Hi, I am also getting into my p-System again on TI-99/4a and SNUG SGCPU. It'd be great to discuss ideas with others enthusiastic about this card. I tried getting the OS disks to run from my RAM Disk (Horizon clone), but after looking at the ROS DSR, I think it arbitrarily writes to CPU RAM locations and corrupts the p-Systems memory space, so will need some modification. It'd also be great to get it working with the SNUG SCSI2 interface.
Maybe it's possible to make the p-System ROMS/GROMS run from the SNUG HSGPL card, so I can save a slot in my PEB.
Dragonstomper, how was the book?
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#77 OFFLINE
apersson850
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Star Raider
Posted Mon Apr 16, 2012 8:29 AM
Doesn't sound too likely that the RAMdisk writes to random locations in the computer's memory, since that would most likely ruin not only the p-system, but other software too.
I made my own RAMdisk for my p-system, so of course I made a driver which would behave. But a friend had a RAMdisk from a commercial vendor, and we got that running too. I'm not sure about the brand, though. Maybe Horizon. Did CorComp sell RAMdisks too?
The p-system in general is prepared for six drives, but TI only enabled their version for three, since their drive controller card didn't support any more than that. So you have to modify some system tables to make additional drives work. I run my system with four physical 5 1/4" drives and one RAMdisk, so that's doable, for sure.
I made my own RAMdisk for my p-system, so of course I made a driver which would behave. But a friend had a RAMdisk from a commercial vendor, and we got that running too. I'm not sure about the brand, though. Maybe Horizon. Did CorComp sell RAMdisks too?
The p-system in general is prepared for six drives, but TI only enabled their version for three, since their drive controller card didn't support any more than that. So you have to modify some system tables to make additional drives work. I run my system with four physical 5 1/4" drives and one RAMdisk, so that's doable, for sure.
#78 OFFLINE
apersson850
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- 84 posts
Star Raider
Posted Wed Apr 18, 2012 12:29 AM
I should perhaps add that my RAM-disk driver supports only the subprogram to read and write sectors on the disk. That works fine, so that prooves that nothing else is needed by the disk system to support the p-system. Just ship data to and from the normal sector buffer in the machine.
The p-system accesses disks in chunks of blocks, which are 512 bytes long, but the BIOS part in the PME translates that to two 256 byte sector accesses, so that's nothing the disk memory system needs to account for.
Formatting I do separately, using an assembly program I linked into my own dformat.code.
The p-system accesses disks in chunks of blocks, which are 512 bytes long, but the BIOS part in the PME translates that to two 256 byte sector accesses, so that's nothing the disk memory system needs to account for.
Formatting I do separately, using an assembly program I linked into my own dformat.code.
Edited by apersson850, Wed Apr 18, 2012 12:30 AM.
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