This is my version of DolphinDOS 3 PCB targeted for C128DCR. With a 40-wire IDC ribbon cable it can work with any 1541/71 drive. But this version is meant to be plugged directly into U101 (6502) socket so that it would neatly fit under the 1571 drive mechanism.
Based on the work of SilverDream! redrawn in KiCad: https://e4aws.silverdr.com/projects/dolphindos3/
PCBs are with me already and I have all the parts. If this works, everything will be published on GitHub.
Stay tuned!
The circuit is simple. Three are not too many parts, but a lot of soldering points. The work took me about 1h.
It should fit into 6502 socket inside C128DCR without extension cable so I will omit 40 pin IDC cable socket.
This looks like unfinished IDE ATA interface.
In the next step I had to desolder 6502 that controls the 1571 and replace it with a socket.
I added fresh solder from the bottom and then used desoldering tool to remove it. It's never enough to free all the chip's legs, so then I used hot air from the top side.
On the right a part of my earlier 1571CR RAM expansion is visible. This will be removed - DD3 board has the same function.
Here is the earlier project if you're interested: https://github.com/ytmytm/c128-bytewide-color-ram-1571cr-expansion
A daughterboard to expand C128/D/DCR color ram to 8 bits and/or to 32K OR expand internal 1571 RAM - ytmytm/c128-bytewide-color-ram-1571cr-expansion
6502 survived and the drive works: w/o 40pin ribbon!
Now I need a break. I have to prepare ROM images and a parallel cable to test if DD3 actually works.
The daugtherboard will have two switchable 32K ROMs: DD3 and JiffyDOS patched to use extra RAM as a track cache: https://github.com/ytmytm/1571-TrackCacheROM
It's not as fast as DD3 but I will use JiffyDOS across other devices (SD2IEC/UII+).
I need to do the same for U32 Kernal ROM for both 128 and 64 modes too.
Parallel cable was the next step. The IDC connector end doesn't have strain relief because then I wouldn't be able to push it through user port opening while the mainboard is in.
The connector is easy to make, but with symmetrical plugs I'm never sure what am I looking at on the drawing. Photo for reference (also for me). Side with one wire is up, side with 9 wires with red on the left is bottom.
Great success - it works! The biggest surprise is that the file name of the only DolphinDOS 3 1571 drive ROM I found suggested it's for a standalone 1571. However after testing in VICE it worked in C128DCR. This finally confirms that indeed that ROM is good for 1571CR.
That is a bit strange because both original Commodore DOS ROMs as well as JiffyDOS images have different versions for standalone 1571 and 1571 from C128DCR.
Just how fast is it?
31 times as fast as stock 1541. Faster than DD3 on 1541 (23x).
Here are the full benchmark results from both 1571 mode (U0>M1) and 1541 mode (U0>M0) using 64'er benchmark program from https://www.c64-wiki.com/wiki/Comparison_of_fast_loaders
What a day!
In case tomorrow I get hit by a bus I have already published everything on GitHub. It was quite difficult to find both C128 and 1571 DolphinDOS firmware parts. Now there is one more place that preserves them together.
The README file will be gradually updated with proper links and pictures.
ytm
