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From: "Adam Roman" <aroman@xxxxxxxxxxxxx>
To: "Radek Svagr" <ignor@xxxxxxxxxx> Subject: Re: Re[2]: Booting other OS Date: Thursday, February 10, 2000 6:06 AM Okay, everyone... Get ready for some much
needed hardware info, as well as
some cool ideas! > AR> Hi, Radek. You mean I'm one of
the only ones who has the wonderful
Sharp > AR> service manual for this thing? If it would help, I'd be happy to scan or > AR> photocopy what you need. It's a wonderfully detailed manual. It should > AR> probably be on the FTP for everyone to use (if it ever works). I doubt > AR> Sharp would care. > > I will greatly appreciate if you can scan necessary pages. How many > pages are electrical schematics/how many can you scan? > Also I can give you a fax number which should be free of charge for > you, but scannig it and sharing to all PC3k users is the best idea. The manual is 82 pages long. The schematics
for the 3000 take up six pages,
then there are 2 pages for the top and bottom PCB layout. There are also schematics and board layouts for the CE-301F floppy drive, which uses a now discontinued National Semiconductor DP8473V, but is replacable with a NS PC8477B and probably others. Nothing else is special about the floppy controller board (no custom chips). Perhaps the best part of the manual is the very
detailed discussion of the
hardware, including the custom chips. It's a lot to scan, so it'll take me a few days, but I'd like it to be available to everyone, so I will do it. I won't be able to start until at least Saturday or Sunday, though. I just found out that Adobe PhotoDeluxe, which I
already have installed, can
save in PDF format. I'm not sure how to save multiple scans to one PDF file, but I'll figure it out. I'm still having trouble accessing the ftp with IE
5.0. John Hoh says it's
possible to access it from within newsgroup messages, but I'm not sure how to do that. >
> If there is too much pages to scan, especially I'm interesting in the > circuity around ISA(like) connector, DMA,IRQ controllers and CPU. > Radek, since you have an immediate need for certain info, I can send that to you directly, until I figure the ftp thing out. Would you prefer that I send scans of what you need to you via email or fax? It will probably be well over 1 meg. The info you need is about 18 pages long. > Are there any other details about the ISA-like
connector?
> Yep, lots. The expansion bus is controlled by the SPC ASIC; it is not connected to the CPU. The SPC ASIC controls everything except the LCD and SRAM (which is partially used as video RAM). As seen in the floppy controller schematic, pin 7 must be tied low to enable the expansion connector. Apparently, the expansion connector on an actual CE-301F has a lock switch that physically locks the connector as well as drives this pin low. That is why the gray button under the battery door on the PC3K is not internally connected. They both drive the same SPC pin. There must have been initial problems with this method since the expansion button on the PC3K is pushed in WHILE the connector is being inserted, not after, which would cause excessive noise. To use memory space through the expansion connector, the mapping registers in the SPC must be initialized for the space needed. It is treated as one of the 15 paged memory devices, just like the ROMs, PSRAMs, and slots. In fact, the address and data lines of the expansion connector are shared with all memory devices except for the 128K SRAM. I'm pretty sure that all I/O space not used by the SPC or DVC (LCD controller ASIC) appears on the expansion connector when pin 7 is tied low. Another interresting note... The SPC ASIC
contains a 2-channel sound
controller whose outputs are left unconnected! Imagine, we almost had stereo sound!! The buzzer is actually connected to the output that was intended to be the power control for an audio amp! If anyone wants to experiment with this, the addresses for the control registers are provided. Each channel has 3 digital outputs, maybe for 3-bit D/A using an R-2R resistor ladder or something. Who knows! > > AR> Finally, has anyone ever tried to pop in a 200LX rom in the PC3K? I don't > AR> know anything about the 200, but I'm thinking that just maybe it would work > AR> if the 200 has seperate roms for bios and OS/applications like the PC3K > AR> does. Even though the apps might not work, it might be a way to get a > AR> better dos in there. I have a feeling that there's nothing too wierd about > AR> the PC3K bios, so if a new rom-disk was put in, the OS might work. Do you > AR> know anything about the romable dos's that are out there? Maybe that's > AR> something for us to look into. It wouldn't be hard to stick a new chip in > AR> there if it would solve all of these OS problems. > > Good idea with 200 LX. If there is anybody having contact to a person > having 200 LX please ask if he knows details. At least to make a > bootable SRAM with 5.0 > > Do I remeber well that there is a 27C810 EEPROM in PC3k? (Probably not, > but there is something like this.) > It's a Sharp LH538100 1M x 8 mask rom. But, after much more research, it's not realistic to attempt this, nor is it necessary... Check this out... Because of the very
flexible memory controller in the
SPC, it is actually possible to override the internal roms and map any physical memory space (including that normally used for the BIOS) to RAM or a card slot. After a hard reset, ALL memory space is mapped to the BIOS ROM. The BIOS then sets the mapping up for normal use. By running a special configuration program to change the mapping, a modified PC3K BIOS that supports bootable RAM-drives or cards could be run from RAM or a card (like when a BIOS is shadowed), as well as a different OS ( by disabling ROM-disk C:). Yes, this could actually be done. Trust me. No soldering required. Any 16K page in physical memory space can be mapped to any of 4096 pages of any memory device. The BIOS would also have to be changed to work with the new RAM-BIOS mapping. If someone actually modified the BIOS and wrote the simple configuration utility to change the initial mapping to allow the system to access the RAM-based BIOS, the new BIOS could determine the size of RAM or the card (as it already does) and allow the left over space on that device to be a bootable drive to support the OS of our choice. The configuration utility could be combined with a loader to copy the new BIOS image file to RAM or the card, so by running one file, you have a completely new machine, ready to load and run anyone's favorite OS! Don't worry, soon all the info for this will be
available so you all can
verify this crazy idea for yourselves. It's a lot of work, but it's a definite way to keep these little wonders that we all love so much alive for a long time to come. Anyone out there good at 8088 assembly? ;-) BTW, does anyone know how large a memory card can
be used currently? The
SPC and gate arrays which control the slots output 26 address lines, which is 64 MB (hence the 4096 pages of 16K for each slot). I wonder if the current BIOS supports the entire 64 MB. I imagine it does, but I'm curious. If anyone can help with my ftp problem, I'd
appreciate it so I can upload
the service manual. I don't want to install Netscape to do it, though. Best regards,
Adam Roman |