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  • sergey's Avatar
    November 16th, 2017, 09:12 AM
    Resistor is not needed (but won't hurt), just disconnect TVGA ALE pin from ISA, and connect it to +5V. I don't think it is something that a...
    54 replies | 5321 view(s)
  • sergey's Avatar
    November 16th, 2017, 09:03 AM
    Huh, tested this on the boards I have available: IBM PC, IBM XT, PC-Retro, a chipset-based Turbo XT, 286-AT, and it works perfectly. Apparently...
    54 replies | 5321 view(s)
  • sergey's Avatar
    November 14th, 2017, 09:59 PM
    sergey replied to a thread Victor V86P in Handhelds/Portables
    The Chips and Technologies F82C100 chipset looks very interesting. I looked through the datasheet, but unfortunately it doesn't offer some details....
    2 replies | 358 view(s)
  • sergey's Avatar
    November 11th, 2017, 01:23 AM
    I implemented an easier approach - it only uses ALE and AEN signals. I believe this approach is also more reliable. It doesn't change ALE (other...
    54 replies | 5321 view(s)
  • sergey's Avatar
    November 11th, 2017, 01:01 AM
    I've prototyped and tested my circuit. It works nicely with original IBM PC, PC-Retro, and IBM XT boards. It also works with a chipset based XT clone...
    54 replies | 5321 view(s)
  • sergey's Avatar
    November 10th, 2017, 11:39 AM
    Here is what I came up with. Haven't tested it yet though: It should work as follows: - If AEN is low (inactive, no DMA operation), it...
    54 replies | 5321 view(s)
  • sergey's Avatar
    November 9th, 2017, 11:50 PM
    So, I tested the original IBM XT board, and it is not working with any of the Trident TVGA cards I have (TVGA8900CL, TVGA8900D, TVGA9000A,...
    54 replies | 5321 view(s)
  • sergey's Avatar
    November 9th, 2017, 11:44 PM
    Trident TVGA8900* and TVGA9000* cards will not work in the original IBM PC, the original IBM XT, and some clones. This is because these cards rely on...
    32 replies | 32606 view(s)
  • sergey's Avatar
    November 9th, 2017, 05:30 PM
    Good question. Faraday FE2010/FE2010A chipset specifically has two separate ALE signals: one that goes to the address latches (ALE), and one that...
    54 replies | 5321 view(s)
  • sergey's Avatar
    November 9th, 2017, 09:42 AM
    Yes, tried the same yesterday evening, doesn't seem to help :-(
    54 replies | 5321 view(s)
  • sergey's Avatar
    November 9th, 2017, 09:37 AM
    Right, /AEN and CEN do not affect ALE signal. And I think that's exactly why it is being generated during DMA. As I explained above, for DMA...
    54 replies | 5321 view(s)
  • sergey's Avatar
    November 8th, 2017, 02:02 PM
    Right... It might be a bad picture ;-) I've seen ALE pulsing while DMA was outputting the address as well. The image below shows ALE and AEN (which...
    54 replies | 5321 view(s)
  • sergey's Avatar
    November 8th, 2017, 09:50 AM
    Still, I am pretty much confused why Trident TVGA cards work fine on IBM XT and don't work on IBM PC. Yesterday evening I fetched the original IBM...
    54 replies | 5321 view(s)
  • sergey's Avatar
    November 7th, 2017, 12:17 PM
    But it works on most XT's, including the original IBM XT ;-) And I am not quite sure what is broken on my XT... Can you elaborate?
    54 replies | 5321 view(s)
  • sergey's Avatar
    November 7th, 2017, 09:12 AM
    Nice work! I think it all can be implemented in a single SPLD...
    54 replies | 5321 view(s)
  • sergey's Avatar
    November 7th, 2017, 08:30 AM
    Actually, on both IBM PC and IBM XT all DMA cycles, not only memory refresh cycles, are performed this way - by inserting wait cycles to stop the...
    54 replies | 5321 view(s)
  • sergey's Avatar
    November 7th, 2017, 07:23 AM
    Fixed that, also added a note about IBM PC not working...
    54 replies | 5321 view(s)
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