What are the determining factors responsible for why Intel chips can clock at 4Ghz or higher speeds, while other processors such as ARM can't? Is it because Intel's state of the art fabs or is it the architecture of the x86? It hard to understand how a complex chip like the i7 can clock so high.
Electronic – What makes intel capable of very high clock rates
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The problem with using a microcontroller to drive an LCD is that an LCD requires constant attention. This can be mitigated with a CPLD driven over SPI (using DMA, of course), but then you run into the other problem: Color LCDs require a lot of data. 320x240 in black and white is marginal at 9.6KB, but make it 24 bit color and suddenly you need to deliver 230KB of data in 1/60th of a second. (Don't forget, though, that you can get 4-bit, 16-color control just by tieing the low 20 bits to one setting). A 24-bit frame buffer no longer fits in onboard RAM on most microcontrollers, and you probably don't have time to read from an external RAM chip, clock the data out, and still do other processing. Trying to do this with a CPLD (or an FPGA) and a RAM chip gets you well over the $2 price that caused you to balk in your question.
The traditional solution to interfacing a microcontroller with a color LCD is a display controller like an SSD1963. Here's a very simple block diagram:
Parallel input to a big RAM frame buffer (Translation: More than $2) interfaced with a register-configurable parallel LCD interface. The parallel input is usually compatible with a memory bus interface.
The color LCD market is not always easy to find on the web, usually being the domain of OEMs only, with the rest buying displays from companies who integrate the controller with the display. The best resource I've found has been Crystal Fontz, specifically this page on choosing graphic LCDs. Scroll to the bottom for the controllers, which include the following options (note: Not all are color controllers):
- Epson S1D13521B01 E Ink Broadsheet (1 module)
- Epson S1D13700 (11 modules)
- Epson SED1520 Compatible (8 modules)
- Himax HX8345 Compatible (1 module)
- ILITek ILI9325 Compatible (3 modules)
- KS0107/KS0108 Compatible (26 modules)
- Novatek NT7534 (14 modules)
- Orise Technology OTM2201A (1 module)
- Orise Technology SPFD5420A (1 module)
- RAiO RA8835 (1 module)
- Sanyo LC7981 (13 modules)
- Sino Wealth SH1101A (2 modules)
- Sitronix ST7920 (29 modules)
- Solomon SSD1303 (1 module)
- Solomon SSD1305 (9 modules)
- Solomon SSD1325 (2 modules)
- Solomon SSD1332 (1 module)
- Solomon SSD2119 (2 modules)
- ST STV8105 (1 module)
- Toshiba T6963 (23 modules)
Somehow Intel has managed to remain competitive with TSMC in spite of poorer technology
Intel has a lot of experience in designing CPUs. A "stupid" design using the fastest technology can be worse (performance wise) than a "smart" design using somewhat older (and slower) technology.
TSMC only does chip-making they do not design, they are a foundry , so whatever chips are made by TSMC are not designed by them. The chips are designed by Qualcomm, Broadcomm and many other "fabless" semiconductor companies.
SMIC is also a foundry, just like TSMC. SMIC concentrates on older technology nodes that are "less interesting" to foundries like TSMC. A lot of chips are needed in mobile phones, cars etc. Not all of these need to be made in the latest-and-greatest fastest technology.
Realize that making a "simple" chip which can be made (or is already an existing design) in for example 14 nm (or much older, larger feature size technologies) is much, much cheaper than using the latest technology node. I mean: very often there is simply no need to use the newest technology node.
... up with TSMC if their processes are just the best?
Are they "the best"? What is "the best"? For a Soc powering the latest and greatest smartphone, indeed using the smallest manufacturing node might be essential.
But how about a chip used in a pocket calculator or microcontroller in an espresso machine? For these applications the chip needs to be cheap. A simple microcontroller, when bought in large quantities, can be had for a few cents per chip. I guarantee you that these chips will be made in an "ancient" technology, like 0.35 um CMOS (just my guess). The (at the time very expensive) equipment needed for making such chips has been written off long ago so you don't need to pay a premium price because expensive equipment is needed. That allows for chips that are extremely cheap. In many applications "cheap" is much better than "latest and greatest".
Best Answer
The main reason why ARM processors are not clocked at 4GHz is power consumption. Architecture, fabrication, etc do play a big role, but the reality is that a tablet or mobile phone needs to last as much as it can off a battery, so all those factors are designed so that power consumption will be minimized. When going for lower power consumption, you sacrifice performance because of design choices in the node, architecture etc. Higher frequency is a battery killer because:
P = CV2f
Where C is a capacitance, V is the voltage, and f is the frequency. So it varies linearly with frequency, and it's why frequency scaling is so prevalent, even in laptops.