Dieter, FWIW, according to this Digikey search, TI and Nexperia both list "Active" status for the HCT versions of the '154. And Garth, it seems the AC version is absent, as you suggested.

I like Dieter's solution of using a pair of 138's instead. Also worth considering are the 'HC4514 and 'HC4515 (listed in the search), which are 1-of-16 decoders that feature an input latch you can optionally use. The two chips are identical except the HC4515 has active-high outputs.

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In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

I am curious about the potential for clocking the '816 past 4 MHz in this design. 8 or 12 would be really nice to have as an option.

8 MHz might be possible with 74HC logic. I have my doubts with 12 MHz.

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

Long time ago when I did TV repairs for a living, I had seen a lot of PCBs that had failed due to simple mechanical problems.
It had been cheap PCB material, of course... but better safe than sorry.
If one wants to replace a defective ISA connector, maybe damaged by plugging in a self_built card, he usually would wish to have had wider PCB traces.


Jeff, I'm aware that 74HCT154 is listed as active now.
But nobody could tell if it's still active by the time when Ruud starts populating the PCB with components... or when he tries to build another board of that sort in a few years
//If you do hardware design for a living, >90% of the design might be "dogma and logistics" nowaday.

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

It still can be bought and it doesn't have to this one; any keyboard controller from an PC ATX board most probably will do. I also have some JetKeys laying around.


The VT82C42 and other keyboard controllers are already pre-programmed. I wouldn't mind using a PIC or Atmel if I had sources that go with them. But I didn't even search because I already have the parts.


I agree but again, I have them and other types laying around. As mentioned before, the Eagle schematics are free; you don't like, just change it!


Bit baffled: uhh, why? IMHO 4 kB should be enough to load what ever OS or software you want to use. If needed, the 6522 can be used to bit-bang a SD card. And even then 4 KB should be enough. My personal idea is to use an HDD card in 8- bit mode with a CF card.


I have 020s and 040s laying around as well. 128 KB is a nice value. Unless you have a good reason to use a bigger EEPROM; I always can use some of the I/O pins of the 6522 to swap the various 64 KB blocks.


Have a look at https://jlcpcb.com/. I already used their services.


The original ATX is 9.5"x9.5". My board is smaller.


Why should I? The ATX board is meant to be placed in a PC case. I regularly receive older PCs to scrap for parts so that leaves me with empty cases and power supplies.


I always can make an ISA card with USB functionality. That is the nice thing about ISA. Maybe the average won't find many ISA cards on its way but then, why not making some of your own?


To be honest, I'm not that interested in Ethernet. If I become interested, I'll first have a look at the various 3COM cards I have at home. If that doesn't work out, then I will steal Daryl's work

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This. I worked on the 3Com drivers for NetBSD back in the '90s, and they're not terribly complex. We did everything via direct access, ignoring any ROMs on the board, if they were even present. (The worst part about the drivers were just the tricks to deal with bugs on certain revisions of the boards, but all that is in the freely available source code so you'll at least know what the problems and their solutions are.)


Having recently watched the video The Extreme importance of PC Board Stack-up (recently posted by BigEd), I now know that you do not want to separate a signal layer from its ground plane by a +5V plane. :-)

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Curt J. Sampson - github.com/0cjs

If you look at the Micro-PET, I am working on VGA timing, and in SPI interface, included in a single CPLD.

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Author of the GeckOS multitasking operating system, the usb65 stack, designer of the Micro-PET and many more 6502 content: http://6502.org/users/andre/

I like your project. I had started a project using an PC ISA backplane for much the same reason. A couple of things I shoot about. Could you reduce the number of slots? Most modern PCs have fewer than eight slots. I don’t think I ever used all the slots in the PC. Could the bus be faster with fewer slots to drive? After a VGA card, audio card, and disk, what is there (these could also all be on one card these days)? How about providing for some of Garth’s ram modules (or other ram modules) on the motherboard?

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http://www.finitron.ca