Arish Alreja

What kind of laptop should I buy? I get this question every so often. You are possibly here because you asked me (or someone I know) this question. This page is written to provide laypersons with a framework for reasoning about computer performance, so they can systematically evaluate their options when buying a laptop. I make an effort to go beyond enumerating guidelines and try explain the underlying concepts. I believe most people can gain a deeper understanding and make good decisions based on their preferences and constraints, once they have a clear explanation of how things work. My assumption is that everyone wants a computer that is fast, reliable and versatile. Here we will unpack what each of those traits means in a platform (Mac/PC/Linux) agnostic manner.

Disclaimers:

1. I have taken and been a TA for Computer Architecture and Operating Systems courses (ECE 3055,3056) at Georgia Tech. I have a high level conceptual understanding of what makes computers go VROOM.
2. The guidelines encompass my own biases. I wrote this guide because I hate shopping and as a consequence I like things that last a long time and are high quality. I also hate clutter so I want to own as few things as possible. A laptop is a tool for me and I do care deeply about choosing ones tools well.
3. The guidelines are also limited by my own experiences. Of the 5 laptops I have used in my life, all except the first one were paid for by my place of work, so I did not have to worry about cost.
4. My background is not in I.T. and nor am I a laptop/electronics enthusiast. As a result, I do not have informed opinons about brands and models for laptops, microprocessors, GPUs, memory and hard drives.
5. Feedback and requests for clarification are welcome, but I will abstain from giving anyone advice about purchase decisions.

Without further ado, lets get started…

Part 1: What makes a computer fast? A story about drinking Orange Juice

Imagine you love drinking orange juice (OJ) so much that you always have a glass of OJ in your hand. If there were an Olympic event for drinking OJ, you would win the gold medal. You drink OJ all day every day. Maximizing your OJ consumption to superhuman levels is the sole purpose of your existence. How would you achieve this goal?

First, lets break down how OJ consumption unfolds. Your glass holds a certain amount of OJ (lets say 300 mL). When you finish a glass of OJ and need a refill. You go to the fridge and refill your glass from the container (capacity 4 L) of OJ in your fridge. A few refills later, the container of OJ in your fridge is empty. So you get into your car and go to the store to buy a new container of OJ. Maybe you buy 10 containers because your fridge is big enough. You come home, put the containers of OJ in your fridge, fill your glass from a newly opened container and continue drinking. Once the containers are finished you go to the store again. This process repeats throughout your life as an OJ drinking champion.

To maximize OJ consumption, you could do two things. First, reduce the amount of time that you are NOT DRINKING OJ. The two intervals where you are not drinking OJ are

1. Between finishing your glass of OJ and refilling it from the container in your fridge.
2. Between finishing the OJ in your fridge and returning from the store with more OJ.

Shortening these intervals reduces the time that you are NOT DRINKING OJ and increases the average rate of OJ consumption (mL/sec) in your life. Second, we can increase the rate (mL/sec) at which you drink OJ.

Hopefully, you agree with this analysis so far, even if you are wondering “what on earth does this story have to do with buying a laptop?”. Now let us map this story to laptops.

• Microprocessors/CPUs are like you
  • They process data like you drink OJ. You may think you are using Chrome or Word on your laptop, but mechanistically speaking, its CPU is simply processing data. You will feel your computer is fast if it processes data faster. Having a CPU that processes data faster is like increasing the rate of drinking OJ (mL/second) from your glass.
  • A CPU has an on-chip memory cache, which is like your glass. It holds a small amount of data, like your glass holds a small amount of OJ. It needs to be refilled periodically by fetching data from memory. Bigger caches/glasses are nicer, but only up to a point (a gigantic glass would be quite unweildy!).
• Memory/RAM is like your fridge
  • Its size dictates how much data (or OJ) it can hold
  • Faster RAM means fills the CPU cache (glass) with data (OJ) faster. This would make your computer faster (improves your average OJ consumption rate by shortening the non-drinking intervals).
• Hard Drives are like your grocery store.
  • Faster hard drives mean you will be able to fill RAM (your fridge) with data (OJ) faster. Making your computer faster/You a higher performing OJ drinker.
  • Its size dictates how much data (or OJ) is available for your CPU to process (total amount of OJ in your grocery store). For our purposes we will not worry about hard drive size (or your grocery store running out of OJ). However, in real life, you will probably want to make sure your hard drive is big enough to hold all your data.

A fast laptop is a high performance laptop. It is like maximizing your OJ consumption (mL/second) across your entire life (not just when the glass has OJ in it). The first thing that comes to mind is a faster CPU (i.e. you drinking OJ faster from your glass). The second thing that comes to mind is minimizing the amount of time your CPU is waiting for data (i.e. the intervals of time you are NOT DRINKING OJ). Let us see how different components of a laptop affect these variables and its overall performance. We will also discuss the technical specs and details you should pay attention to.

CPU (i.e. how fast you consume OJ and how big is your glass)

For the needs of a casual user, modern middle tier CPUs (e.g. Intel i5) tend to be sufficient. You can certainly make the mistake of buying a computer with a really low end CPU (clues include a very low price and/or low clock speed $<$1 GHz). If you are doing heavy computing like media encoding/editing or mathematical computation or graphics heavy gaming then you might want to look for a top tier CPU (I have an Intel i7 because I run a lot of mathematical code). An additional detail to know of is that modern CPUs can slow down/speed up their clocks depending upon load. Sometimes the specifications may describe the range (instead of the upper limit) for the clock speed.

A CPU’s specs will also usually list its on-chip cache memory size. For any you will not really be able to change its cache size (Intel/AMD figure out whats best), but you can choose to buy a more expensive CPU if you want a bigger cache. You should be aware of what cache specifications look like in the real world. There are L1 (Layer 1; closest to CPU), L2 (Layer 2; second closest to CPU) and sometimes L3 (Layer 3; even further away from CPU) caches on modern microprocessors. Their sizes are listed in most Microprocessor specifications that accompany a given laptop. If not you can look them up based on a microprocessor’s model number (which is always mentioned in laptop specs). L1 cache is usually smaller than L2. As of 2016 (when i last bought a top end laptop), caches were $<$1 GB in size. CPUs with wimpy caches might be cheaper, but their performance is usually not that great. You can get a sense about what makes for decent cache size by comparing expensive, middle tier and cheap laptops CPUs. They change with time, so I am not listing numbers to avoid misleading you with stale information.

Multicore Microprocessors and Clock Speeds: This is a bit technical, so let us begin simply. Modern microprocessors tend to be multicore. This means that your micprocessor chip may be made up of multiple CPU cores (for a quad core microprocessor, each CPU core is like 1 cylinder in a 4 cylinder engine). In general more cores are better. Sometimes a microprocessor with more cores may run at a slightly slower clock speed than one with fewer cores. This is important to know because high clock speeds mean higher power consumption which drains your laptop battery faster. Multicore microprocessors evolved for many reasons, one being the battery life of laptops. Running multiple CPUs in parallel with slower clock speeds means good performance can be achieved while drawing less power from the battery. For those who are curious why more cores do not cost more power and drain batteries faster, the technical answer is that power consumption scales exponentially with clock speed whereas adding cores increases power consumption linearly. If you remember nothing else, just remember that a cpu with more cores is better, even if the clock speed is slightly slower.

GPUs: I deliberately omit GPUs here. This page is geared towards laptops. If you are a gamer with enough money to consider a gaming laptop, you probably know more than this page intends to offer its readers.

Memory (i.e. the size of your fridge and how long it takes you to refill your glass)

When it comes to Memory/RAM, two things matter.

The first is the amount of RAM (size of fridge). At the time of writing this post, anything $<$8 GB might leave your computer running slowly if you run too many applications (netflix, chrome with youtube). It is like having a fridge that can only hold 1 container of OJ. You know you will be making a lot of trips to the store (hard drive) to refill your fridge (RAM) with OJ (data) which eventually makes its way into your glass (CPU cache). During all the time spent making those trips, you WILL NOT BE DRINKING OJ (i.e. your laptops CPU is sitting idle, waiting for data). More RAM is always better. Laptops often have open slots for you to add more RAM in the future. This allows people to buy a laptop and upgrade it later if they need/when they can afford to. Installing additional RAM is not complicated. You order RAM online, unscrew the back panel of your laptop and plug additional RAM in. If you think you may need more RAM in the future, look for laptops that have an open slow that allows additional RAM.

The speed of the RAM (in GHz) in your laptop also matters. Slow RAM is like a situation where refilling your glass with OJ from the fridge takes a long time. It will not matter how big the fridge is, you will spend a lot of time not drinking OJ because the round trip to the fridge from your living room takes a long time and your glass (CPU cache) is empty during that time. RAM speed is usually not a problem because laptop makers do not intentionally make badly designed laptops. However, there may exist laptops (on the cheaper end) out there where the design has a powerful CPU (for marketing) and poor quality RAM (for cost reduction) which then may be promoted as a powerful computer for a low price. Such computers are usually painful to use. How can you tell your RAM is fast enough? In terms of speeds, your RAM/Memory speed (in GHz) is usually slower than your CPU speed (in GHz), but it should not be too much slower. For example, my laptop is on the higher end with an Intel i7 CPU with a maximum clock speed of 2.6 GHz and I have 16 GB of RAM that is clocked at 1.867 GHz. This is about par, in terms of the difference between clock speed of CPU and RAM. If my RAM was bad, i.e, it ran 1.2 GHz, it would devastate the performance of my laptop and the amount of RAM (16 GB) would not make any difference to that outcome.

Hard drives (i.e. how long does it take to refill your fridge)

When you start a new program, like Word by opening a large word file. It is like starting with an empty fridge. You need to go to the store (hard drive) to fetch the data file (OJ) that program needs (technically, you also have to fetch the program itself from the hard drive into RAM). If that trip takes a long time, the CPU will be waiting with nothing to do (you have no OJ in your glass). There is another more nuanced function served by the hard drive. If an application like Word uses some data infrequently, the Operating System (Windows/Mac OS/Linux), may move that data out of the CPU Cache or RAM and onto the Hard Drive (into something called a pagefile). I will avoid the technical details about how and why this happens, but it does happen and when CPU tries to do something for Word which requires it to get that infrequently used data sitting in the pagefile, it will have to wait for the data to move from the hard drive to RAM and from RAM to the CPU cache. In this situation, your computer will be more responsive if it contains an SSD hard drive. The pagefile comes into play significantly if you are using a lot of the laptops RAM (70-80%)

We want fast hard drives. There are two kinds of hard drives. The first kind are mechanical hard drives, which have a motor in them. If you see the specification say 5400 or 7200 rpm, that number refers to how fast the motor of that hard drive can run. The second kind are Solid State Drives (SSDs) which do not have any mechanical parts. SSDs are faster and more expensive than mechanical hard drives. For example, a 256 GB SSD may cost as much as a 1 TB mechanical hard drive. Fundamentally, there is a quality (SSD) vs quantity (mechanical) tradeoff in choosing a laptop hard drive. I will skip all the technical explanation for how/why they are better. There are lots of flavors of solid state drives in laptops these days (some are plugged in as PCIe, PCIe NV devices and so on) and I will not try to keep up with those details on this page.

A SSD drive is essential for a laptop to be fast. Since SSDs are more expensive than mechanical hard drives, you may have to settle for a smaller hard drive or be willing to pay more for a bigger SSD drive. You will find many laptops with lots of RAM, a powerful CPU and lots of storage for low prices. But look closely and you should see that this is a marketing trick because these laptops will invariably have mechanical hard drives which are best avoided if you want a fast laptop. The moment an SSD enters the equation the amount of storage will fall and prices will rise. As an example, I have 256 GB SSD that I chose over a 1 TB mechnical hard drive. My laptop is fast but I keep a lot of data that I do not use frequently in the cloud or on external hard drives.

A hybrid approach toward hard drives in laptops is common these days, where the laptop has two hard drives. The first is a small SSD where the OS and most programs (like Word, Excel, Outlook, Chrome) are installed as well as where frequently used files can be kept so that the computer is fast. The second hard drive is a large mechanical hard drive, where you can put other files, which may be used less frequently but want to keep at hand on your laptop. You get the benefits of both SSDs (speed) and mechanical hard drives (large low cost storage). Such configurations may provide good value for money

Summary: How to pick a laptop that will be fast?

1. Microprocessor/CPU: A microprocessor which lies between moderate to high end performance. A multicore microprocessor (where more cores are better) with a clock speed upwards of 2 GHz is ideal. A bigger microprocessor cache is better as long as it fits your budget.
2. Memory/RAM: Atleast 8 GB of RAM, ideally more. If you want flexibility to add RAM later because you are unsure about whether you need to spend extra money, then consider laptops which have an open slot where additional RAM can be added later on. It is also good to verify that the RAM’s clock speed is not absurdly slow compared to your CPU’s clock speed.
3. Hard Drive: You MUST make sure you have an SSD hard drive present on the laptop, even if cost constraints force you to settle for a smaller SSD drive. Laptops with a hybrid hard drive system (a small SSD + a bigger mechanical hard drive) may sidestep the quality vs quantity tradeoff and get you both.

Part 2: Does anything beyond speed matter for a laptop? YES.

Performance/Speed may be the most important part of purchasing a laptop, but it is not the only dimension to consider. In this section, I will list a few more variables that are worth assessing when buying a laptop. This list is not exhaustive and reader suggestions to expand it are welcome.

1. Physical build: No one wants to carry a bulky laptop. Laptops are getting thinner and lighter all the time. However, some of these improvements come with the use of lighter materials which may be more prone to physical damage. Laptop hinges that connect the display to the base can break and are a particular pain point for many users. The best way to avoid build issues is to look up reviews for the laptops you are interested in. Systemic issues with the physical design and materials of a laptop model or brand are usually well reported and documented on the internet. Alternatively, you can consider how important having a thin and sleek laptop really is to you (see 3. and 4. below for food for thought) and possibly consider a sturdier laptop chassis which may not look so sleek and pretty but will be cheaper and more robust. Remember, nothing stops you from putting top notch CPUs, RAM and hard drives in a sturdier physical chassis because most laptop manufacturers allow that kind of customization when you order from their website. It may make it harder to buy a laptop from amazon or ebay though, because vendors are selling laptops on those websites are selling specific configurations that they already have in stock. As an exercise, you can compare a Thinkbad X1 Carbon with a Thinkpad T480 on lenovo’s website. The X1 is a thin sleek laptop with a good build quality (though it can still get damaged if you are rough). The Thinkpad T480 has a sturdier chassis (thicker plastic, possibly more metal) though it is slightly thicker and heavier. What happens if you go to the lenovo website and customize a Thinkpad T480 with the best CPU, RAM and Hard Drive? How does the cost compare to an X1 carbon with similar core hardware in it? Is the price difference worth the additional sleekness of an X1 Carbon to you?

2. Ports and connectivity: Having 2-3 USB ports is a nice thing to have in case you work with a wireless mouse/keyboard and want to plug in flash drives at the same time. A lot of laptops do not feature a wired ethernet port anymore (yay for WiFi penetration!) and USB to Ethernet adapters may be needed in case you need connectivity to wired network. For connecting to external displays, you want to make sure HDMI Ports are available in standard form factors (avoid funky connectors which require expensive adapters and keep costs low). My laptop (Thinkpad X1 Carbon 4th Gen) supports dual external displays and I have a HDMI and miniDP slot on it. I have no ethernet port, but 3 USB ports. I use one for a wireless mouse/keyboard, one for external drives and one for a USB to ethernet adapter because I have to connect to a server over a wired network at work. I could make do with 2 USB ports, but having 3 is really convenient. The quest to make laptops cheaper and thinner is leading to fewer ports on newer laptops. I recommend checking to make sure that number and types of ports on a laptop are enough for your needs before buying it. Do not assume that to be the case.

3. Battery Capacity: Depending upon how much you move about in your daily life, this may or may not matter to you. Bigger batteries last longer but cost more and increase the weight of a laptop. The trend toward thinner/sleeker laptops has led to smaller batteries than in sturdily build laptops. It is important to look at battery capacity (Ampere-Hours) and compare across laptops. Some sturdier laptops (like the Thinkpad T480) have slots for additional batteries that you can buy and plug in, increasing capacity beyond the basic configuration they come with.

4. Heat: Powerful CPUs running at high clock speeds produce more heat. Laptops have fans whose job is to expel this heat. Thinner laptops end up with smaller fans to keep everything sleek and conpact. As a result, laptops that are sleek and have powerful CPUs often run into heating problems because the underpowered fan is not upto the job. A hot laptop is uncomfortable to use and overheating reduces its lifespan. This is not a hypothetical, I have had a laptop with a weak fan overheat and flame out in front of me. There are two approaches I have seen taken. First, choose a slender laptop, BUT put a moderately powerful CPU like Intel i5 to minimize heating issues. Second, buy a bigger/sturdier laptop chassis (which has a bigger fan) AND put a high power CPU into it. Looking at how hot the Intel i7 in my delightfully sleek Thinkpad X1 Carbon gets, I believe moderation (in terms of powerful CPUs) is a good approach because it reduces the price tage in addition to avoiding heating issues. The finetuning involved in the second approach requires extra work in the form of reading up about cooling and fan specifications in some detail to make an informed decision.

There are many more features to consider when buying a laptop like the webcam, mic, speakers, backlit keyboards, SD cards, display resolution, touchscreen, bluetooth etc. They have not been important to me in terms of decision making because they rarely are bad in a modern laptop, so I do not have much to say about those choices. If you have input/suggestions about any of them, I would love to hear your thoughts. You can contact me using information at the bottom of this page.

I hope this page was useful to you. Thank you for reading.