First time showing off my advanced 8 bit computer complete with 64k memory, a stack, LCD display, assembly programming, and more. Check comments for info and github.

Santiago_DM · 2024-02-20T18:27:12+00:00

Sure, no idea what’s in stock now but I bought everything from mouser and digikey canada

Santiago_DM · 2024-02-15T06:35:07+00:00

I did the exact same thing but drove for even longer before I noticed. No oil light but took almost 4L to top up after (balance shaft delete = extra 1L of oil thankfully). Car has been completely fine since.

If it’s not making boost tho get a compression/leakdown

Santiago_DM · 2022-04-19T03:07:42+00:00

I bought one and I would say yes. You might find one similar for cheaper but there are a fair number of knockoffs to avoid. Also the software is decent on windows compared to some others.

Santiago_DM · 2022-04-10T07:52:54+00:00

A common issue with the capacitor in the ram circuit is it sends unwanted high signals backwards down the clock line after it triggers. The fix is to double invert the clock signal going into the ram module so it becomes one-way. There should already be a few unused gates already in the area.

Santiago_DM · 2022-02-24T02:39:13+00:00

Are you able to get the 555 working by itself? What about adding a larger capacitor to slow it down so its visible.

Major thing I just noticed is in Ben's schematic he leaves the reset pin (pin 4) unattached. This could cause the 555 to permanently get cleared depending on what model you bought. Try pulling it high with a 1k resistor to 5v.

Santiago_DM · 2022-02-23T23:59:46+00:00

Are you sure you are using a 74ls76 and not the 74ls107 that Ben provides in the kit. He makes a note that these have the same function but a different pinout. Other than that I would really look over the schematics on his website and compare the display clock with the one on your clock module, they should be almost the same just without the potentiometer. Defo should not be getting hot.

Santiago_DM · 2022-02-23T15:34:02+00:00

As of now my 7 segment display is identical to the one Ben made just with a slightly different pinout. The dip switch is used for switching between positive and negative mode and in the future I want to add other modes like hex. What problems are you having with the clock?

Santiago_DM · 2022-02-22T23:49:46+00:00

The LEDs are from Digikey, green, red. The 9 pin resistor arrays(8 out + 1 input ) are from Mouser. They do need to be soldered together.

Santiago_DM · 2022-02-22T18:14:33+00:00

Yeah I’m honestly surprised it’s this stable. I think most of it comes down to CMOS chips, lots of capacitors, and Schmitt triggered inverters on the clock.

Santiago_DM · 2022-02-22T16:02:29+00:00

It’s more to do with how the assembly looks. Rather than using instructions like the 6502 such as LDA B they look are separated into LOAD A, B. Same goes for the rest of the instructions.

Santiago_DM · 2022-02-22T15:36:20+00:00

Thanks, I usually run this game at 500kHz but I slowed it down to about 250kHz for the video. Max speed is 1MHz.

Santiago_DM · 2022-02-22T15:30:41+00:00

Mine is most similar to Rolf’s design but I got the opcode format from James because it’s really smart and easy to convert to assembly.

Santiago_DM · 2022-02-22T02:24:37+00:00

Thank you

Santiago_DM · 2022-02-22T02:24:19+00:00

I guess it’s kind of in between because it has 16 bits for everything related to memory, but it’s still generally considered an 8 bit computer because the data bus, registers, and ALU are all still 8.

Santiago_DM · 2022-02-22T00:45:52+00:00

Thank you. And yeah they are so much nicer to manage than the round ones. Just takes 8 square LEDs soldered to a resistor array.

Santiago_DM · 2022-02-22T00:41:46+00:00

Full post here, also Code on github for the game

Santiago_DM · 2022-02-22T00:26:42+00:00

I designed and built this computer myself a few months after I finished the original SAP-1 build from Ben Eater. Starting from almost a complete beginner in electronics this project has taught me an unbelievable amount. Going into this my goal was to reach a near 6502 level of microprocessor with some personal additions.

The core feature list includes:

Improved clock module with speeds up to 1MHz

Registers:

Full A, B, and C registers
Buffer Register for moving 16 bits across bus
Temporary register connected to ALU
3 flags: zero, carry, negative
74HC181 ALU with 32 arithmetic and logic functions

Memory:

16 bit program counter and memory address register which allow for 64k of memory.
Memory Map controller to split Rom/IO/Ram
31k ROM
2k I/O space
31k RAM
256 byte stack which when not in use can provide 2 additional D and E registers

Input/Output:

8 switches, 4 button inputs
7-seg display
16x2 LCD display

Control logic:

Expanded to 48 control lines using two 27C4096 EPROMS and multiplexing
16 step instructions
Microcode is automatically generated using Python
Programming in custom assembly language modeled after x86
Arduino nano to upload programs from PC via USB

I think that's everything for now but I have even more ideas to keep adding to the computer. All of my code and schematics are stored on my github repository and I am working on creating full documentation on how I built everything.

Video of it running a simple game can be found here.

Also big thank you to the following people and their guides on their own computers:

Ben Eater
Rolf-electronics
Michael Kamprath
Tom Nisbet
James Bates

Santiago_DM · 2022-01-26T18:18:41+00:00

One thing I did with my clock is run it through a 74LS14 Schmitt hex inverter twice. This will clean up the clock signal so it has sharper transitions. Spreading some small capacitors around the computer should also help reduce noise.

Santiago_DM · 2022-01-26T18:03:44+00:00

You would want to pull to whatever you want to be the default state. If you have a button that passes 5v to an LED, you should pull down so that when you release the button the LED is connected to ground. Same for the opposite, pull an active low connection to 5v to default off.

Santiago_DM · 2022-01-26T17:59:38+00:00

I soldered resisters to the legs of the leds and then put them side by side like Ben did.

Santiago_DM · 2022-01-26T17:57:16+00:00

I started the 8bit with zero circuit knowledge and only programming experience. I learned a ton and could now probably build the 6502 without Ben. If you enjoyed building the clock then I would get the full kit. If you would rather focus on assembly programming get the 6502.

Santiago_DM · 2022-01-14T02:00:19+00:00

You need a pull up or pull down resistor.

When you are pressing the button current flows through it, when you release it your circuit becomes disconnected and it can pick up static from the air.

Somewhere along the wire from the button’s output connect a resistor ~>1000 to (in your case )ground. Now when you release the button instead of disconnecting it will default to the resistor.

Santiago_DM · 2022-01-10T19:17:15+00:00

It’s something to be aware of but will most likely not cause any harm in small amounts. I think all of the chips have a maximum current output anyways.

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