Radio Shack ROMs and PALs

These ROMs and PALs were obtained from Radio Shack when they reduced their Model 4, 4D and 4P parts inventories. We carry them for people who desire to make their own repairs or upgrades. Unless otherwise stated, documentation is not provided with these replacement parts.
Attention: Radio Shack has disposed of their entire spares inventory of components for the TRS-80 systems. We will continue to carry these remaining parts until our supply is exhausted.

Model 4/4D "A" ROM - 8048364A - Checksum 8F46

The latest "A" ROM, used in all Model 4 and 4D systems. This part replaces the obsolete 8048364, which was used in early Model 4 production runs. (All Model 4D systems should have come with the newer part.)
A 8048364A must be present in a Model 4/4D for HBUILD6 and the XROM/XDROM products to work correctly. (Note: This newer "A" ROM cannot be used with an old "C" ROM. The "A" and "C" or "D" ROMs are a matched set. The XROM replaces the "C" ROM and the XDROM replaces the "D" ROM.)
To order, Specify 4GR64A0 $20.00

Universal Character Generator - used in all Model 4/4D/4P systems

If your Model 4 was built before 1984, it may contain an obsolete character generator. About that time, Radio Shack switched to a "universal" character generator which was used in all subsequent U.S. and international versions of the Model 4, 4P, 4D and 2000. To check to see if you have the older part, go into Model 4 Disk BASIC and type:

     ?CHR$(0);CHR$(26) <ENTER>
If a vertical line is displayed, then you have the newer part. If you see the letter 'a' or some other character, you should consider upgrading your machine. Instructions for installation of this genuine Radio Shack part are included. Documentation on the universal character set begins on page A-58 of the TRSDOS 6.2 Disk System Owners Manual.
To order, Specify 4GRCG00 $15.00

Model 4 "B" ROM - 8040332 - Checksum 407C

For non-gate-array (three-ROM) Model 4 and Model III systems.
To order, Specify 4BR3200 $10.00

Model 4 U4 PAL - Video clock generator - 8075268

For non-gate-array Model 4 systems.
To order, Specify 4PU4000 $8.00

Model 4 U59 PAL - ROM/Video/Keyboard address decoder - 8075368

For non-gate-array Model 4 systems.
To order, Specify 4PU5900 $8.00

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