ULoad

ULoad is a loader system I developed for my Ultima gold cracks. It comes in a few different flavors, to reflect the different needs of the games. It's a IRQ loader, and as such shares traits with the other systems out there such as PlushDOS, DreamLoad, and CovertBitOps Loadersystem. The major feature that sets ULoad apart is the ability to write files, to implement game saves. The system comes in several flavors, to fit the needs of different games.

Commonalities

The loaders share more than a few parts, most notably their ancestry: it all started with an implementation based on Lasse Öörni's rants on IRQ loaders, specifically rants #5, #7, #12, and #13.

They also support writing files, but are limited to overwriting existing files. There is no support for creating new files or changing the file's size.

The drive communication protocol is a 2-bit timed protocol (similar to that in rant #7), which is fairly fast, but there are a few things you have to handle:

• IRQs are be disabled during the transfer of a byte, so any raster effects might be displaced. To compensate, set the IRQ to fire earlier and use cmp $d012 to walk down to the correct line.
• Sprite DMA causes the protocol to fail. Either disable sprites during transfer, or protect them using a raster IRQ.
• NMI during a transfer causes the protocol to fail. Either disable NMIs, or just tell the user to not hit Restore.

They also support the same hardware:

• C64 and C128 (in C64 mode)
• PAL and NTSC machines
• The following drives:
  • 1541 (and compatible clones like Oceanic 118N and Excelerator+)
  • 1570
  • 1571 (both single and double sided mode)
  • 1581
  • CMD FD
  • CMD HD
• SuperCPU
• DTV/DTV2 (though it's known to be unstable for some users)

Model 3

This loader is based on the needs of Ultima 3 Gold. It supports reading of sector chains (e.g. PRG/SEQ/USR files), writing of sector chains, and directory reading. To implement file loading, the computer side has to read (and preferably cache) the directory to get the starting track and sector of each file.

• Small size: the resident part is only 375 bytes.

uloadm3-r1.zip

Model 4

This loader is based on the needs of Ultima 4 Gold. It's an IFFL system, which means that the individual game files are packed into big archives of up to 256 files each. As U4 has nearly 800 files, the loader support multiple IFFL archives, and the scanner stays resident to support re-scanning after changing disks. It also support reading and writing of normal PRG files, for game saving.

• Supports a large number of files.
• Uses a lot of RAM, as it needs three bytes per file for the IFFL tables. In U4 it needs nearly 3 KB of RAM.

ULoad Model 4 is not yet ready for release, contact me if you have a project you want to use it for.

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