PS2 FAQ- IO Controllers/Interfaces

Archive-name: PS2-FAQ - IO Controllers/Interfaces
Last-modified: 1996/02/20
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Version: 4.0
Author: Chris Feeny <Alkemyst>

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S) 3.0 IO controllers/interfaces

Q) 3.1 How do IDE/MFM/RLL/ESDI/SCSI interfaces work?

Q) 3.2 How can I tell if I have MFM/RLL/ESDI/IDE/SCSI?

Q) 3.3 Why won't my two hard drives work together?

Q) 3.4 How do I install a second controller?

Q) 3.5 Which is better, SCSI or IDE or ESDI?

Q) 3.6 Can MFM/RLL/ESDI/IDE and SCSI coexist?

The PC is limited to two drive controllers total. SCSI, however, is a "host adapter" and not a drive controller. To the rest of your system, it appears more like an ethernet card than a drive controller. For this reason, SCSI will always be able to coexist with any type dive controller. The main drawback here is that on most systems, you must boot off a disk on the primary drive controller, if you have one. That means if you have SCSI and IDE in your system, for example, you can not directly boot from the SCSI drive. There are various ways to get around this limitation, including the use of a boot manager.

Q) 3.7 What's the difference between SCSI and SCSI-2? Are they compatible?

The main difference between SCSI and SCSI-2 are some new minor features that the average person will never notice. Both run at a maximum 5MB/s. (note: Fast and Wide SCSI-2 will potentially run at faster rates). All versions of SCSI will work together. On power up, the SCSI host adapter and each device (separately) determine the best command set the speed that each is capable of.

For more information on this, refer to the comp.periphs.scsi FAQ.

Q) 3.8 What is a 16550UART and do I need one? Does my PS/2 have it?

The 16550 is a UART with two 16 byte FIFOs. A UART is the part of a serial port that takes byte-wide (characters) data and converts it to bit-wide (serial) data, and visa versa. The FIFO is a buffer which can hold characters until the CPU is ready to remove it or until the serial line is ready to transmit it. The 'normal' UART in the PC (the 8250 or 16450) only has 1-byte FIFOs. The additional 15 bytes can be useful when the CPU is busy doing other things - if the CPU isn't able to remove data fast enough, it will be lost. The OS or program has to explicitly support 16550 to make full use of its advantages.

A very important thing to note is that under DOS, the CPU doesn't have anything else to do, so the 16550 is wasted. Only under multitasking operating systems does it really become useful. The 16550 will *not* make your file transfers any faster, it will only prevent data from being lost and relieve your CPU of some overhead. If you notice system performance dropping like a rock when file transfers are occurring, a 16550 may be helpful. If you see re-transmissions (bad packets) or "FIFO overrun's" during file transfers under a multitasking OS, try the same thing under DOS - if the errors go away, then chances are a 16550 will be useful. If they remain, then your problem is likely to be elsewhere.

PS/2s without the more modern 16550A UART are usually limited to lower data rates (not because of the 16550 UART but because the other UARTs are slow). Usually 14.4k max with no compression. The PS/2 models and type of UART are listed below.

From: Aron Eisenpress <AFECU@CUNYVM.CUNY.EDU>:
The following information is taken directly from the PS/2 Hardware Interface Technical References.

Four types of serial port controllers have been used on the system< boards of PS/2's.

To programs, the Type 1 controller appears to be identical to the serial port< on the IBM Personal Computer AT IBM Personal Computer Serial/Parallel Adapter.

The Type 2 controller incorporates all functions of the Type 1 and also provides support of the first-in-first-out (FIFO) mode.

The Type 3 controller incorporates all functions of the Type 2 controller and provides the Direct Memory Access (DMA) mode.

The Type 4 controller incorporates all the functions of the Type 3 controller and provides additional I/O addresses.

For type 1 and type 2 controllers data speed should not exceed 19.2kbaud. Type 3 and type 4 controllers support up to 345.6 kbaud.

Below is a list of the type of serial controller used in each model in the Micro Channel PS/2 line:

Model Type of Serial Port Max Speed
----- ------------------- -----------
8550 1,2 19.2 Kbaud
8551 (N51) 2 19.2 Kbaud
8554 (CL57) 2 19.2 Kbaud
8555 2 19.2 Kbaud
8556 4 345.6 Kbaud
8557 4 345.6 Kbaud
8560 1,2 19.2 Kbaud
8565 2 19.2 Kbaud
8570 2 19.2 Kbaud
8573 (P70) 2 19.2 Kbaud
8580 1,2 19.2 Kbaud
8590 3 345.6 Kbaud
8595 3 345.6 Kbaud

IBM uses a proprietary chip instead of the 16550 UART in PS/2's. The serial
port controller in all of the above PS/2 models (except the PS/2 models 55
and 65) is compatible with the National Semiconductor NS16450 serial port.
The serial port controller in the PS/2 models 55 and 65 is generally
compatible with the NS16550A serial-communications controller.

Also note, the lesser UARTs are sometimes ID'd as a 16550AF these are the ones
incapable of greater than 19.2k transfers.
PS/2's with Type 2, Type 3, or Type 4 serial port controllers support the
first-in-first-out (FIFO) mode. The exception is the PS/2 model 50 with a
Type 2 serial port controller. According to the PS/2 Hardware Interface
Technical Reference - System Specific Information, model 60's and 80's with
Type 2 serial port controllers do support FIFO mode.

[incomplete please help me obtain the UART data on the other PS/2s. A good
program is Snooper v3.30 by Vias and Associates for $39 available as shareware
on most BBSs and internet ftp sites, please register if you decide to keep it]

Q) 3.9 Should I buy an internal or external modem?

In general, it is better to go with an external modem for two reasons. One
MCA slots are valuable commodities in most systems (ie Model 50s with only 3
slots) and Two an MCA card modem will be alot more money when a standard
external modem will work fine. Also an external modem provides visual clues
to tell you what is going on with the data.

Sometimes internal is the only way to go though. The Windsurfer Adapter
with its 14.4k data modem, 9600 FAX and telephone answering/voice mail is
only available internally, however, this is not such a waste of a MCA slot
as you are getting several products on one card.

Q) 3.10 What kinds of sound cards are available?

There are a few believe it or not and cost not that much more than standard
soundcards. The original was the SoundBlaster MCV which is an 8bit card and
probably should be avoided due to the problems it has with compatabiliy.
The SoundBlaster Pro MCV is a 8bit card which supposedly works better, yet
both soundblasters are no longer made. The next option is the Audiovation/A
($249) which is a 16bit card capable of 44.1KHz sampling rates is
SoundBlaster compatable and is currently being revised for better support.
Another option is the M-Audio Capture/A which is said to be more of a sound
editor than one for games. Another option is the WindSurfer Card. This is
probably overkill as solely a soundcard for its $400 low price, but it does
offer a 14.4k modem, 9600 FAX and telephone answering/voice mail on one card.
This card is probably not as compatable as the Audiovation is, but maybe
worth a test to see if it does what you would like. The Chipchat is
currently available and is wavetable capable ( or
(313)359-0900). Reply Technologies has a card out using the chipset from
Creative Labs, the Vibra 16, which is SoundBlaster 16 compatable and it
is also available linked up to a Future Domain SCSI-2 controller. One
more option comes from Piper Research at 715-386-7899, this is a
SoundBlaster compatable card.

Here is the specs to the Piper Card:
(From: (Eric J. Fluhr) and (Cory Kim))

Piper Research, Inc.
4716 Nord Drive
Bloomington, MN 55437
Office: (612) 888-5690
Fax: (612) 730-5860
To order: (715) 386-7899

16 bit stereo sound card. Records, compresses and plays back voice,
sound and music with computer controlled mixer settings and Yamaha OPL-3
based FM synthesis. In addition, connections are provided for CD-audio,
line-in, joystick MIDI and speakers. Other key features include:

o Micro Channel Architecture compatible o 4 Watt Stereo Amplifier
o Half-Size Adapter o Compatible with all Major
o Auto-configures like all MC cards Software Programs
o Multimedia PC Compatible o Stereo Mixer & Amplifier
o Integrated 16-bit A/D and D/A Converters o Patented ESPCM Compression
o Programmable Digital Volume Control o Windows compatible and
o Programmable Sample Rates to 44.1 kHz OLE Compliant
o Several bundled Applets
and drivers

IBM is supposedly in the process of creating a new line of soundcards, both
more compatable and better performing. However, expect to pay a premium at
first as MCA cards are being bought up faster and faster lately.

The SoundBlaster and Piper Cards are industry standards and thus offer the
most compatability in most games Piper uses the Soundblaster Pro Chip from
ESS. Most these cards may cause problems in the Windows environment as they
were developed before Windows was around, however for DOS games the
SoundBlaster Pro is THE card to have. The Audiovation/A and the others only
emulate a SoundBlaster using Mwave technology which is THE thing for WINDOWS.
So depending on what you do most choose a card, also two cards can be used if
the reference disk is patched.

There has been much discussion regarding PS/2 Micro Channel - MCA - sound
cards. Here is a quick comparison. This comparison addresses both hardware
and driver capabilities. It is important to consider both, since if there is
no driver to support a hardware capability then the capability is not useable.
A perfect example is OS/2 drivers. Although each sound card in this
comparison has "16 bit"record/playback hardware, some cards use the
"SoundBlaster Pro MCV" driver shipped with OS/2 Warp. This driver only
supports "8 bit", not allowing "16 bit" files to be recorded or played.

CARD -> ChipChat-16 ChipChat-32 Piper-16 Reply

16 bit rec/play YES YES YES YES
WaveTable upgrade YES NO upgrade
Stereo Mixer 6 Channel 6 Channel 5 Channel 5 Channel
SoundBlaster YES YES YES YES
CD audio connectors YES,4 YES,4 YES,1 YES,1
IBM Front Panel conn. YES YES ? NO

16 bit rec/play
WaveTable support
DOS upgrade YES NO upgrade
WIN 3.1 upgrade YES NO upgrade
WIN 95 upgrade YES NO NO
WIN NT upgrade YES NO ?
OS/2 upgrade YES NO NO
AIX upgrade YES NO NO
General Midi upgrade YES NO YES
Roland MPU-401

DOS GAMES - Out of the box play no problem
DOOM YES YES Problems Problems
Game with WaveTable YES YES NO sometimes

AGENCY APPROVALS - YES means can sell and ship to those countries
World Wide Approvals YES YES NO NO
CSA (Canadian) YES YES ? ?

Also see Appendix F for a full listing of PS/2 Sound Cards.

Q) 3.11 Can I run both a SoundBlaster and the Audiovation/A?

[ (Alain Jacques)]
Yes, it works ... after patching the ADF file. What's conflicting is the
addresses of the game port, defined in both ADF's as fixed resources and
therefore the conflict cannot be managed by the POS itself. If you choose to
keep the game port on the SBPro, just as I did, your Audiovation ADF file
@8FD6.ADF should look like the end of this message.

If you have difficulties, don't hesitate to email to me. BTW, there are new
Audiovation Windows drivers on IBM PC Co BBS (i.e. version 2.1 = av211.dsk,
av212.dsk, av213.dsk, av21util.dsk).

See Appendix C for Program listing.

Q) 3.12 Can I fake a keyboard so my computer will boot without it?

Well unlike the standard IBMs and clones, PS/2s perform a keyboard test at
boot. Some have the option of cancelling the keyboard test through a setting
in the reference disk. If you do not have this option you must leave the
keyboard attached (or if you have the engineering experience doctor up a small
board that sends the proper reponses to the test back and can plug into the
keyboard port :) ).

email:Chris Feeny

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