AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |
Back to Blog
Smallest transistor intel9/9/2023 The practice of counting empty transistor sites may seem like an exaggeration of the real transistor count, but there are some good reasons to count this way. Given the potential uncertainties in counting, it's not surprising that Intel rounded the numbers to the nearest thousand. The published number of physical transistors in the 8086 is "approximately 20,000".įrom my counts, the 8086 has 19,618 physical transistors and 29,277 transistors when including empty sites. The 8086 is commonly described as having 29,000 transistors when including empty sites in ROMs and PLAs that potentially could have a transistor. The number of transistors in a chip is harder to define than you might expect. I count 2689 depletion-mode transistors, but you could exclude them from the count as not "real" transistors. The 8086 is built with NMOS logic which builds gates out of active "enhancement" transistors as well as "depletion" transistors which basically act as pull-up resistors. Should these be excluded from the transistor count? Physically they are transistors but functionally they aren't. Some are input protection diodes, while others are used in the charge pump for the substrate bias generator. The 8086 has about 43 transistors wired as diodes for various purposes. Driver transistors next to the pad are constructed from multiple transistors in parallel. One could argue that it shouldn't be counted because filling in these transistors might run into problems.Īn output pad with a bond wire attached. I'm counting its "potential" transistors, but It is essentially a grid, but has been "squeezed" slightly to optimize its layout, making it slightly irregular. The photo below shows a closeup of the constant ROM. This is harder than you might expect because the smaller ROMs, such as the constant ROM, I counted the number of transistor sites in the various ROMs and PLAs in the 8086 chip. To get a transistor count that includes empty sites, This number is close to my count of 19,618. That paper gives the approximate number of (physical) transistors in the 8086 as 20,000. "This is 29,000 transistors if all ROM and PLA available placement sites are counted." I found an Intel history that confirmed that the 8086 transistor count includes potential sites, saying Green T's indicate transistors, while red X's indicate positions with no transistor. Thus, depending on the data encoded into the ROM during manufacturing, the number of transistors varies.Īn extreme closeup of the microcode ROM. Transistor gates are formed where vertical polysilicon lines (removed for the photo) passed over the doped silicon. The empty regions are undoped silicon, while the other regions are doped silicon. The photo below shows a closeup of the silicon layer for part of the 8086's microcode ROM. In the 8086, transistors are created or not through the pattern of silicon doping. ROMs are typically constructed as a grid of cells, with a transistor at a cell for a 1 bit, and no transistor for a 0 bit. What are these potential transistor sites? Places that could have transistors, but might not.Ī PLA (Programmable Logic Array) has similar issues the transistor count depends on the desired logic functions. Since marketing doesn't want to publish varying numbers depending on the number of 1 bits and 0 bits, they often count ROM sites: The explanation is that when manufacturers report the transistor count of chips, typically often report "potential" transistors.Ĭhips that include a ROM will have different numbers of transistors depending on the values stored in the ROM. What accounts for the 9382 missing transistors? However, I have traced out every transistor from die photos and my count is 19,618. Most sources say that this processor has 29,000 transistors. How many transistors are in Intel's 8086 processor? This seems like a straightforward question, but it doesn't have a straightforward answer.
0 Comments
Read More
Leave a Reply. |