Transwarp v0.84 – 50x fastload system on plain vanilla stock 1541 (use with C64) | Hacker News Reader

Transwarp v0.84 – 50x fastload system on plain vanilla stock 1541 (use with C64)

csdb.dk

46 pointssandebert10 comments

These typically work by changing the media bit encoding to be easier to process with 6502 instructions instead of a lookup table. Others simplify the table and use more RAM so that fewer lookups are needed. I haven’t looked at how Transwarp works yet but it seems like the latter.

Some discussion with the author: https://www.lemon64.com/forum/viewtopic.php?t=78558&start=0

There’s a newer version here: https://csdb.dk/release/?id=214786

Release notes: https://csdb.dk/release/?id=214786&show=notes#notes

More details from another advanced loader:

https://www.linusakesson.net/programming/gcr-decoding/index.... https://www.linusakesson.net/software/spindle/v3.php

Amazing. It should be noted that 50x faster is 20KBps, the original 1541 firmware was stupendously crippled. Loading the entire C64 memory space in 4 seconds is a tremendous quality of life improvement for a C64 user. Heck, you can read the entire disk in less than 9 seconds.

Any explanation of how it works?

Something here: https://www.c64-wiki.com/wiki/Transwarp

Also: "Plain Commodore GCR encodes 4 bytes raw to 5 bytes on disk, Transwarp encodes 3.5 bytes raw to 5 bytes on disk. (Thus only 223 = $df instead of 256 bytes per block, the 224th byte is the checksum.)

One trick is to encode those 3.5 bytes using a subset of plain Commodore GCR, such that it works just fine with d64 and regular transfer/copy solutions. Part of that trick is that decoding a GCR byte drive-side just takes a table lookup (4 cycles). =)"

There is a lengthy thread with some technical details attached to the original v0.64 release (late November 2020): https://csdb.dk/forums/?roomid=12&topicid=146327

The core scheme hasn't changed much since then. =)

And it's at least 100x cooler than most fastloaders, because it is Open Source (GPLv3 or later).

This isn't just "yet another fastloader". :)

>edit: It's actually open source!

I haven't looked at it but I bet it's written in handwritten ASM. You can disassemble that. It probably won't be easy but with a memory map of the C64 and 1541 you could tell how it's working and learn from it.

I just checked the newest release on csdb and it has a .s source file you can download. It is released under the GPL. :)

Wish granted: https://csdb.dk/release/download.php?id=260085

It's even GPL.

And so is the new version: https://csdb.dk/release/download.php?id=264898

I couldn't find it when I searched earlier, but it's there in plain sight, among the other downloads!

I 100% expected a link to a git repo. Google was also, as usual, useless.

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