
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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