mxenabled / mxcpu

Arecibo / MXCPU Billboard Puzzle

MXCPU

Arecibo / MXCPU Billboard Puzzle

MXCPU Instruction Set

Note: The results of all operations are modulo 256 and all memory slot addresses are modulo 16.

Op-code	Operand 1	Operand 2	Explanation
B1	byte #	--	Set PC to byte #
B2	Memory slot [00-0F]	byte #	If accumulator equals register, jump to byte, otherwise, advance program counter 3 bytes (to next instruction)
B3	Value	byte #	If accumulator equals value, jump to byte, otherwise, advance program counter 3 bytes (to next instruction)
C0	Memory slot [00-0F]	--	Add memory slot value to accumulator
C1	Value to add to accumulator	--	Add value to accumulator
C2	--	--	Increment the counter
C3	--	--	Decrement the counter
C4	--	--	Reset the counter to zero
C5	--	--	Copy counter to accumulator
C6	--	--	Copy accumulator to counter
D0	Memory slot [00-0F]	--	Copy memory slot value to accumulator
D1	Value	--	Set accumulator to value
D2	Memory slot [00-0F]	--	Store accumulator in memory slot
00	--	--	Halt program execution

Run

Download a stand-alone JavaScript interpreter such as rhino.

Write your program into a file. For example, to sum the numbers from 1 to 10 and store the result in memory slot 0x00:

C4 D1 00 D2 00 C2 C5 B3 0B 10 C0 00 D2 00 B1 05 00

Run your program: $ rhino mxcpu.js myprogram.txt

Running program
Terminating
PC			0x10
INC			0xb
ACC			0xb
MEMORY			0x37,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0

mxcpu's Issues

ReferenceError: readFile is not defined

Encountered "ReferenceError: readFile is not defined" when trying to run the emulator using Node.js (I had some trouble installing rhino).

Note: When mapping out the sample problem (sum of 1-10), I couldn't figure out why the sample output in the README.md shows a value for memory slots 0x0E and 0x0F (0x3 and 0x8, respectively). Maybe these values carried over unintentionally from the first exercise?

Cool stuff! :)

Loose interpretation of memory addresses in instructions

I noticed in the emulator code that the higher nibble of a memory address is dropped. For example, D0 00 behaves the same as D0 D0. Can I use this to my advantage?

mxcpu.js misses formatting error if it is deep in the program

I referenced 0F in one part of some code I was messing around with, but I accidentally put the letter O instead of zero. While both the tests on mx.com/cpu as well as when running through Rhino locally caught other issues similar to this, it missed this issue for some reason. When running locally, it succeeded, and then when running against tests online, the program goes into an infinite loop, blocks the UI, and eventually crashes the page.

I don't want to post the actual code here, since it's pretty close to a working solution, but it was when I used the B2 op code. Also, when using the B2 op code earlier in the code with the same format issue, it breaks as expected and throws an error on Rhino and shows a message on the webpage that I need to match the requested format. It's only later, with the B2 op that's in a for loop that it swallows the error or goes into an infinite loop.

Feel free to reach out to me personally if you want the full code for reference. I submitted a working solution, so you should have my contact info. I'm probably the only person so far who has the initials JJ, and I submitted this morning, so it should be pretty easy to track me down :).

Completing the challenge results in SPAM

Steps to Reproduce

1. Successfully complete the coding challenge.
2. Provide your email address

Expected
One or several of the following:

• Email acknowledging completion of coding challenge.
• Email containing recruiting information.
• Email following up on submitted solutions.
• No email.

Actual
MX propaganda emails to the tune of:

• MX THE MOBILE REVOLUTION IN BANKING: FROM CHINA TO THE US
• The state of aggregation & open banking: why it matters for you and your customers
• MX ONLINE AND MOBILE BANKING FOR EVERYONE
• MX 50+ YEARS OF EVOLUTION IN THE FINANCIAL INDUSTRY
  ... and many more!

ReferenceError: CRC32 is not defined

JavaScript error: "ReferenceError: CRC32 is not defined" when trying to "Run Tests!"
Is this part of the quest?

Safe to assume initial 0 values?

Is it safe to assume that the accumulator, counter, and all memory addresses are initialized to 0? This seems to be the case in the emulator but I don't see anything about it in the specs.

Submission error

I finished the challenge and verified my answers. However, when I go to submit my answers and information it fails to submit and just sits on the page.