A few MT-32 questions

[JeffPaine]

I got an MT-32 last night on eBay (my first one ever), for an old computer I'm building. I wanted to get a second-generation MT-32 (with the headphone jack) but after a month or so of not finding any on eBay I got impatient and bought a first-generation unit. Now, will this have a lot of buffer overflow errors on a 486DX-33, or is that slow enough where it won't be much of a problem? (mainly going to be playing Sierra games on the PC)

Also, I'm planning on getting a SC-55 for later Sierra games and other newer games that were designed for General MIDI (7th Guest, etc) What would the best way to hook that up alongside the MT-32 be? Should I get another interface card, or run it through the MIDI THRU on the MT-32, or something else?

[Tom]

Welcome aboard, Jeff!

You shouldn't experience problems with buffer overflows with a 486 processor sending the data to the MT-32 when  running Sierra games.  I don't recall ever having problems with too fast SysEx sends untill my first Pentium days.  But if you do, disapling the system's cache (in CMOS) or using an utility like 'Turbo' or 'MoSlo' will take care of it. 

Preferably, a seperate interface would be ideal for a second sound device.  Then you don't have to mess around with disabling channels, muting volumes, and so forth with one or the other.  But you CAN run the SC-55 from the MT-32's THRU connection and just turn down the MT-32's volume when playing SC supported games.  Because I mostly use my sound devices for composing, I'm always thinking of the best ways to handle multiple sound devices based on my preferences.  I'm curious how others would handle it, too.

[NewRisingSUn]

Now, will this have a lot of buffer overflow errors on a 486DX-33, or is that slow enough where it won't be much of a problem? (mainly going to be playing Sierra games on the PC)

Sierra games should be fine on systems of any speed if your ISA bus speed is correct --- Cloudschatze and I have found that this is too often not the case. Just try it and see if you get any error messages.
You'll definitely have problems with LucasArts games though.

Should I get another interface card, or run it through the MIDI THRU on the MT-32, or something else?

A seperate inferface card is only necessary if you want to control the MT-32 independently from the SC-55, for example if you use both for composing. If you'll only be using one at a time, connecting them via MIDI THRU and turning down the volume of the other, unused, module is probably the easiest and cheapest approach.

[Great Hierophant]

Sierra games should be fine on systems of any speed if your ISA bus speed is correct --- Cloudschatze and I have found that this is too often not the case. Just try it and see if you get any error messages.
You'll definitely have problems with LucasArts games though.

What are the limits of the ISA bus speed?  In my mind, anything from 4.77MHz for an XT bus and 6MHz to 8.33MHz should be valid for an AT bus. 

[NewRisingSUn]

Within the same system, 8-bit cards (like the MPU-401/AT) should run at 4.77 MHz, 16-bit cards should run at 8.33 MHz. Nothing else. Some mainboards run the 8-bit cards at 8.33 MHz as well, which does cause problems with Sierra games (the "Excl. Checksum Error", not the "Excl. Buffer Overflow").

[Great Hierophant]

Within the same system, 8-bit cards (like the MPU-401/AT) should run at 4.77 MHz, 16-bit cards should run at 8.33 MHz. Nothing else. Some mainboards run the 8-bit cards at 8.33 MHz as well, which does cause problems with Sierra games (the "Excl. Checksum Error", not the "Excl. Buffer Overflow").

I was not aware that you could change the ISA bus speed to run certain cards and slots at a slow speed and a other cards and slots at a high speed.  It sounds complicated to implement in hardware, as the system would have to autodetect an 8 or a 16 bit card and set the speed for that slow accordingly. 

Also, the MPU-401AT's manual specifically excludes the IBM PC, saying it requires an AT-class system or better to work.  Maybe the board is designed to work at a 8.33MHz bus speed and won't work with a slower bus speed. 

It is also important to note that most IBM PC ATs, which introduced the 16-bit bus, ran it at 6MHz just like the processor.