CD-ROM ON MSX !? (Part 1)

Written by Henrik Gilvad.


Many years ago Philips did a SASI interface for the MSX so 
they could connect a CDROM drive to it. The SASI is a kind of 
version 0.5 of SCSI. SCSI can usually run SASI devices.
Philips was probably 10 years too early with this interface 
because back then it costed a lot to make a CD and the drives 
was also too expensive for normal people to buy.

Today CD-ROM is 1/2 of the total european and american 
software market and it's still growing. CDROM drives are also 
getting down into a price where we can buy them for MSX.

What it takes to use CDROM on MSX is:
1) SCSI interface. (170-300kbytes/sec)
2) SCSI CDROM drive. Preferable a double spin multisession.
3) Software which can understand the CD format.


A few weeks before Tilburg 1994 I borrowed a SCSI CDROM drive 
from a friend and connected it to my SCSI interface. The 
nextcomming weekend was used to explore the CDROM directory 
and file structure. On Saturday early morning I could locate 
files from a HEX dump of the 'directory' and on Sunday I had 
made a simple CDROM program in basic/machinecode.

Now I thought the worst was over but WHAT should I use a 
CDROM drive on MSX for ?

The answer was comming when I looked on my 245Mbytes 
harddisk. It is filled up with GIF, FLI, BMP, MOD and PCM 
files. Exactly these filetypes are what is filled on PC and 
aMIGA CDROM's and sold with 100-600 Mbytes on them for about 
100-250 DKr. (30-72 Hfl.)

So far there is no MSX software on CD, except from the 1 CD 
that Philips made for their MSX SASI interface. But it is not 
programs which are taking all the harddiskspace, its the huge 
amounts of graphics and music.


The price of a CDROM drive is often no higher than the price 
of a resonable harddisk. When you have the CDROM drive you 
can get 600 Mbytes for almost no money. Today I have 18 CD's 
with at many gigabytes of USABLE data for the MSX.


From March-July 1994 the following CD-ROM features have seen 
the light on MSX. I will descripe them in other texts on the 
Quasar disk.

* Access to all sorts of files. (GIF, BMP, MOD ...)
* Photo CD pictures.
* Music CD replayer and database.
* Realtime PCM replayer of PCM files.
* aMIGA CD32 background music replayer.

The future might bring us:
* 16 bit stereo PCM ripper for Music CD's.


I will not go into details about how data are stored on the 
CD's. This can be read in any PC magazine and is almost 
without any value of information. A few informations are 
comming here:

The 'standard' CDROM should follow the 'High-Sierra' or 
'ISO9660'. HighSierra was named after the hotel where one of 
the first serious CDROM conferences was held. Later the 
standard they came up with was established in the ISO-9660.
Since there are so many different computers with so many 
different fileformats then the ISO-9660 have been split up 
into 2 levels:
LEVEL1: Filenames in Uppercase and Length of max 8 + 3 chars.
LEVEL2: Filenames with any letters and longer names.

Level1 is the one used for DOS machines, thus MSX.
Level2 is used in aMIGA, early MAC, CD32 etc.

The Level2 is not so difficult to read but the filenames does 
not fit our DOS very well.

Data is not stored as 8 bits but as 14 bits. But take it 
easy, there are only 8 data bits in each 14 bit group. This 
is done to minimize some kind of errors.
The 'tracks' are only 0.6um wide. The rotation speed is 
regulated so that there are 75 'frames' (sectors) each second 
on a single speed drive. The CD standards have been descriped 
by Philips in the following books:

Red book (Digital Audio, CD-DA = Music cd's)
Yellow book (CD-ROM) Have 2 modes.
Green book (CD-I) Is actually Yellow book mode 2 but with 
some infofields.
Orange book (CD-WO, CD-MO) Write Once, Magnetic Optical.

Unfortunately then some computers likes to do their own 
'standards' so they can claim that it was THEM who invented 
everything. Some of these are aMIGA and MAC. Today aMIGA 
finally use ISO9660 level2 but MAC seems to go into their own 
format which they feel is absolutely nessesary for their 
'multimedia' CD's. So don't be sure that data from MAC can be 
read on MSX.


In TILBURG 1994 I was standing at the MSX Handlergemeinschaft 
stand and showing many things. One of these things was a 
PC-BOX with a MSX slotexpander, harddisk, V9990 and CDROM 
drive. Unfortunately people just walked on because they 
thought it was a PC. But we have NO PC's with us. The next 
chance to see CDROM is in Zandvoort, so be there !


Now I will answer some frequently questions that I have got 
from MSX people:

Q: What do I need to use a CDROM on MSX ?
A: A "WD33C93A" scsi interface like the one I did for Gouda 
and MSX Handlergemeinschaft. You can therefore also use a HSH 
interface or some of the clones like the older MK interface. 
You will need a SCSI CDROM drive as well. You can use CDROM 
also on MSX 2 but some of my CDROM programs are for Turbo R 
only. Last but not least you will need some software which 
understands the CDROM format and can controll the SCSI 
interface.

Q: Playing Music CD's in 44.1kHz, Stereo must be very time 
assuming ? How much is the MSX slowed down ?
A: Most CDROM drives have a build in Music CD function and 
its own 16 bit stereo D/A converter. Therefore even a 3.5 MHz 
MSX can play CD's because it only have to start the replaying 
by sending over some SCSI commands.

Q: What fun is it to play PCM files from CDROM ? We only have 
512kbyte ram on the Turbo R and the PC's have at least 4-8 
Mbytes.
A: HA ! My Turbo R PCM file replayer needs only 16kbytes of 
memory, then it can play files of any size and in any speed.
The maximum data are: 8 bit Stereo aprox. 150kHz samplerate.
The stereo need a Philips module for the second channel.

Q:Can I use a IDE/ATBUS CDROM drive ? They are so cheap.
A:NO, only SCSI ! The real cheap ATBUS drives are often only 
single speed (150-170kbytes/sec) and have a very bad Audio CD 
part so the sound will be bad. Do yourself the favoir to buy 
a SCSI drive because there are made for PROF users !

Q: Will there ever be any MSX software on CDROM ?
A: No one can promise a lot of CD roms for MSX without taking 
a great risk to loose renome. Since CDROM is so new there 
will only be a small market, the never ending problem when 
new hardware is develloped. The REAL need for CDROM is in 
MASS-Storage. Today it is usually cheaper to make a CDROM 
than to use 2-3 floppy disks on the PC. When we get better 
PCM and higher graphical resolutions then we also need more 
disk-space. There ARE MSX people who are talking about making 
CD's with MSX programs/games but these are probably FREAKs 
(like me). Usergroups would probably like to have a CD with 
all MAD's PD disks. Or what about a CD with all MSX music 
ever made or CD's filled with MOD, GIF etc. ?
Doing software on CDROM, to be runned from CDROM, will set 
some demands to the software because it must only run in DOS2 
and probably use ASCIIZ dos functions for the files.
I think the best thing is not to expect lots of CD's with MSX 
programs. But I think that CD's with data will be realistic 
to believe in.

HG
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