Mengenal arsitektur MIPS: single-cycle vs pipelining

Arsitektur komputer merupakan hal yang menarik untuk dipelajari. Dengan memahami cara kerja komputer, khususnya processor, kita akan lebih mudah belajar IT, khususnya pemrograman dan komputasi. Masalahnya processor era modern menggunakan sistem yang kompleks, contohnya seperti i9, i7, m3 maupun processor buatan AMD dan IBM. Untuk mempelajari cara kerja processor, kita bisa memakai MIPS (Microprocessor without Interlocked Pipelined Stages), processor jaman baheula yang sudah tidak diproduksi di zaman ini [2]; namun konsepnya tetap digunakan oleh processor modern yang sekarang kita gunakan.

Secara umum, cara kerja processor dilihat dari data pathnya dapat dibagi menjadi dua yakni single-cycle dan pipelining.

Gb 1. Simple data path pada arsitektur MISP

Berdasarkan gambar diatas, bisa dijelaskan tahapan datapath pada eksekusi single-cycle sebagai berikut:

1. PC (program counter): menahan alamat dari instruksi yang akan dieksekusi.
2. Add: Menambahkan nilai dari PC(alamat saat ini) dengan nilai konstan 4, dan menghasilkan alamat tentatif untuk instruksi selanjutnya. (jika instruksi selanjutnya adalah percabangan dan syaratnya terpenuhi, maka alamat tersebut tidak dipakai).
3. Add/ALU result: bagian ini menghitung alamat target selanjutnya (branch target address). Inputnya adalah PC+4 dan output dari konstan 16 bit yang di-sign extend menjadi 32 bit dan digeser kiri (left shifted) 2 bits.
4. Mux: bagian ini menghasilkan alamat selanjutnya. Jika instruksi selanjutnya adalah conditional branch, maka output dari 3 dipilih, selainnya digunakan outout dari 2.
5. Sign-extend: bagian ini meng-extend/memperluas input 16 bits menjadi 32 bit (dengan menambahkan 16 bit baru dengan "tanda" yang sama dengan bit paling kanan).
6. Mux: memilih data yang akan ditulis pada register tujuan dari data yang dibaca dari memory dan data hasil perhitungan ALU.

Meskipun cara kerja processor single cycle diatas dapat bekerja dengan baik namun tidak dipakai di komputer modern karena:

• Semua instruksi harus dieksekusi dalam satu siklus.
• Lama waktu eksekusi merupakan jumlahan dari tiap instruksi, artinya jika ada instruksi yang dieksekusi cukup lama, maka instruksi lain akan menunggu,

Sebagai solusinya, diperkenalkan pipelining. Analogi yang cukup sederhana adalah proses mencuci, mengeringkan, menyetrika dan melipat/memasukkan lemari. Pada teknik single-cycle (satu siklus), semua tahapan dilakukan berurutan, mencuci dulu, setelah selesai baru dikeringkan, kemudian disetrika dan dimasukkan lemari, baru mencuci lagi. Pada teknik pipelining, sambil mengeringkan, kita bisa mencuci lagi, saat cucian pertama disetrika, cucian kedua dikeringkan, dan cucian baru (ketiga) bisa mulai dicuci. Dengan cara pipelining seperti ini, waktu pemrosesan menjadi jauh lebih sedikit. Gambarnya ditunjukkan seperti di bawah.

How to obtain CoE from Kanazawa Immigration Buerau (Nagoya Branch) and send to your country

Here is a small note I made when applying for Certificate of Elibility in Kanazawa Immigration office (branch of Nagoya Immigration office).

List of document (as described by Immigration office web site):

1. Application Form for Certificate of Eligibility (available on the Immigration Bureau website).
2. Proof of applicant’s relationship with the student. One of the following documents indicating the relation under the student’s country’s laws: A copy of an applicant’s family register, marriage certificate for spouse, and/ or birth certificate for children.
3. A copy of the student’s Residence Card or a copy of his/her passport
4. Proof that the student will be able to support his/her family throughout their stay in Japan. 
1. Privately financed students should submit their bank statement indicating balance of deposit or a duplicate copy of remittance from home country. 
2. Japanese Government (Monbukagakusho) scholarship students should submit Certificate of Monbukagakusho Scholarship Student.
5. Certificate of Studentship issued.
6. 1 photo (4cm×3cm) of each family member taken within 3 months of the day of application
7. A self-addressed envelope affixed with a 392-yen stamp (for the recorded delivery purpose)

Note: In some cases, additional documents will be requested by the Immigration Bureau.

List document I submitted

University Entrance Speech by Asano-san: Lessons Learned

Today, I got one of the best speech I ever heard directly in university entrance ceremony (入学式). It was delivered by the president of my university, Asano-san. Moreover, the president is known in our university by his "Asano vision",  a vision that he brings to "rule" this university.

First things that I caught from his speech is about the feeling of new student entrancing the university. When entering graduate university, there is two type of students: 1) one who wants to take the challenge, 2) another who worries whether he/she can graduate from the university. No matter which type you are, you should do your best to tackle obstacles in the university. Attend all class, never miss one, submit all homework, focus on your research, make it narrow as much as possible, and you will be graduated.

To support this idea, Prof. Asano shortly described the work of Angela Duckworth of University Pennsylvania. It is not diligent or IQ that makes success in life but GRIT: perseverance and passion for long-term goals. An ability to keep hard work. The rule is called 10000 hours rule. The rule implies that 10000 hours of continues effort is the key to success. However, making effort without aims didn't make any significant result. Set the final aim, and divide it into pieces, everyday goal. Reach goal one by one. Grit nonetheless demonstrated the incremental predictive validity of success measures over and beyond IQ and conscientiousness. Collectively, these findings [1] suggest that the achievement of difficult goals entails not only talent but also the sustained and focused application of talent over time. Our head (read: brain) has the same capability as Einstein's brain. It depends on us to use it or not to use it. The problem is a will, there is or not, not the capability (can or can't).

The second one is about constant work, be persistent. Asano-san does running for 6 km every week on the treadmill. No matter how busy he is, as long as he can run, he will run. No ambition, no target. He just wants to keep persistent although he will get old and older. He also keeps walking around campus every Thursday, after lunch. The other record is he keeps his weight, every day. Another JAIST professor walks about four kilometers every day after completing the class/lab. He takes the route from the university to the nearest station. For your information, there is a free shuttle bus from university to the station. So, money is not the reason.

The last one is about the self-confident. It is the most important thing in a life. If you have self-confident, how big the task is given to you, you can accomplish it. To maintain a strong will, we need physical strength by physical exercise. Of course, you need to develop your skill. In contrast, although you are a skilled student, if you are not self-confident, you will be in trouble.


Additional reference:

1.  Duckworth, Angela L., Christopher Peterson, Michael D. Matthews, and Dennis R. Kelly. "Grit: perseverance and passion for long-term goals." Journal of personality and social psychology 92, no. 6 (2007): 1087.

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About this text

I analyzed the text above by using coh-metrix and I got the following result.

Kembali ke Jepang: Life at Nomi

Tak terasa, sudah tiga tahun saya meninggalkan Jepang, tepatnya 3 tahun 3 bulan. Alhamdulillah, Allah menakdirkan saya kembali ke Jepang melalui MEXT. Melalui seorang teman, saya mendapat informasi tentang beasiswa MEXT, kemudian saya apply beasiswa tsb, wawancara dan alhamdulillah diterima. Saat bekerja di Jepang dulu, saya sudah beberapa kali apply beasiswa dan gagal. Saya sendiri bisa ke Jepang saat itu dengan beasiswa Jasso, kemudian bekerja di sebuah perusahaan Jepang di Mie-ken. Pelajaran yang bisa diambil, jangan takut untuk mencoba. Puluhan kali saya mencoba mendaftar beasiswa (Jepang) sejak S1, kemudian setelah lulus S2, kemudian setelah jadi PNS, akhirnya berbuah. Sebelumnya saya diinstruksikan untuk mendaftar beasiswa ke Eropa, namun hati kecil saya ingin kembali je Jepang, lingkungan dimana saya sudah terbiasa. Dan Tuhanpun mengabulkannya, Aamiin.

Saya masih ingat betul email terakhir dari calon supervisor yang mereject aplikasi saya, beliau menulis: "I regret to tell you this bad news, but I am hoping your fruitful stay in Japan", dan alhamdulillah, insyaAllah menjadi kenyataan.