MS-101 and MS-124 Buffered Mode ROM Upgrade



Windows 95 interrupt latency has increased to the point that high speed serial communication is not generally reliable with com ports using 8250 or 16450 type UARTS. A 16550 type (buffered) serial port will likely be needed, regardless of the external serial peripheral, if baud rates of 9600 or over are desired.

We have added new operating modes to our MS-101 and MS-124 serial MIDI interfaces that are compatible with a high speed buffered com port (16550 UART). All prior operating modes are still supported. Many MS-101s and all MS-124s can be upgraded to add these operating modes. These models use microprocessors with on board ROM (Read Only Memory) that determine their functions.

The upgrade involves changing the processors (which we'll refer to as ROMs for simplicity) which are in sockets. Many units will require circuit board modifications in addition to replacing the ROMs. Problems with Windows 3 enhanced mode will also be eliminated, and full backwards compatibility will be maintained will all software.

Upgrading MS-124s will limit using an external power supply. We have no confirmed cases of anyone needing external power for MS-124 "addressed" mode operation (A/B switch to A - four independent MIDI Outs). DOS operation in "banked" mode(A/B switch to B) may be used with external power. The switch settings will be ignored when using the new "buffered mode", since this mode can only be initiated by a driver. This new mode is "addressed" by default and needs no power supply.

Recently manufactured MS-101s and MS-124s already have the ROM Upgrade installed. You can determine this by checking the first four numeric digits of the serial number. MS-101s whose serial numbers begin with 5307 or higher and MS-124s whose serial numbers begin with 5348 or higher contain the upgrade.


To determine if this ROM upgrade applies to your interface, you will need to determine several things about your system and interface.

1. Verify that your Com Port uses a 16550 type UART

The upgrade is of absolutely no value if the com port to which you connect the interface does not use a 16550 type UART. You can use MSD.EXE that comes with Windows and look at the UART type in the com window. Caution: MSD follows the Windows aberration of numbering the com ports in the order found, so the com port number may not match the industry standard port address. Also, if your BIOS fails to "register" the port base address, MSD may ignore the port! High speed internal modems also use 16550 UARTS, be sure you've identified the external com port, not the modem.

A better alternate is to install the MS-101B/124B Buffered Mode Driver, KEYMSPC3.DRV (KEYMSPC3.ZIP Library) in Windows. The Control Panel/Drivers/Setup Test will give an error message if the com port to which the interface is connected is not 16550 compatible. If the com port passes, the driver will test for the ROM upgrade, notifying of any problems encountered. This is the most reliable test, as you are checking the com port that you will be using.

If your com port uses an 8250 or 16450 UART, you may still have an option. Most desktop or tower systems can be upgraded for relatively low cost. A few laptop or notebook systems can be upgraded, but the cost tends to be prohibitive. Fortunately, most laptop/notebooks of recent vintage have high speed com ports.

2. Verify that your MIDIator model can be upgraded

All MS-103s and early MS-101s used hard-wired circuitry instead of microprocessors, making a ROM Upgrade impossible. These MS-101s may identified by two characteristics. First, "MIDIATOR tm" is printed on the sides of the unit. Second, the MIDI IN and MIDI OUT connectors are screw mounted and very close together (approximately 1.2 inches or 3 cm center-to-center). If an MS-101 meets either characteristic, then it CAN NOT be upgraded. Don't toss it out, however, as it is still useable as a MIDI OUT device for any current Windows version.

Later MS-101s have no printing on the side. The MIDI IN and MIDI OUT connectors have no connector mounting screws, and are much further apart (approximately 3.5 inches or 8.9 cm center-to-center). Finally, "MS-101" is printed on the top of the cover.


Upgrade Kits

As some owners will not want to return units for a factory installed upgrade because of time constraints or high shipping costs, we will make ROM Upgrade Kits available. These contain all needed parts and instructions. Kit installation should only be attempted by a competent electronics technician. There will be a repair charge on any interfaces returned with problems caused by faulty upgrade kit installation.

Factory Upgrade

Simply return your interface to us. We'll check it out completely, install the ROM upgrade, and test everything thoroughly before returning the unit. If we receive a damaged or non-working unit, we'll notify you of any needed repair charges before proceeding.

Windows Driver

All ROM Upgrades include an MS-101B/124B buffered mode Windows MME driver for Win 3.1, 3.11 and 95. The driver is supplied on a 3.5" floppy disk.

ROM Upgrade Prices

The ROM Upgrade will be of absolutely no value unless used with a high speed com port (16550 compatible UART). Make sure of this before returning units for upgrading or ordering upgrade kits! Also, be sure to specify the model correctly, as the kits are different.


MIDIator Systems
(858) 481-1663