| Electronics > Beginners |
| modern TTL/Logic-gate/74xx |
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| ker2x:
Friendly greetings ! I'm a beginner with hardware project (my last circuit board was 30 years ago), and "slightly" obsessed with CPU design, Compiler design, OS development, ... (well, i'm an IT engineer). I'm currently designing, in software, my own cpu, emulator, os, assembler, BASIC. (in fortran, because that's how i roll (i may switch to C/C++/C# for the compiler)). of course i want to do it in hardware too, because why not ? (well, that would require to switch to a 8 bit CPU but i don't mind). I played with FPGA, but it's too much of a pain, i just don't get it. (beside, VHDL look like ADA and i have a massive PTSD with ADA.) I will, of course, implement the design in logisim first, then on a circuit board emulator, then, hopefully, in hardware. And i totally want to design the PCB, it will be 99% of the fun for me. However, i checked a lot of video, tutorials, sources, etc... and it's all good old 74xx, massive chips with 2 or 4 gates. Are there modern highly integrated surface mounted TTL chips ? (with dozens of gate per chips) I don't want to solder it, i'll just send the files to a PCB Prototyping Company (JLCPCB & co) so SMT is the way to go (much cheaper, right ?). Is there a list ? a reference website ? a reliable source ? I want at least a rough idea of the kind of chipset i can use, read the datasheets, etc. I'll design the cpu based on the available hardware (i also have a 32 bits design in progress but it will be 100% emulated in software and pretty much impossible to replicate in hardware (eg: complex number ALU)) I'm super early in the process, i'm just exploring the whole stuff in order to get the idea of what's ahead. Thanks to eevblog i have a rough idea of how difficult it is to complete a full project. I considered, since many years, to do easier projects but there are no other project that interest me. Believe me, i tried. But nope, CPU or bust ! I may do a "modular" CPU just so i can create multiple PCB and if i fail i'll just have to redesign a single PCB (with less chips) instead of the probably expensive full CPU for every countless mistake i'll make. Thank you ! Super important PS : - It's useless to tell me to give up, even if you're 100% sure that i'll fail : just let me enjoy the process and the magic smoke. i'll still learn anyway. - When i write "cpu" : it will be a working computer. But i'll just use whatever microcontroller available for the non-cpu part of the computer (eg : a pic board, arduino, raspberry pi, or even an fpga with an soft-cpu ip core... anything easily programmable with serial<->usb communication and enough I/O). And it will be easier that way to test the "sub-pcb" piece by piece (i do have an oscilloscope and logic analyzer if needed) |
| oPossum:
--- Quote from: ker2x on October 07, 2019, 04:50:42 pm ---Are there modern highly integrated surface mounted TTL chips ? (with dozens of gate per chips) --- End quote --- I think this is as close as you will get to that... https://www.microchip.com/ParamChartSearch/chart.aspx?branchID=30024 |
| ker2x:
I'll just add some bonus question here : Thanks to my painful experience with FPGA i have a rough idea of the importance and difficulty of timing. I'm planning to have massive safety margin and make the cpu run super slowly, i'll be happy with a few KHz (or is it too much already ?) And thanks to the multi-board design it will have absurdly long trace (and potentially EM sensitive wire too) so high clock speed (1+ Mhz) is probably impossible anyway Bonus question N°1 : But being slow come with problems too, it seems. how slow can it be ? The only thing i know is that some type of ram need to be refreshed and that's it. I have ZERO idea of the potential problems that can come with a slow clock. So any random tought about it are much welcome. Bonus question N°2 : Can i just use my whatever-glue-microcontroller to handle the clock ? (Since i'll have one for sure to emulate the non-cpu part of the computer) Bonus question N°3 : the memory isn't technically part of the CPU (except the registers), should i use, by design, an hardware memory chip or let the microcontroller emulate it ? thank you, twice. (i don't know how to say 3x in english, sorry, thrice ?) |
| ker2x:
--- Quote from: oPossum on October 07, 2019, 04:58:44 pm --- --- Quote from: ker2x on October 07, 2019, 04:50:42 pm ---Are there modern highly integrated surface mounted TTL chips ? (with dozens of gate per chips) --- End quote --- I think this is as close as you will get to that... https://www.microchip.com/ParamChartSearch/chart.aspx?branchID=30024 --- End quote --- Thank you for the quick reply. But it's a list of PLD chips, it's even worse than FPGA in my book. There is now way around it ? i have to use either very low density 74xx OR a PLD/FPGA ? Nothing in-between ? EDIT : i might be too harsh with the CPLD, there isn't anything worse than an FPGA. :box: |
| magic:
There are some more complex 74 series ICs like complete flip-flops, multiplexers, decoders. I have even seen some vintage 74-something ALU-on-chip. Wikipedia has a list of hundreds of 74 series parts, but beware that many are unobtaininum and/or have never been made in CMOS. |
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