IBM 5150 secondary storage

[defiant1dave]

Being the somewhat odd and semi-curmudgeonous person that I am, I oftentimes undertake computer projects that have no real usefullness other than to see if it can be done. If the same energy were applied to truly useful things, I'm sure I'd be wealthy...... but hey! It's a character flaw....

Right now, I'm exploring the true operational limits of the IBM 5150 of 1981 vintage. I've had several of these beasts collecting dust for many years, and have decided to find out exactly what they can accomplish. Sure, we might laugh at how slow such a machine is by today's standards..... but their logic is sound, and they are reliable as all hell. In theory, if programmed correctly using structured sub-modules, one should be able to accomplish any task that we can think up...... at it's own liesurely pace.

I have a very early (first bios date) PC which I've chosen to be the test- unit. Since it's bios cannot recognize UART Chips or any type of HDD controler, I'm stuck using either floppies or the cassette interface. ... and since floppies would be far too limited in their capacity, I've decided that a tape drive, or perhaps a large reel-to reel recorder of late 70's vintage is to be used for secondary storeage.

The problem is that I can't find any documentation on the pin-outs for the IBM Cassette port on the back of the 5150. I've got the original service manual and the operations manual for this unit, and neither one has this information.... nor does any IBM technical person that I can find. I have also been unable to locate any original PC to Cassette cables, or any IBM intructions on using a recorder. I am beginning to wonder if IBM actually intended for this port to ever be used...... perhaps it's just a "teaser".

Anyway..... that's what i'm working on at the moment. If anybody has the information I need, it would be greatly apreciated.

[Jark]

Strange you say that the Bios cannot recognize any HDD... I have used a genuine 5150 from 1989 to 1992, that I had customised with a 20 Mb HD, some RAM and a Hercules clone. So I had something like a poor XT...

Probably my machine was more "recent" than yours : as far as I can remember, there was something like 128 kbytes of original RAM. No graphic card, double 5 1/4 drive : the machine was used as a sortoff passive terminal in a IBM token ring network.

G basic was hardcoded in the ROM... so that you could prog if you did not insert a Dos bootable floppy!

[defiant1dave]

The vast majority of 5150's were made after IBM recognized their error, and had bios's that would work with hard-drives. A very few however, were made during late '81, and early '82...... and these machines had bios's that would not recognize HDD's.

Then again..... that's the reason I picked it! Since the entire thing is just an academic exercise, I wanted a bit of a challenge. I had considered a 5140 as a basis........ but they are REALLY ignorant!

By the way, I found the pin-outs..... they are the same as a Radio Shack TRS-80 of the same vintage.

[Jark]

I thought 5150 was the first PC... What was it made of ?

I also worked with a Sinclair Z80, my father still has it. That was amazing because it had graphics features. The most funny was storage on a tape recorder...

[SCM]

Jark wrote:

The most funny was storage on a tape recorder...

I had a Timex Sinclair. The very small memory and tape storage were a pain, but I learned a lot from it. Now what was that you were going to do DD (I'd use Dave, but that's already taken).

[defiant1dave]

Jark wrote:

I thought the 5150 was the first PC.....

Yes the 5150 was the first "PC".... The term PC refers to "Personal Computer" which is a term that IBM coined for it. It was not however the first microcomputer..... quite a number of small computers came before it, even a couple of IBMs. The 5100 preceded it by a solid five years. What the 5150 did was to start a dominant branch in the evolutionary line that led to our current computers.

[defiant1dave]

This project is coming along quite nicely..... but I've posted the update in the "General" category since it is actually a "Cassette Basic" project, and not QBASIC.

[na_th_an]

[off-topic]Sinclair ZX Spectrum was an amazing machine, released in 1982. I still code for it . There is a great community here: http://www.worldofspectrum.org

Timex Sinclair 20xx is just the american clone.[/off-topic]

[peace]

The first true micro-computer was the Apple 2.
Even the earlies Apple 2s can use a hard drive with the proper cords though early ones couldn't use it for booting.
The 2+ and 2E both could use hard drives are bootup.
Before Apple 1 and other computers prior used leds and jumpers to program.