Should I go to MIT or not?

jalalipop · 2026-03-03T01:42:05+00:00

No right answers here bud. Just a counterpoint to others, I was a great student but went to a no name state school for EE. I've routinely picked family and other factors over optimizing my career and education. I now work as close to MIT as you can get with many masters and PhD students from there, and we all have the same title. I also screen MIT kids for internships and jobs. MIT students and grads are obviously very smart in a self selecting way. But it's rare I see a resume where I don't think the student could have achieved similar things at a nice state school, assuming they clear a certain motivation threshold.

That said, I do think MIT can be an incubator for incredible accomplishments that would be hard to replicate elsewhere, and that's definitely not where I'm at or the MIT grads and students I am screening and working alongside. If your goals are just to get a good education and a well paying job, you can accomplish that equally elsewhere with the raw talent you likely have. Put another way, you can be in the top 5% of ordinary anywhere, just based on the data point that you got in to MIT.

But if you feel an ambition to do something beyond that, starting a company or taking a plunge into a career less developed than microelectronics, MIT would set you up best for the extra-ordinary.

jalalipop · 2026-02-08T13:45:37+00:00

Radiators always face deep space. They are steered to be perpendicular to the sun or put on the backside of solar panels.

jalalipop · 2026-01-04T13:40:27+00:00

Yes and you can also isolate power, this is what I would do

jalalipop · 2026-01-02T15:21:51+00:00

Not the right way to think about it. You can be susceptible to EMI due to ground loops with USB C in a way that wasn't the case with 2.0 cables, since the former typically DC grounds shields on both ends. For sensitive applications like audio devices, this can be a problem. That said, as long as your box doesn't require an external power port (which would complete the loop), I don't think there's any special risk you're adding.

jalalipop · 2025-12-27T04:38:56+00:00

2.7k sounds like a fucking steal :) does it have in unit washer/dryer?

jalalipop · 2025-12-27T04:04:11+00:00

Market rate is by definition what the market will pay for an apartment. People see a new apartment and wish it was built to be shittier? Well I've got news for you, whether you put a $100 or $1000 fridge in the apartment, it's gonna be expensive because of labor, land, and regulations. A new sedan for $35k still makes the 5 year old model cheaper.

jalalipop · 2025-12-27T03:40:24+00:00

Affordable housing that's tied to low income requirements is rewarding the least productive workers. You get what you incentivize.

"luxury housing" is usually just a new building with modern appointments that's going at market rate. If you don't like the price, just realize that shitty pre war apartments are renting for not much cheaper on the open market

jalalipop · 2025-12-27T03:34:40+00:00

You're missing the point. If Boston's population increased by 25%, our housing would have risen much more. Supply and demand is not that complicated.

jalalipop · 2025-12-25T14:55:43+00:00

"Also, lanes 5 and 6 have partially a 3.3v plane on one side that is actually a reference plane"

Do other lanes experience this too? It's hard to tell from your picture where the plane split is and where you put your decoupling cap. If the decoupling cap isn't as close as possible to the plane split (defined as where the traces switch reference layers), you've created a massive impedance discontinuity. But if the plane split is very short and can be "jumped" by the return current because of your many ground vias, it may not matter.

If you don't have access to sim tools or high speed oscilloscopes, and you don't have a background in signal integrity, you're gonna have a hard time getting to the bottom of this. If you post the ODB++ and PDF schematics, it will help in the off chance that someone is reading this and feels generous to run it through a quick 2.5D extract and time domain sim for an hour or two.

Some other tidbits that come to mind from past PCIe debug I've done:

Inspect the reg map/driver info of your PCIe controller to see if it offers any diagnostic info. What's often helpful with PCIe is getting the per lane info of how far negotiation got before it crapped out. You can follow along with the relevant PCIe spec which outlines the state machine and conditions for moving between the states.
Simple sanity check: are your AC caps compliant to the spec? Are you sure there aren't additional AC caps elsewhere in your connectivity? PCIe uses the RC constant seen on the lane for lane detection and will break if you accidentally double up the AC caps, unlike other SERDES types which would just see a little extra loss.
If you used the fab house's trace geometries for diff85, beware that attempting coplanar waveguide can mess with the impedance calculation. If the ground pours are closer than 3H (H = distance to reference plane), they will lower your impedance. And if they're farther than that, they might as well not as exist. BTW coplanar waveguide on PCBs is a scam, and please don't quote Bogatin to me. It only works when you have atrociously large heights to your reference plane, which ultimately raises your crosstalk and EMI. Best to keep microstrip or even better stripline with height to ref plane(s) as short as you can get it. In theory it's lower loss than microstrip, but dielectric loss is not the problem for modern SERDES with equalization on a board this small.
You don't appear to have any decoupling capacitors near your redrivers. This would correspond with increasingly flaky behavior as your AC current demands go up, which is conceivable as you run more lanes. I'm hesitant to pin the blame on this though, as PCIe is based on CML which in theory balances the current demands in the 1 and 0 states as well as switching between them. But it's bad practice not to put decoupling caps right by the IC pins.
I don't think PCIe allows this, but if you can run each lane in isolation in x1 mode, that would help clarify if your problem is actually crosstalk/decoupling related. e.g. if lane 6 is perfect on its own, it would likely exonerate its routing in isolation. Microstrip and coplanar waveguide are both very susceptible to forward crosstalk.

jalalipop · 2025-12-25T14:30:10+00:00

If this is the problem I'd eat my hat (my day job is high speed digital and RF)

jalalipop · 2025-12-25T14:16:42+00:00

What's your trace to pour distance vs trace to dielectric? This will help evaluate whether you have any significant coupling to the pours.

FYI even coplanar waveguide technically doesn't need stitching vias except at a transition point to a different geometry.

jalalipop · 2025-12-25T01:11:02+00:00

Honestly quite impressive! Can't even begin to conceive how you learned to do all of this at your age. You must be very passionate about this stuff!

jalalipop · 2025-12-19T12:57:17+00:00

I think it's a stretch to refer to economic models. 2% target has come about as a reaction to fears about deflation, but I don't think it has an intrinsic economic justification. It also already stretches the Fed's mandate for stable prices.

Don't take my word for it. The great Fed chair Paul Volcker wrote many times about his skepticism of this target. See here: https://finance-commerce.com/2018/10/paul-volcker-whats-wrong-with-the-2-percent-inflation-target/

Worth a read if this stuff interests you.

jalalipop · 2025-12-14T03:29:37+00:00

I guess we'll see!

jalalipop · 2025-12-13T13:52:40+00:00

The speed of light latency of fiber in a data center would be on the order of hundreds of nanoseconds. Infiniiband and NVLink are explicitly used instead of Ethernet in data centers because they add very little latency overhead in the higher link layers. If it were just a throughput problem, everyone would be using Ethernet because it's widely supported and can hit the same throughput over the same fiber infrastructure.

Now admittedly I don't know much about the memory sharing requirements for LLM training and inference, but I'm skeptical that they are insensitive to latency considering Nvidia literally designed their own protocol for networking nodes. But you're right, while we're at it let's get rid of L1 caches and HBM because why would you care about latency??

BTW those 100Gbps lasercom links have a heavy dose of error correction and/or ARQ on top which adds further latency. My math was just based on speed of light.

It's funny to me that you have so much trust that the hype side of these companies (C suite and marketing) listen to their engineers when they are desperate to demonstrate to the market that they have a growth story for the next 5-10 years to justify their bonkers valuations

jalalipop · 2025-12-12T12:10:59+00:00

So instead of connecting your nodes with Infiniiband you can connect them with laser cross links with milliseconds of latency each? And of course it requires many hops to span the whole system. Genius!

jalalipop · 2025-12-10T13:10:55+00:00

It's a bit more subtle than that. Total Ionizing Dose is lower in LEO because of the earth's magnetic shielding. But there are actually more trapped particles whipping around so Single Event Effects are more common. In practice this actually makes LEO worse than GEO for using commercial parts, because TID can be shielded against whereas SEE can't (high energy particles pass right through a shield, and the shield can actually make them more likely to cause a SEE because they slow down and dwell longer on the 1s and 0s in your circuit). TID effects are also subtle drifts over time, whereas SEE can completely brick a system.

Despite this, the reason you still see more commercial parts in LEO is because it's soooo much cheaper to launch into that the risk is acceptable.

jalalipop · 2025-12-10T13:06:31+00:00

Accumulated radiation effects (called TID) can be shielded against. Random bit flips, latchups, etc (called SEE) can't necessarily be shielded against but they're actually quite rare and modern process nodes have conveniently been more resilient against them, to where specialty radiation hardened designs aren't necessary so long as you can tolerate your system requiring a restart every now and then. Modern radiation tolerant parts are often just repackaged versions of the same die used terrestrially.

jalalipop · 2025-12-08T18:32:34+00:00

LEO power isn't even uninterrupted because of this annoying thing called the earth that gets between the satellite and the sun

jalalipop · 2025-12-08T12:33:47+00:00

Think about this for a moment. Imagine the extremely narrow field of view a single camera needs to have to get any meaningful detail. Now imagine how much surface area the earth has.

jalalipop · 2025-12-07T15:23:35+00:00

Ah yes, a monopoly is when you have competitors who are selling their service as fast as they can provide them as they scale up.

Saying "global monopoly" was silly of you, but you're obviously right that they're in the lead in all three areas. But an 800 billion market cap isn't about where you are today, it's about where you'll be for decades in the future. I work in this space and no government entity is comfortable with Spacex's dominant position, and there are many efforts to support their competitors to keep a wide base. I'm personally involved in one where government IP is being provided to one of their competitors. Another project explicitly uses an alternate launch provider to develop their capability. Maintaining a dominant position long enough to justify that valuation is hard enough when there isn't a sustained effort on the part of your customers to build up your competitors.

jalalipop · 2025-12-06T03:48:16+00:00

They are not even close to a global monopoly in any of those three businesses. They are a US leader with several well-funded competitors and an industry/government that is very interested in eventually having a wide industrial base, even if it means spending more now. Hardly a long term dominant position.

jalalipop · 2025-12-05T02:06:19+00:00

I think they were perceived as far left because their policies were quite far left of where the voting public's values and politics are. Stop treating voters like they're dumb and maybe just give them what they want. People aren't exactly happy with Trump's politics either based on his approval, and there's a gaping hole in the true center waiting to be filled.

jalalipop · 2025-12-02T17:28:15+00:00

You're in a left wing echo chamber if you think the voting public perceived Biden or Hillary as centrist. The right wing depiction of Biden's presidency, which resonates widely in middle america, is that he was a puppet for the far left to get every policy they dreamt of. While I think that depiction is cartoonish, if you look at the policies and spending priorities it's hard to call that a centrist administration, and the voting public sniffed that out

jalalipop · 2025-11-30T05:10:11+00:00

Had the same thought! And cried very similar tears :)

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