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Post by eslapion on Jul 23, 2016 3:31:13 GMT
I have had a C128 since 2006 but I do so incredibly little with it.
There are dozens of things I can think of doing with it but never got to it.
The first thing I would like to do is develop an RGBi to S-Video adapter using the newly acquired knowledge from the investigation of the 6561 by lance.ewing on the Denial forum. Now I have a pretty good idea how the VIC-I/II generated the color signal.
Another thing I would like to do is a PLA tester which is fast enough and checks all 65536 possible combinations.
Worth mentioning, I also have a 1581 and 1571 drives which can help take advantage of this nice machine.
A drawback, my 128 only has 16k of VDC DRAM but since I know it only requires changing the 41416 to 41464 to get to 64k, I will probably do it when I feel brave enough.
Also, I noted that when the 128 is in 64 mode, it is possible to push the CPU to 2MHz mode during the blanking intervals and a few games take advantage of this. I have noted Gunship and Stealth Fighter but I guess there are others.
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Post by mrbombermillzy on Jul 23, 2016 20:41:46 GMT
You can forget anything about the PAL/NTSC VICIIe video system for the RGBI output. Its more like (well pretty much exactly, apart from the brown/dark yellow) the IBM CGA digital out from the 9 pin din DB-9 connector.
However, do have a go and experiment with the machine. Especially the 8563 VDC! :-)
I would HIGHLY recommend that you dont desolder the VDC ram, as its much easier to just plug in an upgrade kit without having to solder anything.
There are a few people round here who are starting to really get the ball rolling with some new and very interesting projects for the 128. I have left detailed instructions in another thread on how to increase the native resolution to a possible 1024x592i resolution if you have the right monitor. There are also other video tricks by others which can display VGA output (once converted to RGB analog) and VICIIe interlace modes.
There are also new cartidge projects and various bits and bobs being done. An interesting time to own a C128, i think. :-)
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Post by eslapion on Jul 23, 2016 21:54:19 GMT
You can forget anything about the PAL/NTSC VICIIe video system for the RGBI output. Its more like (well pretty much exactly, apart from the brown/dark yellow) the IBM CGA digital out from the 9 pin din DB-9 connector. Yeah, I took a look at the schematic for RGBi to RGB converters as well as the converter inside the C128 which generates the monochrome 80 col. output. I am quite confident I can design a luma+sync source of good quality. The VDC output remains a 15KHz signal which is compatible with NTSC or PAL TV systems with regards to timing. Generating the color signal may prove more difficult but I noticed the VIC-I and VIC-II simply use a set of 4 digital signals of 3.579MHz (in the case of NTSC) each phase shifted by 90 degrees then double integrated to convert them to sine waves. For each color displayed one or two of these phase shifted signals is mixed then amplitude adjusted. Converting RGBi to this color mix can probably be achieved with a single 74LVC4066. I will but hardware fidgeting just for the sake of hardware fidgeting has its limits. I really have 2 important applications in mind: - Dumping G64 files to 1571 to regenerate a few originals; the Zoomfloppy adapter refuses to work with my french Canadian laptop!! - Testing PLAs and/or clones thereof. Since I solder/desolder chips from various Commodore equipment on a weekly basis using professional tools, I have to ask if there is something particularly different with this specific type of intervention that could turn it into a mess. Is there a nasty surprise waiting for me at some point I should be made aware of? Very interesting! The ability to have 2MHz on time slices in C64 mode is attractive too. I suppose there must be a way to have interlace in C64 mode too. Very interesting too!
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Post by ken on Jul 23, 2016 23:29:37 GMT
I guess I need to be extremely careful how I word this so I don't get miss quotes as saying something I did not say in general terms and in my own opinion ...... the 128 is a bit harder to desolder parts from than a vic20 or c64 I only say that due to what I myself have seen when fixing hundreds upon hundreds of systems the 128 in my opinion seem to have all the legs of the chips (bent) and ground down , same as what you will find on a few c64 boards to me ..... that makes it a bit harder to unsolder chips from the board that being said ...... anyone who can properly run a soldering iron will have no issues, it just takes a little more time I should add that 99.9% of the systems I have worked on were NTSC....I can not speak of how the PAL systems were manufactured I also remove the chips intact, if you are cutting/snipping the legs off before desoldering, you will have no issues at all
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Post by mrbombermillzy on Jul 24, 2016 0:09:01 GMT
Is there an reason that you would want s-video instead of an analog rgb signal? A digital to analog rgb conversion circuit would be much simpler and a higher quality than what you propose to do and would be simpler as it wouldnt require any colourburst signal.
Regarding the 64kb upgrade; I would have thought that plugging in a piggyback board would be much less of a risk than desoldering IC's off a mainboard. No matter how minimal the risk, there is always something that could go wrong. Also, you could upgrade to a 8568 which is a slightly better option anyway.
You mention fidgeting for the sake of it. Well, the VDC chip is known to have issues with character display corruption in screen widths above 80 characters. The chip was meant to have programmable screen widths (including more than 80 columns) so there is something else wrong here. I believe it to be the video ram bandwidth and will hopefully (eventually) get to the bottom of it.
If you really want to get the max from 2mhz mode, you could design a clever section of assembly code which contains valid screen data so when the vic reads what is left on the system bus at 2mhz it wont just display garbage. I believe this may have been used in parts of the RFO demo.
For G64 images, you need nibtools and the parallel xp1541 cable.
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Post by eslapion on Jul 24, 2016 0:16:55 GMT
the 128 in my opinion seem to have all the legs of the chips (bent) and ground down , same as what you will find on a few c64 boards to me ..... that makes it a bit harder to unsolder chips from the board Ouch! I encountered the same problem with a C64c (250469) board recently. I managed but it was quite unpleasant. Thanks for the warning. My C128 is NTSC. I am in Canada. Is there an reason that you would want s-video instead of an analog rgb signal? A digital to analog rgb conversion circuit would be much simpler and a higher quality than what you propose to do with colourburst signals. Yeah, there are multiple reasons. I already have a RGBi to RGB converter I use along with an Ambery AV1 and the result is blurry! I know the problem is not with the Ambery because I used it in the past with an A500 and the image was perfect. So I told myself since I now have a flat panel RGB monitor which turns out to support RGB @ 15KHz (and that rendered the Ambery useless with the Amiga 500), why not connect the RGB analog output from the RGBi converter directly without the Ambery? The monitor displays nothing! I suspect that's because the RGBi to RGB converter also performs a logical operation on the H and V syncs to combine them. Also, considering what I learned about the insides of the VIC-I and VIC-II and how they internally convert a digital color value into an analog signal, I see it as a bit of a challenge to turn a 4 bit digital signal (6 bits if you count the syncs) into a TV signal of decent quality. I consider the VDC extra RAM board seriously. I only have one C128 and I don't want to damage it. What is a 8568? That's not familiar to me. I assume using DRAM rated faster than the default 120ns is not going to fix this one. Whoa... this one is way above my feeble little understanding of the C128. Maybe one day. Oh no! This is exactly what I want to avoid! I may be a naive idealist but I tell myself if the 1571 can receive data at about 40kB/sec with the Zoomfloppy with no extra RAM and no special cable, there must be a way for the C128 to send data just as fast, assuming the computer takes a little break to organize the data between each track. Even if I had the XP1541 cable, I would have nowhere to plug it. The reason why I can't use Zoomfloppy is because the software provided with it will not work on a french-canadian version of Win7-Win10 which is what's installed in my i7 laptop. There isn't a parallel port on an i7 laptop. There isn't a parallel port on any PC sold since about 2008.
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Post by eslapion on Jul 24, 2016 1:20:30 GMT
Forgot to mention: I'd need the services of a decent programmer to assist with the PLA tester.
Mostly I need to know how to attach a pair of 74LS273 flip-flop to the IO lines and how to "poke" them from BASIC.
Checking a PLA always involves checking 65536 values and that's too much for the VIC-20 or C64.
Added edit: a single 6522 VIA plugged to IO1 or IO2 may be used in place of the pair of LS273.
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Post by Zippy Zapp on Jul 24, 2016 5:13:28 GMT
For G64 images, you need nibtools and the parallel xp1541 cable. With a Zoomfloppy you can use nibtools with a 1571 and a serial cable for G64 images. No parallel cable needed. From the manual:
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Post by eslapion on Jul 24, 2016 7:04:33 GMT
With a Zoomfloppy you can use nibtools with a 1571 and a serial cable for G64 images. No parallel cable needed. From the manual: Yeah but... as I said above... This begs the question, if the 1571 drive can receive (and save) using the high-speed serial nibbling, can't the C128 send the data using this same method instead of a Zoomfloppy ? What I want is a software solution to take a G64 image that's on a 1581 disk and save it to a 1571 using that method.
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Post by mrbombermillzy on Jul 24, 2016 17:44:58 GMT
Cant really help with your PLA query or the serial transfer speed as Ive never had an external burst mode drive to tinker about with.
The 8568 is the 'improved' version of the 8563 VDC. It was standard on the C128 DCR and some plastic case 128D's. It eliminated some glue logic, came fully populated with 64kb ram and included some little improvements like a reverse polarity setting for the sync for an EGA compatible output. Its also not pin compatible with the '63.
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