IBM 5100 book



#24

The recent forum discussion of the IBM 5100 made me look in the book that, I believe, was the "bible" for the 5100: "The IBM 5100 Portable Computer" by Harry Katzan, Jr. I found something interesting on page 71 of this book:

Quote:
Nothing that is done from the keyboard can physically damage the 5100 Portable Computer. The worst thing that can happen from "indiscriminate button pushing" is that the user may alter a program or data in main storage.

Now, main storage went away when the power was turned off, so it appears that "button pushing" could only affect main storage, not any hardware or program libraries (which, I believe, resided on mag tapes), or the storage containing the operating system and BASIC and APL languages.

Interesting concept in 1977.


#25

The 5100 stored the OS and language in ROM, as did all HP desktop calculators from HP's Calculator Products Division in Loveland, Colorado starting with the HP 9810A, which was introduced in 1971. (The HP 9100 also used a ROM for code, but the ROM was a 16-layer pc board.) The reason for this "innovation" in code storage was cost. Masked ROM was much, much cheaper than RAM in the 1970s. Even today, DRAM is 4x more expensive per bit than Flash EPROM. The downside back in "the olden days" is that the released code had better be bug free, because you couldn't download new ROM contents. First, the Masked ROM wasn't changeable. Bits were permanently set at manufacturing time. Second, the whole idea of "download" at the then-current maximum speed of 300 bits/sec (as in 0.3 kbits/sec or 0.0003 Mbits/sec) over an acoustic coupler was laughable. Not only was it slow, but the code required to support the download would have occupied too much ROM.

Edited: 3 May 2010, 8:00 p.m.


#26

Steve, that raises an interesting question. My Apple ][+ had a ROM that, I believe, contained the OS and Integer BASIC and Applesoft BASIC. I think my Mac 128k was built the same way, OS in ROM.

What's the current standard for PC's? I gather that most, if not all, of Windows is on disk and loaded as needed into RAM. Is there any ROM on modern PC's?


#27

There are typically 3 programs in ROM on a PC. The BIOS (Basic Input Output System) consisting of POST (Power On Self Test) that finishes by reading the first sector of the drive selected in Setup into a fixed location in memory and transferring execution into that routine, as well as routines for accessing the keyboard, HDD, floppy, serial port, clock &c. Secondly there's the Video BIOS for doing basic character and low resolution graphics to the terminal. Finally there is Setup, which is used to configure the hardware. There may, on some systems, be a bit more, but the OS is always (on modern PCs, of course someone will post the exception) loaded either from storage or through a network connection.


#28

Thanks Mark. That's good to know.

Don

#29

First: more and more manufacturers tend to put a trimmed-down LINUX into the BIOS, so the PC can be used as an "instant-on" multimedia player.

Second: the ROM usually contains a flashing utility nowadays; some "heavy irons" even come with built-in diagnosis tools (that's software way beyond POST and boostrap)

Third: as pointed out, software in ROM better had to be bug free - which rarely happens. While the BIOS resides in an updatable FLASH chip, the CPU itself carries a lot of code in ROM as well - which cannot be altered. So they opted for a clever solution: the CPU itself has a boot code which looks for microcode updates, these are put into the BIOS or OS.

#30

Both my Apple ][+ and Mac 512K required a boot diskette (DOS 3.3 or System x.y) and that was the 'OS'. OS in both cases being the code that allowed a user to interface with the computer to create and manage content. I'd wager that 90+% of the code in the 'OS' called ROM routines.


#31

Ah, but when I got my Apple ][+ it was sans disk drive. I saved my programs to cassette. It was months later that I could afford the 5 1/4 inch floppy disk drives. So the original ][+ didn't need disk drives to operate.


#32

That sounds brutal. I had dual floppies. I just booted up a virtual Apple ][+ and after pressing RESET I was dropped into FP basic. I completely forgot that was an option.


#33

...not to mention Integer Basic! Oh, those where the days... :)

Greetings,
Massimo

#34

Saving and load programs to/from cassette tapes was brutal in retrospect, but at the time I was thrilled to have a computer I could write programs on at all, at home! I loved that Apple. And it would boot in, I don't know, maybe 5 seconds from power on to prompt. Compare that with my current Windows XP which lately I just turn it on and go away for awhile while it does all of its startup things, and I come back in 10 minutes when I can get some real work done without waiting. Now THAT's brutal!


#35

Every new Windows version that Microsoft introduces, they claim it boots faster than previous versions. Mostly, that's a lie. But in the case of Windows 7, it really does boot a lot faster than XP, at least on my HP tablet PC.

#36

3D0G


#37

Howard, that rings a bell, but I can't quite remember which one.

How about Call -141?

Don


#38

Wasn't it ]CALL-151 ? ;)

Greetings,
Massimo


#39

You're right. Call -151 put you in the "monitor", and 3D0G took you back to BASIC.

I really miss the simplicity of the Apple ][. You knew what every file was for. My biggest disappointment when I got a PC was all the thousands of files (now millions, probably) that comprise the "operating system" that you have no idea what they do, and you don't know which ones you really need anymore.

Edited: 5 May 2010, 7:56 a.m.


#40

Quote:
My biggest disappointment when I got a PC was all the thousands of files (now millions, probably) that comprise the "operating system" that you have no idea what they do, and you don't know which ones you really need anymore.

Well, Don, a slight exaggeration. My Windows 7 shows about 46,000 files in the Windows directory (I still haven't gotten used to 'folder'). This includes a lot of unused stuff and files added by the programs I have installed. The original PC-DOS had only a few required files.

Anyway, your point is well taken about the complexity and opaqueness to even the technophiles. At this point I stop, before lapsing into yet another exposition on How Much Technology Do We Really Need?


#41

Yeah, my Windows directory contains just over 36,000 files. My PC is about 7 years old, running XP. It would be interesting to see a graph of the number of files in the Windows directory by age of computer. Or maybe size of registry vs. age of computer.

#42

Quote:
The original PC-DOS had only a few required files.
My first major use of DOS was 3.3, and it fit on a single 5.25" low-density (360K?) floppy disc, and booted faster than modern computers with huge OSes on hard disc.
#43

Ok,

Thought it was Ctrl-C to exit Monitor to Basic ?

Ah, those glorious days...I still treasure my Apple // user and reference manuals :-)

Etienne

#44

Quote:
Steve, that raises an interesting question. My Apple ][+ had a ROM that, I believe, contained the OS and Integer BASIC and Applesoft BASIC. I think my Mac 128k was built the same way, OS in ROM.

What's the current standard for PC's? I gather that most, if not all, of Windows is on disk and loaded as needed into RAM. Is there any ROM on modern PC's?


It's an under-appreciated fact that the ROMs have a lot to do with why the IBM PC was cloned and the Mac was not. As a result, IBM quickly lost all control of the machine that they created and Apple did (and does) keep an tight grip of their hardware.

After the PC came out, several companies reverse-engineered the ROMs in a clean-room environment. This is perfectly legal. And since IBM allowed Microsoft to sell the OS to other manufacturers, it quickly became possible to create an IBM clone.

In contrast, the Mac ROMs were much larger (4MB around 1990 as I recall), so a good chunk of the OS ran from ROM. It wasn't practical to reverse engineer that much code so no one did, at least not successfully.

Dave

#45

Quote:
My Apple ][+ had a ROM that, I believe, contained the OS and Integer BASIC and Applesoft BASIC.

The ][+ came with Applesoft BASIC in ROM. But you could load a copy of Integer BASIC into RAM and have both resident at the same time. (You could do that with the original Apple ][ as well, but there it was Applesoft in RAM.) The new ROMS were
missing some features that the old Integer BASIC ROMS provided. But I know I used the mini-assembler on my Apple //e, so there was some way to get the feature back. I don't recall if it was included in the Integer BASIC disk image or not.

Regards,
Howard

#46

Quote:
Nothing that is done from the keyboard can physically damage the 5100 Portable Computer. The worst thing that can happen from "indiscriminate button pushing" is that the user may alter a program or data in main storage.

I suppose technically it's not the keyboard, but I do know of a case where a 5100 was physically damaged by using a switch on the outside of the box.

I belonged to an Explorer Post which did the scorekeeping for the local Klondike Derby. That's where groups of Boy Scouts pull sledges through the snow and do Scout-types of things. Being sponsored by IBM, we had a couple of 5100s. We also had a stone-and-log cabin with fireplaces blazing at both ends, instead of tents like everyone else. We endured quite a bit of ribbing for being softies.

One morning, to demonstate our operation to the bigwigs, we fired up one of the 5100s before the cabin had warmed up. Sizzle! Pop! Sparks flying!

After destroying $14000 worth of computer gear, we didn't hear any more complaints about our being coddled in our cabin.


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