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386 SBC by Alexandru Groza https://oldcomp.cz/viewtopic.php?f=57&t=9219 |
Stránka 5 z 21 |
Autor: | Александр [ 30.08.2021, 17:50 ] |
Předmět příspěvku: | Re: 386 SBC by Alexandru Groza |
OK, thanks for the answer. |
Autor: | Александр [ 30.08.2021, 19:14 ] |
Předmět příspěvku: | Re: 386 SBC by Alexandru Groza |
Current state of the project vs previous built xi8088. |
Autor: | Marty [ 31.08.2021, 21:30 ] |
Předmět příspěvku: | Re: 386 SBC by Alexandru Groza |
Same here, I did not find one yet. However I was in touch with somebody that perhaps knew of some replacement, so I will definitely let you know here if something relevant is found. |
Autor: | Martin8bity [ 04.09.2021, 17:30 ] |
Předmět příspěvku: | Re: 386 SBC by Alexandru Groza |
Александр píše: May you please share workable bios image? Send me your e-mail to PM. |
Autor: | Александр [ 05.09.2021, 21:57 ] |
Předmět příspěvku: | Re: 386 SBC by Alexandru Groza |
Looks I found an analog of rft vqb37 on ebay, but it here is too expensive as for me. https://www.ebay.com/itm/283974850597 |
Autor: | Александр [ 14.09.2021, 11:11 ] |
Předmět příspěvku: | Re: 386 SBC by Alexandru Groza |
Let's start. |
Autor: | Александр [ 20.09.2021, 17:09 ] |
Předmět příspěvku: | Re: 386 SBC by Alexandru Groza |
We have found an issue. Resistance of R19 have to be 22Ohm, to provide 0.4 V of logical zero. Currently it provided 1.5V, and it is out of TTL specs. Please make this change, in case if no reset button functionality. |
Autor: | Martin8bity [ 21.09.2021, 10:23 ] |
Předmět příspěvku: | Re: 386 SBC by Alexandru Groza |
Александр píše: We have found an issue. Resistance of R19 have to be 22Ohm, to provide 0.4 V of logical zero. Currently it provided 1.5V, and it is out of TTL specs. Please make this change, in case if no reset button functionality. You are right, I actually replaced it by wire some time ago It could be better to increase the value of R20 to 1k5. I do not think there is so strong pullup (330R) needed. It would change the reset time constant, but it is quite low, so it should not be a problem. The very low pullup is possibly there to prevent disturbances on the quite long reset wire that goes all over the board to IC24. |
Autor: | Martin8bity [ 21.09.2021, 15:31 ] |
Předmět příspěvku: | Re: 386 SBC by Alexandru Groza |
Did your friend got it to work? |
Autor: | Martin8bity [ 21.09.2021, 18:00 ] |
Předmět příspěvku: | Re: 386 SBC by Alexandru Groza |
By chipset you mean both, the OPTi 82C495XLC and 82C206? If all clocks are OK it has to be some control signal around the chipset. There are plenty, but I am afraid you will not move without checking everything. |
Autor: | Александр [ 21.09.2021, 18:06 ] |
Předmět příspěvku: | Re: 386 SBC by Alexandru Groza |
Currently he checked mostly 82c495xlc and neighbors, 82c206 was swapped with another one, but not completely checked yet, including connections between both ic's. |
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