few cards.
Apparently, some of those early Tandy ISA cards (for the 1000 and 1000A specifically, I think) DID have a PLUS header in that exact spot. It was for reusing an EX/HX PLUS card in an ISA system, which, IMO, is next to useless, since PLUS cards are so hard to come by. Looks like you've just found a use for it!

I suppose, back in the day, you could have used that header to expand a 3-slot Tandy 1000 system to a psudo 4-slot using a PLUS card. I THINK that's what they were intended for.
 
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I've always been interested in how they reached the design decisions to:

A) Integrate almost nothing onto the motherboard, providing only a keyboard interface and a cassette interface which no one used. When I suspect over 99% of 5150s shipped with at least one floppy drive, what possible reason is there to have the floppy controller on a card and not just have it integrated into the board? Ditto for a parallel/serial port when I can't see many being used for real work back in the day without a printer connected yet no means of connecting one is built in.
B) Given A), to only then provide 5 card slots. How on earth would this ever have been considered adequate? If you use genuine IBM parts, a relatively basic setup with floppy drives, CGA, one parallel port, one serial port and a memory expansion maxes out the system leaving no possibility to expand it further. It was only the existance of third party products integrating more than one thing on a single card which made 5 slots viable to work with.

Tandy learned from IBM's mistakes, and integrated all the essentials onto the MB. That's why the Tandy 1000 line did so well. :smile:
 
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I think 5 slots was just fine for an early 1980's PC machine. Once the PC caught on and people started making other types of cards for it then switching to more (and 16 bit ) slots made sense.

IBM had a price point to reach and installing items on the motherboard would raise that price too much. Besides IBM liked charging some money for upgrades and probably wasn't expecting the demand they got for the units (and 3rd part interest in making cards for them).

Who purchased a 5150 to game on anyway (before there were even sound cards made for a PC that would need a slot)?
 
Five slots isn't great in the context of the original option card selection for the 5150, but when third-party companies started churning out those combo cards that had 384k (or 576k), parallel, serial, and clock (and sometimes FDC) functions on them it starts to look more reasonable. My "toy" maxed-out 5150 that I slapped together in the early 90's had one of those cards, VGA, and a hard disk in it and thus still had two slots to spare.
 
Five slots isn't great in the context of the original option card selection for the 5150, but when third-party companies started churning out those combo cards that had 384k (or 576k), parallel, serial, and clock (and sometimes FDC) functions on them it starts to look more reasonable. My "toy" maxed-out 5150 that I slapped together in the early 90's had one of those cards, VGA, and a hard disk in it and thus still had two slots to spare.

You still got that toy? I had a 5150 around then, but foolishly got rid of it.
 
You still got that toy? I had a 5150 around then, but foolishly got rid of it.

Nope. Only machines I still have from back that far are my TRS-80 models I, 4, and 4P. (And it's kind of random luck that I was able to hold onto them.) Old IBM PCs were still pretty literally worthless back when I needed to purge. (TRS-80s probably were too, but I had an intuition that they'd be harder to replace, so they ended up in storage.)
 
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