20 June 2021, 10:16 | #181 |
Mighty Pirate
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It does, if it works as we intended.
I have created a project page on Hackaday where we will post further updates as testing progresses. @Mathesar: I think you were involved in the development of the Gary adapter for PeteAU's RAM expansion board. Would you be interested in working on the next version of Raemixx? I have a few ideas but I'm not that much into the Amiga memory architecture. Last edited by SukkoPera; 20 June 2021 at 18:07. |
20 June 2021, 20:16 | #182 | |
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20 June 2021, 23:31 | #183 |
Mighty Pirate
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Thanks a lot. I'll get back to you after we are finished with the testing for V2. Maybe you can join the project page on hackaday in the meantime, as that should also give us some means of communication.
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21 June 2021, 18:29 | #184 | |
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I first have to finish and release the 14MHz accelerator. Next up will be to build an SD-box (http://eab.abime.net/showthread.php?t=102642) as I can't use my internal IDE anymore once the accelerator is installed. |
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21 June 2021, 19:08 | #185 |
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Sure, take your time . SDBox works very well by the way!
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16 July 2021, 22:33 | #186 |
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I built one with Tmtech T224162B-35J DRAM in sockets, it worked fine so you can add them to the supported DRAM list
Late edit: I also note that my A600 Rev 2D has HM514260JP8 by Hitachi so they probably would work fine too. Last edited by Per Hansson; 17 July 2021 at 13:06. |
19 July 2021, 19:56 | #187 |
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Looks great
If somebody knows where i can find (cheap) such sockets for SOJ-42 please let me know. Seems SOJ-42 sockets are rare as hell. |
21 July 2021, 22:22 | #188 |
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Fantastic Have ever considered (or if it's even possible) designing the ports to be modular? The large space in the lower corner of the pcb, could possibly accommodate the different, breakaway module pcbs. Probably too much work
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24 July 2021, 21:27 | #189 | |
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I tried slowing the edges of the CCK down by adding some capacitance to the pin. Although it did help reducing the amplitude of the crosstalk, it also made the crosstalk a little wider e.g. lower in frequency. Thus instead of having few strong jailbars I ended up with many less strong jailbars. Also, the EMC filter on pin15 also slows the signal down a little as it contains a capacitor already. The best solution is thus probably a series terminator resistor right after the '245 driver (u41). To be continued... |
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25 July 2021, 21:48 | #190 |
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Did some more experimentation on the CCK signal. Terminating pin 15 of the video connector with a 220pF/100ohms series network ("snubber") yields the best result on my setup. Instead of some very visible jailbars (the LCD screen has to sample the "wiggle" on the green/red channels just right for the bars to become visible) I now have many/regular bars that are just barely visible.
Best solution would still be to slow down the CCK with a series termination resistor though. I haven't tried it yet as it requires modding my motherboard. Another thing I want to have a look at is the skew between red, green and blue. I notice some colored lines near some high contrast edges and maybe we can fix those as well. |
28 July 2021, 04:24 | #191 | |
Golden Boy
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thanks, great contribution! please let me share my findings tested with LCD and CRT Last edited by kinmami; 28 July 2021 at 04:40. Reason: important note to add |
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28 July 2021, 08:14 | #192 | |
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However, I think there is confusion about the exact mechanism of the jailbars. "terminating an unterminated line" suggests the issue is radiation, like the CCK line acts as an antenna. Maybe it does as well but I *think* the main mechanism is capacitive coupling between the CCK line and the red and green channels. This parasitic capacitor (it's probably in the connector but it could also be on the PCB if the CCK trace runs close to the red and green trace) is very small so only fast edges of the CCK line can couple in. The 47 Ohm resistor slows down the driver so much that the edges of the CCK signal become slow enough to cause less trouble. BTW, is that something you observed as well, than it does not occur on the blue channel? Would be interesting to know. I also checked using DPaint by creating red, green and blue screens and I could not see the jailbars on the blue screen. I could also confirm that using the scope. I will try to post some screenshots here. PS, I'll comment here because as much as I like hackaday, I cannot really get used to *hackaday.io* |
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28 July 2021, 08:57 | #193 | |
Golden Boy
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Jail bars are more intense on R and G patterns compared to B. Displaying colour gradients from full black to full white (a complete palette set), there are few cases in which B line turns to be noisy (affected by persistent jail bars) as well. Termination of ext clock or even better the disconnection of the unbuffered CCK solve the issue (at least on my display equipment). The use of additional L-R (inductive-resistive) beads on RGB helps to cut High Freq noise. The C-R (capacitive-resistive) common-mode beads E431-432-433 are not so powerful at HF domain. Last edited by kinmami; 28 July 2021 at 09:03. Reason: important note to add |
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28 July 2021, 14:34 | #194 | |
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Although the Amiga 500 schematic suggests differently, on my system E431,432,433 are loaded with ferrite beads (L-R). However, they are indeed not very good (only "half" a winding) and on the wrong side of the parasitic capacitance. Your solution of placing them in the VGA adapter is the right place (after the DB23 connector). Also, the SMD beads you use probably have far better specs. I agree with you about the CCK, disconnection at U41 is by far the best solution. However, it also kills compatibility with a genlock. For the RAMIXX500 it could maybe be done by a jumper? Or a small network consisting of a bead/resistor and a small capacitance right at the source which is the output of U41. That would retain compatbility with a genlock while still keeping the jailbars out of sight. At least, that is what I hope, it has to be tested first... But as we are maximizing the video quality, shall we fix this as well: Maybe you have seen it as well. It annoys the hell out of me. While I can accept that the image is not razor sharp because of the resampling by the LCD screen, I cannot accept these colored fringe lines. I have found that these colored fringe lines are caused by skew between Denise's red, green, and blue channels: What could we do about this? The delay for green is up to 4ns. Too long to compensate for by a longer trace. It might also differ among Denise versions/samples. Maybe the best solution is to resample using a 14MHz clock... Could be done on an improved vidiot or right on the motherboard. Last edited by Mathesar; 28 July 2021 at 15:41. |
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28 July 2021, 16:50 | #195 | ||
Golden Boy
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good points here in your discussion:
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I need to think about it and see what we can do for the V3/new vidiot. |
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28 July 2021, 21:44 | #196 |
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I must add that my 500 is an early rev.5 with a 8362R8. As the ramixx500 is an A500+ one would equip it with an 8373 hires Denise right? So I started digging and found one in my stash of components. So I did the test again and the skew is less on the hires Denise. About 2ns total instead of ~6ns. Visually the image quality is also better although one can still see some visible color edges. I guess it also depends on the monitor. Mine is a NEC EA231wmi. To reclock the signal for a hires Denise is not easy as you'd need a 28MHz hires clock which is not readily available.
Edit: Random thought: Using 0,1mm wide traces and 0,1mm spacing one can fit ~0,5m of length on 1 square cm. Enough for about 2,5ns of delay.... I am going to sleep now Last edited by Mathesar; 28 July 2021 at 22:10. |
29 July 2021, 08:49 | #197 |
Golden Boy
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21 November 2022, 23:33 | #198 |
Golden Boy
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Hello
I have designed and shared this adapter lately Commodore Amiga DB23 RGB VGA External Video Buffer (V6) it implements the THS7316 video amp for a perfect RGB equalization and filtering (100% jail bars removal). |
22 November 2022, 02:19 | #199 | |
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Nice work - thanks for releasing it publically |
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01 December 2022, 02:42 | #200 |
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