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IBM 5150 Resto - Would you upgrade the ROM from ver 2 to 3?

S

Springbok

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Orlando, FL
OK,

So I have almost completed my restoration. It's a model A with the very hard to find version 1 case, but has the version 2 PSU (the one with the sunken scews) and version 2 of the BIOS.

It came with no floppies, since it was expected that you would boot from cassette. However that really isn't practical, so I installed 2 full height floppy drive, and the controller.

I have this really cool HD that fits in an ISA slot. Problem is that unless I upgrade the BIOS to version 3, the 5150 Model A can't use the Hard drive. Would you upgrade it, or leave it alone?
 
Do you have an AT? I left mine stock so I can play floppy booters and I have NECV20 and AT/286 machines anyway.
 
If you have the black PSU, I do not recommend plugging the hard card into the system. You'll probably blow the power supply. If you have the 63.5 watt silver PSU, you'll want to check carefully what the power draw of the hard card will be so you don't blow it. As the rev 1 and 2 bioses are tough to come by, I personally would leave it stock, install a network card and run novell lite or lantastic if I needed more storage. I have a REV A 5150 all stock with low density drives and I am not touching it.
 
So you do have a genuine diskless 5150? I've had more than one that was configured that way when I got it, but never was certain they were originally set up like that.
 
I can recall that this was the basic option for the model A. Some even came with only 16K of RAM installed.

You can always save the original ROM if you got a hankering to downgrade. I see no problem with changing a single BIOS chip. You could also handle the issue by always booting from floppy and then running a little program to initialize the hard drive, then do a "warm" reboot. I did that back in the day with my model A. It worked fine.
 
I'd probably leave the BIOS ROMs where they are.

The third version of the BIOS allows for BIOS extensions on expansion cards, which is how the hard drive controller installs its BIOS. I think that EGA and VGA cards also need to install a BIOS to be usable. So the machine is limited to a floppy drives and the first generation of video cards.

If you really want mass storage you can do something like use a parallel port Zip drive with the Palmzip drivers. Or you can get a parallel port to SCSI adapter and use an external SCSI drive. Both would require you to boot from floppy disk first, but it keeps the machine original. PCjr owners have been working that way forever, since the PCjr BIOS doesn't know about hard drives and hard drive adapters with a BIOS were very rare.

The other glitch with the early versions of the BIOS is that RAM is limited to 544KB. You can put more in, but the BIOS won't see it. This probably can be fixed by patching memory locations after booting.
 
Let's be clear here--it's only one ROM--the others are for ROM BASIC and they're the same.

A 68764/68765 EPROM will work just fine and is 24-pin socket compatible.
 
Springbok said:
I have this really cool HD that fits in an ISA slot. Problem is that unless I upgrade the BIOS to version 3, the 5150 Model A can't use the Hard drive. Would you upgrade it, or leave it alone?
Click to expand...
To use a HDD, you would also need to upgrade the PSU, as it's too weak for powering a HDD. Because of that I'd say: leave it as is.
 
Timo W. said:
To use a HDD, you would also need to upgrade the PSU, as it's too weak for powering a HDD. Because of that I'd say: leave it as is.
Click to expand...
It's most like not that kind of drive, FH or even HH MFM. More than likely it's a low power IDE on an ISA card (what's known as a hardcard) and probably uses very little current.
 
I'm aware of that. Still, the PSU only offers 63 watts (likely less due to its age) and especially the 12v line is already quite stressed with two floppy drives installed. The PSU will most likely shut down when accessing a floppy disk when having a HDD installed.
 
My later model 5150 with 63 watt PSU was originally bought with 1 FH Floppy drive, Some time later the original owner had a 2nd FH floppy drive fitted and a 20 Mb Plus Card fitted, The 63 Watt PSU had no problems coping with the extra load, I bought the machine from the original owner but removed the Plus Card a short time later because the drive was too noisy for me. I agree with Chuck the XT-IDE CF card's are an excellent choice.
 
Timo W. said:
I'm aware of that. Still, the PSU only offers 63 watts (likely less due to its age) and especially the 12v line is already quite stressed with two floppy drives installed. The PSU will most likely shut down when accessing a floppy disk when having a HDD installed.
Click to expand...
Although, if a hard drive is going to cause a PSU overload problem, then I expect that to occur at power-on time.
Refer to my diagram at [here].
 
hello
Chuck -question, what small program do you use for the initializing of the HD ?
/cimonvg

Chuck(G) said:
I can recall that this was the basic option for the model A. Some even came with only 16K of RAM installed.

You can always save the original ROM if you got a hankering to downgrade. I see no problem with changing a single BIOS chip. You could also handle the issue by always booting from floppy and then running a little program to initialize the hard drive, then do a "warm" reboot. I did that back in the day with my model A. It worked fine.
Click to expand...
 
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