RAM module build - part 1

Part 1 of building the RAM module for the 8-bit computer.

Complete parts list (everything in the RAM module):
- 2x 74LS189 (64-bit random access memory)
- 2x 74LS04 (Hex inverter)
- 1x 74LS173 (4-bit D-type register)
- 4x 74LS157 (Quad 2-to-1 line data selector)
- 1x 74LS245 (Octal bus transceiver)
- 1x 74LS00 (Quad NAND gate)
- 14x LEDs (9 red, 4 yellow, 1 green)
- 3x 1KΩ resistors
- 1x 0.01µF capacitor
- 22 gauge wire
- 5 volt power source (e.g., a USB phone charger)

[nrt]

You're like the Bob Ross of computer engineering: informational, soothing, and encouraging.

[mcgallionjr]

Finally, a video that deals with something other than the Arduino. Thank you.

[iliapopovich]

I notice that his lessons run interrupted not like most of the others where the video suddenly jumps. It's a real time experience and if something goes wrong you can see it. This man is a real professional .

[christatler]

This thing brings memories. Sometime in the 70’s when I was a child, a parent of one of the children at school had built a pong game that connected to a TV. It was built into a frame that contained dozens of PCB’s that I can only assume contained 74 series logic. There were hundreds of LEDs in rows displaying all the data and address lines, control lines etc, and of course I didn’t know all this stuff then, it looked impressive and played a huge role in my interest in electronics for life.

[larrybud]

The amount of planning which went into each board is incredible. Leaving space at 4:42 to bring the output of the 4th pin so that the LEDs are lined up did not go unnoticed.

[nilupulperera]

Dear Ben, What a nice video series. This is what I was looking for. I do not have any engineering background. I have a medical background. Your explanations are so simple to understand everything effortless. You are a great teacher. Thank you very much. Please upload more videos in this topic.

[garydunken]

Your breadboard layout and interconnections are so neat. Well done.

[kei_otake]

I've been following everything up to this point, but it's still mind-blowing to see that the binary numbers are actually stored in each address that they're written to. The additive powers of technology are amazing!

[JerryEricsson]

Keeps striking me as I watch these wonderful videos, with all those great multi color LED's showing us what is going on, put them all in a frame, install a translucent panel over them, place them on a counsel with a couple of silver chairs, and we have the computer on the Jupiter II!

[jacobdykstra]

I got the book you showed in the first video and have been building this inside an FPGA. Been following along and your videos compliment the book well. Its coming along great so far. This project is a great way to learn system architectures. Thanks a lot for this series!

[KiwiSoupVR]

I've just found you a couple days ago but you've already compelled me to buy a bunch of this stuff

[gnudarve]

If you invert the data bits on the way into the RAM you would not need the tri-state buffer chip since then you could use the RAM's tri-state outputs to get it on the bus and reduce the chip count by one.

[remsalt]

hi ben! iv been following this 8 bit computer playlist for a while now, i dont have the parts to actually build it so iv been using minecraft with logic gates. i had to build all the chips myself. still very fun.

[bryan]

seeing it work in the end gave me heart eyes because of how easy you made it look and how it functioned manually and perfectly

[jombx]

I’ll remember this when RAM prices go back up

[nonamex]

This guy is smart in a beautiful way. The way he dose and explains things its like art

[dingodog]

I had to use an 8 bit register instead of 2x 4 bit ones. After a couple of goes working out the right type I got it working. 👍 amazed myself and actually understood what I was doing. Great work Ben.

[gustavopereira]

Man, your videos has been amazing for me to learn english and digital eletronic. thanks a lot!

[blazaniterules]

What is really nice about this setup with the two 74ls189 chips is that it is easy to expand. What i mean by this is that you can simply double up this setup by building another RAM module exactly the same as before, and use it as another bit worth of addresses. The way that you would do this is by connecting the fifth bit of the addresses dip switch to the second RAM module's enable lines through an inverter, so that when you want to store more stuff, you can switch between which module you are storing in. The only annoying thing is that you would need to connect all the address lines of the first module to the second module which is a little inconvenient.

[cortstar]

you're like the Bob Ross of electronics