Fantastic, thank you very much for doing this!tcdev wrote:Here's the completed schematic traced from my 1MB/8Mb DRAM Daughterboard...
http://members.iinet.net.au/~msmcdoug/c ... ematic.pdf
Super Magic Drive research thread
Moderator: BigEvilCorporation
-
Charles MacDonald
- Very interested
- Posts: 292
- Joined: Sat Apr 21, 2007 1:14 am
Re: 1MB/8Mb DRAM Daughterboard schematic
The good news is that I've fixed my DRAM problem. When I repaired the battery damage on my board, I neglected to notice that a few of the pins in the DRAM daughterboard connector were corroding.
I replaced the connector on my SMD PCB and now it shows "RAM 8M"
The bad news is that I still cannot get the disk read/write to work. I do believe it is writing, but it simply refuses to read anything. Unfortunately, the "UNKNOW DISK" error message is displayed for a number of reasons...
I replaced the connector on my SMD PCB and now it shows "RAM 8M"
The bad news is that I still cannot get the disk read/write to work. I do believe it is writing, but it simply refuses to read anything. Unfortunately, the "UNKNOW DISK" error message is displayed for a number of reasons...
I'm releasing my disassembly of the SMD v3 BIOS tonight:
http://members.iinet.net.au/~msmcdoug/c ... v3.lst.pdf
Note that it is not complete, and probably contains errors. I am releasing it now because I'm off to Vegas for 2 weeks for work, and won't get any chance to do any more of it for a while. In any case, it's probably complete enough for most diagnostic purposes.
The problem I have with my SMD is that it refuses to read disks. I have tried 3 different drives and 4 different floppies, both 1.44MB and 720KB.
I can format a disk OK. If I examine the floppy disk image on a PC, it looks like what I expect from a blank disk formatted with the SMD. It will wipe disks that previously had data.
Attempting to dump a cartridge results in "UNKNOW DISK" (sic). The odd thing is that I was sure I managed to dump a cartridge a few days ago, and read it in an emulator. But now, I'm not sure how that was possible. Perhaps I was dreaming or extremely tired (or drunk) at the time?
EDIT: Now I recall. It wasn't a floppy dump, but a dump via the parallel cable! Doh!
One part of the disassembly I don't understand is a routine called "check_sig_trk80". It looks to me like it is reading track 80 from the disk and checking against a signature ("FRONT FAREAST COCCL H.K. ") in ROM. It fails with "UNKNOW DISK" if it is not found. This routine is called from quite a few places, basically whenever a disk is first accessed to load/save a file.
What baffles me is that there is no code to write this signature in the ROM?!?
So I'm not sure how any disk access is supposed to work?
I'd appreciate it if anyone could enlighten me on this aspect of the SMD operation? Are special floppies required? Can you read a file from a normal floppy formatted on the PC?
The other possibility is that some sort of hardware error is preventing me from reading a disk. Unfortunately, the "UNKOW DISK" error is also displayed on genuine read errors.
My next step is to patch the BIOS to ignore the signature and see what happens...
http://members.iinet.net.au/~msmcdoug/c ... v3.lst.pdf
Note that it is not complete, and probably contains errors. I am releasing it now because I'm off to Vegas for 2 weeks for work, and won't get any chance to do any more of it for a while. In any case, it's probably complete enough for most diagnostic purposes.
The problem I have with my SMD is that it refuses to read disks. I have tried 3 different drives and 4 different floppies, both 1.44MB and 720KB.
I can format a disk OK. If I examine the floppy disk image on a PC, it looks like what I expect from a blank disk formatted with the SMD. It will wipe disks that previously had data.
Attempting to dump a cartridge results in "UNKNOW DISK" (sic). The odd thing is that I was sure I managed to dump a cartridge a few days ago, and read it in an emulator. But now, I'm not sure how that was possible. Perhaps I was dreaming or extremely tired (or drunk) at the time?
EDIT: Now I recall. It wasn't a floppy dump, but a dump via the parallel cable! Doh!
One part of the disassembly I don't understand is a routine called "check_sig_trk80". It looks to me like it is reading track 80 from the disk and checking against a signature ("FRONT FAREAST COCCL H.K. ") in ROM. It fails with "UNKNOW DISK" if it is not found. This routine is called from quite a few places, basically whenever a disk is first accessed to load/save a file.
What baffles me is that there is no code to write this signature in the ROM?!?
So I'm not sure how any disk access is supposed to work?I'd appreciate it if anyone could enlighten me on this aspect of the SMD operation? Are special floppies required? Can you read a file from a normal floppy formatted on the PC?
The other possibility is that some sort of hardware error is preventing me from reading a disk. Unfortunately, the "UNKOW DISK" error is also displayed on genuine read errors.
My next step is to patch the BIOS to ignore the signature and see what happens...
wow!!!tcdev wrote:I'm releasing my disassembly of the SMD v3 BIOS tonight:
http://members.iinet.net.au/~msmcdoug/c ... v3.lst.pdf
this thread is more and more interesting
no chance you could share the IDA file also ? very handy for debugging...
perhaps you should try another bios too ....
there is at leat 4 bios known : http://www.segaretro.org/Super_Magic_Drive
which chip could I use to burn it ? mainly about speed....
Well, the drive read issue is sorted. But I have no idea why...
I've tried BIOS v3.1g, 3.3 & 4.1. They can all read from the drive no problem.
BIOS v3, the version I disassembled, and which incidentally was installed in my SMD, simply refuses to read disks. Even after I patched out the 'signature' check logic.
It's a mystery. I should note that the BIOS in my SMD was a vanilla 27C128 (with A13 tied high) and no official sticker. Perhaps someone removed a later version of the BIOS and replaced it with v3, which isn't compatible with this hardware (hence the reason they discarded it)?!? That's the only thing I can think of.
BTW any suggestions on which is the "best" version to use? I only went through them quickly, and noticed a "BACKUP TEST" on one of the BIOS images. Should I just use v4.1? Atm I'm using 3.1g. Perhaps there's no real difference in practice. FWIW I'll mainly be using it to load games from floppy disk, as it won't be sitting anywhere near my PC.
I've tried BIOS v3.1g, 3.3 & 4.1. They can all read from the drive no problem.
BIOS v3, the version I disassembled, and which incidentally was installed in my SMD, simply refuses to read disks. Even after I patched out the 'signature' check logic.
It's a mystery. I should note that the BIOS in my SMD was a vanilla 27C128 (with A13 tied high) and no official sticker. Perhaps someone removed a later version of the BIOS and replaced it with v3, which isn't compatible with this hardware (hence the reason they discarded it)?!? That's the only thing I can think of.
BTW any suggestions on which is the "best" version to use? I only went through them quickly, and noticed a "BACKUP TEST" on one of the BIOS images. Should I just use v4.1? Atm I'm using 3.1g. Perhaps there's no real difference in practice. FWIW I'll mainly be using it to load games from floppy disk, as it won't be sitting anywhere near my PC.
good...
in fact, it's why I gave you the link...
I read (somewhere!) the first version of SMD was buggy...but I don't know what part exactly...
for what bios version to use, I don't know....I was looking for one which does RAM test but it doesn't seem to exist (until someone make one!)
I'll try to use Charles test rom until that time
in fact, it's why I gave you the link...
I read (somewhere!) the first version of SMD was buggy...but I don't know what part exactly...
for what bios version to use, I don't know....I was looking for one which does RAM test but it doesn't seem to exist (until someone make one!)
I'll try to use Charles test rom until that time
Oh, I thought you meant disassembling those ROMs, not trying them! Thanks in hindsight!KanedaFr wrote:in fact, it's why I gave you the link...
I read (somewhere!) the first version of SMD was buggy...but I don't know what part exactly...
for what bios version to use, I don't know....I was looking for one which does RAM test but it doesn't seem to exist (until someone make one!)
I'll try to use Charles test rom until that time
The BIOS ROM (8KB) is very full - at least in V3 and I'd imagine more-so in later versions which have more features (eg. supports more floppy drives). There's only a few dozen bytes of free space. So I don't think anyone will be able to include a RAM test.
BTW - and this is completely off-topic and of little interest to anyone - but...
The whole thing that got me started with this was reading an article in Retro Gamer magazine a week or 2 ago about "Mickey Mouse - Castle Of Illusion" (yes, I'm a bit behind on reading it). They waffled on for so long about it that I thought I'd just have to see what the fuss was about.
I fired it up in the emulator just to see if it was going to meet my expectations and I was impressed! I wanted to play through it over the Xmas break on a real console on my 42" LCD TV - but then I found that the DRAM wasn't working (I'd never had the drive working). So I couldn't play anything on it...
A quick search and I found this thread and decided to have a real go at fixing it. But first I had to understand more about it, since I know very little about either the Genesis or the SMD (only picked one up a few years ago completely unexpectedly, and have only played a handful of cartridges on it).
Hence the disassembly, schematics, and as of today - success!!!
Now back to Mickey Mouse...
The whole thing that got me started with this was reading an article in Retro Gamer magazine a week or 2 ago about "Mickey Mouse - Castle Of Illusion" (yes, I'm a bit behind on reading it). They waffled on for so long about it that I thought I'd just have to see what the fuss was about.
I fired it up in the emulator just to see if it was going to meet my expectations and I was impressed! I wanted to play through it over the Xmas break on a real console on my 42" LCD TV - but then I found that the DRAM wasn't working (I'd never had the drive working). So I couldn't play anything on it...
A quick search and I found this thread and decided to have a real go at fixing it. But first I had to understand more about it, since I know very little about either the Genesis or the SMD (only picked one up a few years ago completely unexpectedly, and have only played a handful of cartridges on it).
Hence the disassembly, schematics, and as of today - success!!!
Now back to Mickey Mouse...<http://www.datasheets.org.uk/Scans/Scan ... 38509.html>KanedaFr wrote:I was unable to find the datasheet for the MCCS3201FN....if someone find it, let me know
-
Chilly Willy
- Very interested
- Posts: 2984
- Joined: Fri Aug 17, 2007 9:33 pm
