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IBM PCJX Rom

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IBM PCJX Rom

by scamp3 » Thu Jun 10, 2010 5:50 pm

Hi Everybody,

Just wondering if anybody has an IBM PCJX ROM upgrade they would be willing to part with or sell.

The ROM upgrades the floppy drives from 360kb to 720kb
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Re: IBM PCJX Rom

by tezza » Fri Jun 11, 2010 10:25 am

You mean the 3.5 disk drives in that things are only 360k? Are you sure? I thought all JX's came out with 720k drives?

I mulled over bidding for this unit myself but I decided it would be beyond my capabilities to fix the character fault. What do you think of the machine now you have it? They seem interesting beasts and are quite rare worldwide.
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Re: IBM PCJX Rom

by tezza » Fri Jun 11, 2010 10:27 am

Ok, I just answered my own question. You must indeed have the old ROM. From Wikipedia...

"The system operated PC-DOS 2.11 and Advanced BASIC. Like the IBM PC, if the system was left to boot without inserting a diskette into one of the drives the BASIC interpreter would be loaded, which was compatible with IBM PCjr BASIC, including Cartridge BASIC. PC-DOS 2.11 could only use half of the tracks of a 3.5" drive, however, since it didn't really understand what a 3.5" drive even was. The PCjx's BIOS pretended that it was a 5.25" drive.

The PCjx later had a BIOS upgrade chip, sold together with DOS 3.21, which permitted the full 720kB capacity of the diskette drives to be used. Some popular options for the PCjx were a 10MB external hard disk (as a stackable unit the same size as the JX itself) and a joystick. IBM never released any kind of 3270 emulation adapter for the PCjx in order to steer enterprise customers to more expensive PCs and PC XTs."
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Re: IBM PCJX Rom

by scamp3 » Fri Jun 11, 2010 9:22 pm

I absoulely love this machine apart from the character problem everything else is great, I haven't tried the infared in the keyboard yet but it's a very clean well kept machine. I think I might leave the character problem alone.

I took it to show my tutor where I am doing my course and he worked for IBM for years. He used to own a JX and a collegue of his at IBM modified the ROM in his machine so it could read 1.44mb disks.
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Re: IBM PCJX Rom

by tezza » Fri Jun 11, 2010 10:11 pm

A kind of souped-up PC Junior. I wonder how well they actually sold in NZ, Aus and Japan? I never seen one in the flesh myself.
Tez (Terry Stewart) (Administrator)
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