Old Motherboads and Chipset. Motherboard Types and Models (AT, ATX) and On-Board Components.
This article was written by JMJG, to help in the study of the hardware classes taught by our company. Here you will find only some teaching materials from the classes, more information and questions with the instructor of the class. Call (11) 2308-4673 and sign up for our in-person course.
Known as Motherboard, Mainboard or nicknamed "MOBO", this component is without a doubt the most important in a computer, even more so than the processor. The Mobo receives energy from the power supply and distributes it appropriately to its cards and peripherals. It also connects the processor and puts it in communication with the RAM and data bus. It couples and interconnects external cards, hard disk, and any and all other components.
In summary, there is no digital data processed/received by the computer that does not go through Mobo.
In the Past the Mobo is big and has a discrete chips and doesn't have any aditional board inside. You must connect a Video Board or Sound, Controler in order to computer can work!
To perform complex data communication, Mobo relies on extremely complex chips (less than a processor) called Chip-Sets. To do so, each motherboard will have an Architecture, which would be exactly the right way for all peripherals to function correctly. The processor model currently dictates the architecture of the board!
In the current market, two companies dominate the processor market. Intel and AMD. But in the past,many other companies manufactured processors, Zilog (Z80), NEC,Motorola,IBM, MOS Technology,Cyrix.
For now, we are not going to talk about processors, much less the advantages and disadvantages of each one. We are not here to make comparisons, everyone has their preferences.
We must know how to choose the right Mobo, because for each type of processor, there is a correct architecture! Don't buy a Mobo without checking its compatibility with your processor first! The ideal is to define the processor and then choose the right Mobo
✏MotherBoard Types and Models
In Brazil, the best known are the old AT standard and the most current ATX standard. Let's look at the differences between them:
AT (Advance Technology) Standard
The AT standard is old and obsolete, it was widely used in computers from 1980 to mid-1990. Its architecture has many cables and connectors. It is easy to identify an AT board for two reasons:
1) It does not have any On-Board components, nor connectors on the bottom of the board.
The only connector provided is the keyboard connector! On top of that, it is the old DIN standard, there was no PS/2 or USB! Everything else must be obtained by connecting wires and cables, or even cards for resources such as (serial ports, parallel ports, video, sound, etc.)
2) Power Supply has only 2 Cables! P7 and P8.
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| Detail of the standard power connector AT |
Yes, the AT standard had a special power supply! There's no point in trying to connect new power supplies to a board like this, it must be an appropriate power supply, many ATX voltages are not even used in the AT standard. The annoying thing would be to connect it wrong, and burn the board right away! The cables can be easily damaged, leading to errors and serious problems for the technician. Attention!
A Tip here, both negative black wires must be in the midle! Detail like the last photo, if you plug wrong the motherboard will Burn 💢!
See the electrical diagram of the AT standard pinout
As we can see, the AT standard does not have automatic shutdown (power off), so to turn off the power, a power switch would have to be pressed to turn the computer on/off manually! The operating system would have to be finished first, the user would have to wait for confirmation to turn it off, and only then, turn it off! Many hard drives were damaged because users would barely wait and would turn it off without the heads being retracted.
The AT standard was discontinued because it was inadequate for a computerized machine, but it is still possible to find rarities in the Brazilian market, still using the AT standard. Be alert!
Other modern features, such as automatic cooler control (processor) did not exist. The processor cooler was connected directly to the power supply. The AT standard had constant overheating problems, due to the large amount of internal wires and cables, making it difficult for cold air to circulate inside the cases.
ATX (Advanced Technology Extended) Standard
An evolution of the AT standard, encouraged mainly by Intel. Already used after the 486, in the First Pentium 1 Line, this standard presents many improvements.
We can see that in the ATX standard, the internal cables were reduced. Now we have on-board connectors on the board that guarantee fewer cards and connectors for the same functions (mouse port, sound, network, video). With this, the overheating problem has been improved!
In the ATX standard, the keyboard/mouse have PS/2 (mini-din) connectors. Old ATX boards already had serial (RS-232) and parallel ports built into the board, dispensing with cables and connectors.
Another wonderful change was the power connector, which is now more "intelligent" and does not allow the wrong connection like AT power Supply!
Still on the energy side, a new feature was the inclusion of the automatic pulse (soft switch PWR_ON) to turn the power supply on and off, using the operating system/soft button on the panel. Now the computer can be turned off automatically, a feature not present in the AT standard. With this, functions such as hibernate/suspend in the operating system were possible.
The ATX standard also included other lower power supply voltages, dedicated to the processor and chip-sets, contributing to improved consumption, which is now much lower than in the AT standard.
The ATX Standard has many versions with improvements. The ATX 1.X and ATX 2.X with many improvements.
The Last ATX Standard has a +12V Line dedicated to Processors and special connectors to Video Boards.
Plate Size (Case Dimensions)
The ATX standard gave rise to many other versions, but don't worry, they are only about the size of the plate, as they all follow the ATX standard faithfully. Be careful to see if the desired case accepts the motherboard you want to install. Below is a table with the size of ATX plates and their commercial names.
The ATX and Micro-ATX standards are very common for use in desktops (personal computers). The other standards are used in corporate environments, you won't see them much.
For gamers and enthusiasts, it's best to buy a case that supports ATX boards, Micro-ATX ones have fewer expansion slots.
Motherboard Slots (Expansion Buses)
To expand the motherboard's resource capacity, it is possible to connect dedicated cards, to obtain better performance or even make up for the lack of some non-existent resource.
Many motherboards were completely off-board (the case of standard AT boards), so to get video, sound, etc. users had to fit the boards into specificexpansion slots.
ISA Expansion Slot (Industry Standard Architecture)
This bus used 8 bits for communication that was later expanded to 16 bits like the picture above. The 8 Bits has only the first bus in left side, and will be used in XT 8088 boards. When the AT 286 computers arrived in market, the 16 Bits must be used, then ISA have been extended to Right Side with more pins! 8 Bits Boards can be plugged in 16 Bits Slots but not the inverse! A 16 Bits boards can not plugged in 8 Bits Slots like XT motherboard!
This bus is no longer used today (only a few applications still run on ISA), due to its low performance. In Pentium 2/3 a maximum of 3 ISA slots can exist on a motherboard. It is rare to find Pentium 4 board with this bus.After Dual Core processors the ISA Standard is dead in motherboards!
PCI Slot (Peripheral Component Interconnect)
This is perhaps the most famous and used expansion bus known to the entire world. Based on the IBM-PC architecture, it was created by INTEL in 1992 for the Pentium line, thus retiring the ISA due to its low performance. In some boards of AT 486 like 486 DX2/DX4 the PCI Slot is already present!
It operates with 32 or 64 bits of transfer (133MB/s max) and accepts up to 5 buses on the Mobo. The advantage is that DMA, IRQ and other parameters are configured automatically (Plug&Play).
Hundreds of cards with a wide range of functions (video, sound, network, parallel, serial, capture, etc.) were produced using the PCI standard. There are still some modern Mobos that have at least 1 PCI slot (to support that old and beloved card).
However, the PCI slot is no longer used by the industry in nowadays. It is being replaced by another, more advanced standard called PCI-E (PCI Express). But be aware that you will inevitably come across this slot in your life, due to the huge range of cards that were manufactured using this standard.
AGP (Accelerated Graphics Port) 3D video (games and advanced graphics)
More advanced video cards with style processing chips (ATi Radeon/Geforce) the famous cards 3D accelerators, needed more bus speed, something that common PCI slots could not provide. With that, the AGP standard was created, exclusively to connect accelerator video cards!
Created by Intel in 1997 to be used in a Pentium 2, it became the market standard. The AGP 1X can transfer at rates of up to 266MB/s, twice that of normal PCI.
After 2003, with more advanced graphics chips, the industry improved the AGP standard, and higher speeds emerged AGP2X - AGP4X -AGP8X.
AGP8X was the best video standard achieved, reaching up to 2133MB/s and allowing the use of shared RAM.
In 2005, Intel itself discontinued this bus for an improved one. Currently, no modern video card uses AGP buses, and no modern Mobo has this connector. However, due to the wide range of cards produced, you may come across this bus one day.
Video cards connected via AGP slot are much better than those connected via normal PCI, which generally do not exceed VGA resolution. In AGP the video board can be DVI connect beyond VGA!
PCI-E (The new slot standard - Current)
In 2004, Intel introduced the bus PCI-E as a replacement for slots AGP and PCI. With that, it became the industry standard for current expansion cards.
All current Mobos have PCI-E slots inside them. Just like AGP, PCI-E has a number to indicate its speed.
PCI-E 1X, 2X,4X,8X,16X and 32X
PCI-E 1X can transfer up to 6X133Mhz much faster than a traditional PCI.
As you can imagine, a 16X slot is much faster still, reaching up to 4GB/s. That's why PCI-E 16X has become the industry standard for new video accelerator cards nowadays.
The 32x 8GB/s standard is not yet being used by video cards.
Due to the low voltages, it is more immune to noise and can therefore achieve very high transfer rates.
Another advantage is that in PCI-E the cards have an exclusive path to the chipset, in PCI the cards were all in parallel.
A new feature is that cards with lower speeds can be connected to higher speed slots.
Ex:
A 1X PCI-E can be connected to a PCI4X slot
An 8X PCI-E can be connected to a PCI16X slot
With this, we gain ease and practicality, ending the famous compatibility confusion.
A higher speed PCI-E can NEVER be plugged into a lower speed PCI-E slot, for the simple reason. It won't fit!
Physically, the more X, the longer the connector length, so there is no error.
CHIPSET (North and South Bridge)
The famous Mobo Chipset is a very special integrated circuit, which is what connects the processor to the other peripherals. It is as if it were the manager or coordinator of the team, leaving the president (CPU) free to do other activities.
👉Northbridge: It connects the processor (CPU) and the RAM, offering an exclusive high-speed channel. Other high-speed channels are also controlled by this chipset. For many years, it was integrated into the Mobo itself, but some architectures (AMD) already used the Northbridge chipset integrated into the processor itself.Currently, both Intel (Core I) and AMD (FX, Sempron, Athlon,Ryzen) processors have Northbridge integrated into the processor. So don't expect to see it on the Mobo!
👉Southbridge: Chip integrated into the motherboard (the only one currently) that controls all other peripheral communications. On-board devices (sound, network), SATA, IDE connections, and everything else. All current motherboards have this chipset, only older motherboards have 2 (north+ south).
Internal Controllers (OnBoard)
When we buy a current Mobo, it is common for some circuits to be onboard. Generally these circuits are the SOUND and the Network card (internet). Depending on the processor installed on the motherboard, the onboard Video may also be available.
Sound: The vast majority of boards come with an ALCXXXXX or similar controller installed. It offers sound in up to 5.1 channels of good quality, sufficient and reasonable for the vast majority of the public. But if you are a demanding user, gamer or even appreciate superior sound quality, it is better to install a dedicated board (offboard) such as a SoundBlaster. The same trademark like great Old Sound Cards in AT x86 lines!
Network: Required for internet connection (RJ45) most Mobo Current ones use the RTLXXXX controller chip or similar. With a standard 100/1000GB/s connection, this controller is sufficient for all users. Except in cases where you want 2 network cards or +, or when the internal card burns out (lightning, etc.), you can install another external network card via PCI or PCI-E. The same case if you desire a Wi-Fi board must connect into PCI-e slot!
Video: The most controversial of the cards, in which many defend the GPU and others the APU. I personally see more advantages in the GPU (offboard) but as I said it depends on taste and usage preferences. To enjoy the onboard video, you must install a processor that has an APU! Otherwise, you will only be able to have video with an offboard card.
Any time you install an offboard video card via PCI-E/AGP, the Mobo will automatically turn off the internal APU, freeing up the resources as expected.
Only special Mobo boards allow SLI or CroosFireX to add 2 GPU, improving processing power!
Standard Connections (Rear View)
Many current Mobos have rear connections like the ones in theabove. Here in Brazil, most cards have (USB, USB3.0, VGA Video, Network, SOUND 5.1 (green, blue, red).
Panel Connections (PanelSW, Led/ power /reset)
It is also necessary to make some connections between the Mobo and the case. Front USB, sound connectors, power buttons, reset buttons and signaling LEDs are the common ones.
See the pattern
Front USB: Check the Mobo manual for the correct pinout. If it has a standard connector like in the photo above, connect it to the Mobo as indicated in the manual, be careful, there are adequate polarity and voltages. An incorrect connection can burn the USB port or peripherals connected to it.
H.D.D Led: Hard disk activity indicator light - lights up when reading/writing. Connect as indicated in the manual, there are polarities + and -, connecting it incorrectly will cause the light to not light up or burn out.
Power Led: Power/hibernate or suspended status indicator light. - Lights up when the computer is on, or flashes to signal a special status. Turns off when there is no power. Connect as indicated in the manual, has polarity + and -, connecting it incorrectly will cause the light to not light up or burn out.
Power SW: On/Off button. Connect as indicated in the manual, there is no polarity. The cabinet button must be a momentary contact switch style, it cannot be locked in the on state!
Reset SW: Reset button. Used to reset the machine (restart) without turning off the power. Connect as indicated in the manual, there is no polarity. The cabinet button must be a momentary contact switch style, it cannot be stuck in the on state!
Take advantage and ask all your questions during the classes.
See you next time.👊😎
JMJG (Electronic Eng- Hardware Instructor)
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