XROM / XDROM - Extended ROM for Model 4/4D/4P systems

The XROM or XDROM improve performance when using any Model III operating system or ROM BASIC. They also allow you to boot directly from a hard disk (such as LS-DOS 6.3.1) or boot using Network III or 4 hardware. These ROMs replace the "C" ROM or "D" ROM in your Model 4 or 4D. Detailed instructions assist you in removing the cover and installing the ROM in your system. Installation in most cases takes less than 30 minutes. The new Model III-mode features include:

The keyboard produces all 128 ASCII characters, handles key-rollover, and performs "debouncing" correctly at 2 and 4 MHz.
The keyboard repeat rate is adjustable.
The time-of-day clock keeps correct time even when the system is running at 4 MHz. The cursor also blinks at the same rate regardless of the current CPU speed.
A fully programmable 6845 CRT controller can be used in place of the 68045 used by Radio Shack.
All calls into the "C" ROM that are documented by LDOS and Radio Shack produce the same results as in the original part.
Interrupt-driven software performs more reliably than in the original "C" ROM.

The XROM/XDROM comes with documentation on the new Model III-mode features. The XDROM includes built-in tests for memory, video, floppy drive, and printer (available via a factory test option jumper.)

System Requirements:
CPU	Model 4 non-gate-array systems should order "X" ROM. Model 4 or 4D gate-array systems should order "XD" ROM.
Processor	Z80A or a superset processor, including the XLR8er accelerator. *
Floppy Drive	Any Radio Shack-compatible configuration including no drives.
Hard Drive	Any Radio Shack-compatible configuration including no drives.
Operating Systems	The following systems have been tested: LDOS 5, TRSDOS 6, LS-DOS 6, CP/M+, NEWDOS, TRSDOS 1.3/1.4.
Firmware	Model 4 owners must make sure that they have the latest "A" ROM, Radio Shack part number 8048364A. ** Model 4s built after 1983 and Model 4Ds should have the correct part.
Hardware	The XROM/XDROM may be used with a SmartWatch(TM) clock chip. (Model 4 owners must not have disabled wait-state generation for ROM accesses.)
Keyboard	Only US-layout keyboards are supported. Systems with German or French keyboards cannot use XROM, or XDROM.

*

The XLR8er(TM) accelerator is supported provided that it worked with the system prior to the installation of the XROM or XDROM and your system has not been modified to defeat the wait-state generation for ROM accesses.

Model 4's built in 1983 may also require a new "A" ROM to be able to use the "X" ROM. To test your machine, boot your system into ROM BASIC (hold down the BREAK key and press RESET.) Once you are in ROM BASIC, type the following statement:

       PRINT CHR$(PEEK(1490))

and a single character will be displayed. If the character that was displayed is 'O', then you have the old "A" ROM and must replace it to be able to use the "X" ROM. The current "A" ROM is listed here.

Ordering Information

Important: Most HBUILD6 packages include an XROM or XDROM. If ordering one of those packages, you don't need to order XROM or XDROM separately.

ROM Type	What computer and what hard disk drives it is used with	Part Number	Price
XROM for non-gate-array Model 4 systems	Extended ROM for non-gate-array Model 4 systems With hard disk driver for Radio Shack WD1000 or TB1 controllers	4BXR650	$18.00
XROM for non-gate-array Model 4 systems	With hard disk driver for MISOSYS SCSI Host interface and Adaptec or XEBEC disk controller	4BXR655	$18.00
XROM for non-gate-array Model 4 systems	With hard disk driver for non-Radio Shack WD1000 controllers that are port-mapped at 0x78 - 0x7f	4BXR657	$18.00
XDROM for gate-array Model 4 and Model 4D systems	With hard disk driver for Radio Shack WD1000 or TB1 controllers	4DXR670	$28.00
XDROM for gate-array Model 4 and Model 4D systems	With hard disk driver for MISOSYS SCSI Host interface and Adaptec or XEBEC disk controller	4DXR675	$28.00
XDROM for gate-array Model 4 and Model 4D systems	With hard disk driver for non-Radio Shack WD1000 controllers that are port-mapped at 0x78 - 0x7f	4DXR677	$28.00

How to place an order with M. A. D. Software.