sparky

Joined 17 years ago

Karma
1,209
Submissions
395
Member since
Apr 23
grad student in computer architecture -- i like to dabble in a lot of things though

I can be reached at johnso(85+2)@illinois.edu, where the parenthesized expression is replaced with its result.

http://blog.mattj.me

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Recent submissions

Comment · 9 years ago
If you're earning $300k/year in California, you're paying ~$22k in state income tax, so you should be itemizing on your federal return with or without the mortgage, and subtracting the standard deduction from the benefit doesn't seem right.
Comment · 12 years ago
Comment · 12 years ago
Cheapest possible toaster oven + cheap multimeter thermocouple for manual temperature control + {paste flux, solder paste+stencil} works better than you'd think for soldering BGAs. Even honest-to-goodness reflow ovens can be had on eBay for $300-$400 (search "T962"), which would give you another one or two nines of reliability by circulating the air and having more precise temperature control.

Schmartboard also makes 1.0mm pitch BGA adapter boards, but a lot of the high-end stuff these days is moving to 0.8/0.5/0.4mm pitch. Of course, for those kinds of things, the extra parasitics of an adapter board are probably a no-no in any case.

Comment · 12 years ago
Comment · 12 years ago
Yeah, I think that comment conflates three things: 1) The regulatory burden of going public (Sarbanes-Oxley compliance et al.) pushes companies to stay private, which keeps the average Jane from investing in those companies via the public markets.

2) For those companies that are privately held (whether that's because of the regulations in #1 or for more fundamental reasons), separate regulations (accredited investor rules et al.) prevent the average Joe from investing privately.

3) On top of #1 and #2, market forces and norms give more investment opportunities (both public and private) to large, established players than individual laymen. For example:

* Companies may prefer to take $1M each from 5 large investors than $1k each from 5000 people, both to reduce logistical burden and because those large investors statistically have other unique things to offer like expertise, advice, and connections. This is unfortunate for the small-time-but-sophisticated investor, but seems quite rational.

* IPO shares only being offered to large friends and clients of the underwriter. The justification is reduced logistical overhead as in the previous case, but the true motivation is widely suspected to be cronyism.

Comment · 12 years ago
Propagation velocity in copper is within a factor of 2 or so of c; you would have to length-match even at vp=c, given a short enough clock period.
Comment · 12 years ago
Isn't that for a 1000x ROI? 1000%=10x, so even selling 1% on Kickstarter at a 200M valuation would yield something like that.
Comment · 12 years ago
I think he means you get an 80k refresher every year that vests over 4 years (20k/year). After 4 years, you have a full pipeline and 4 tranches (80k/year total) vest every year.
Comment · 12 years ago
Aliasing conflict!

This is about doing histogramming on an FPGA, not a tool to group FPGA dice into speed grades :)

Would be interesting to see how an FPGA stacks up against a GPU on this problem. GPUs are very fast at parallel histogramming, but hardwiring the number-to-bin-index computation for a particular problem instance might buy you quite a bit of energy efficiency, or even possibly a bit of performance if the computation involves a divide. If the bins are of non-uniform size and the indexing computation involves a binary search on a lookup table, it seems like the much higher clock speeds on a GPU would win out.

Comment · 12 years ago
The lack of palletization on Target's trucks seems inefficient at the store level, but may be justifiable at the company level, since Target owns its own distribution centers:

* Trailers are 9-10 feet high, so a fully palletized truck would (a) Have very tall unwieldy pallets, and you'd have to carefully order things so boxes on the bottom don't get crushed, (b) need racks or something similar to hold multiple tiers of normal-height pallets, or (c) be half-empty

* Even with the current process, getting boxes off the truck is not even close to the bottleneck. When I worked at Target, 2 people threw boxes onto rollers, 5-6 people sorted the boxes onto pallets organized by area of the store as they went by, 2 people rolled those pallets onto the sales floor and threw each box in front of the appropriate aisle, and ~20 people opened the boxes and stocked the shelves. The 2 people unloading the truck could always keep well ahead of the 20 on the sales floor.

* An alternate strategy might be to sort the boxes into pallets by store area at the distribution center rather than at the store. You might get some economies of scale out of doing this process for 100 stores at 1 distribution center, but it may still not be worth it to put all that needed floor space, latency, and congestion in what I imagine is already a very congested point in the supply chain. Better to distribute that part to the endpoints, since you already have 100k square feet per store to work with that's just sitting there while the store's closed.

Comment · 12 years ago
LLVM has an open-source PTX backend, and newer versions of the official CUDA compiler use LLVM to generate PTX internally, but PTX is a device-independent intermediate layer, and the PTX-to-SASS compiler is closed-source.
Comment · 12 years ago
Comment · 12 years ago
The "stereo" part likely adds significant work (up to 2x), since you're rendering from two points of view.
Comment · 12 years ago
fifty times as much storage.

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