Explaining PCIe Slots

[Music] welcome to another video from explaining computers comm this time I'm going to talk about the PCIe slots that we use to connect graphics cards and other expansion cards to our computer motherboards now I'm going to start out with a little bit of the history of motherboard slots to place PCIe in context and that on move on to talk about PCIe lanes and slot sizes and versions and all that other handy to know kind of stuff in the 1980s early IBM pcs came with expansion stops known as the XT or 18 thus however these were later renamed ISA or industry standard architecture slots and here we've got a 1989 motherboard with eight is n slots and think about is a slots is they were used to connect almost everything to the computer motherboard not just graphics cards but all the ports on the computer or the storage interfaces you had a card for example like this one which gives you the disk interfaces and parallel ports and serial ports that we can find them there so everything connected initially via iose slots now the only problem was as PC technology advanced is a start weren't fast enough for the latest graphics and other cards and therefore an extended version of is a called a is a was introduced in 1988 as well as an interface called the VESA local bus all VLB in 1992 however neither of these became that popular it's in 1992 we also saw the introduction of the peripheral component interconnect or PCI expansion slot as we can see on this 1997 motherboard that sometime we had motherboards with both the PCI slots we got four of these here as well as a is a slots and this board also has an AGP slot an accelerated graphics port slow and this was a graphics card only interface on motherboards this was launched in 1996 and it evolved into many different incompatible versions for example here we've got another motherboard which has got an AGP start and fiver PCI slots as you can see this is clearly a different type of slot to the previous AGP port we saw on the previous board it's longer this is an AGP x 8 slot an AGP Pro slot and back in the 90s when we had all these AGP ports and they constantly revolving now to be very careful to get the right graphics card to match the right slot they had different voltages it wasn't that difficult to blow things up by putting the wrong AGP card into the wrong kgp port however in 2004 things started to get easier with a launch of PCIe or peripheral component interconnect Xpress as a higher speed version of PCI and as we can see on this far more recent motherboard PCIe thoughts can come in different sizes so here for example we've got 3 PCIe x 1 slots and one PCIe x 16 slot the sort of slotted lan we put a graphics card in and to explain the differences between these type of slots and now need to tell you about how PCIe handles data data is communicated to and from PCIe slots in what are called lanes and so I thought it'd be nice to imagine that data as a fleet of little cars and so here we have one lane of cars traveling to a PCIe slot it's eight times one stop because as one lane of cars and each car here represents a fixed quantity of data but if we want to get more data to the card and we can't increase the speed of the cars what we can do is to add more lanes so if we increase number of lanes by a factor of four when other words would move to PCIe times four we get four times as many vehicles and hence four times the data transfer rate being accommodated and if we increase again to PCIe times 8 and then PCIe times 16 we double and double again the data is fruitful to the PCIe slot without having to increase the speed of its underlying electronics now although PCIe increases speed by adding lanes since 2004 that PCIe standard has been upgraded several times with the different versions known as PCIe 1.0 2.0 3.0 and 4.0 each of these has a lane speed which is roughly double that of the previous generation so making our little cars move twice as fast with each PCIe version upgrade here in this table you can see all of the theoretical speeds attainable with all overcurrent PCIe versions using one four eight or sixteen lanes note that 32 times PCIe slots and expansion cards with 32 lanes do exist but they're very rare indeed note also with a new PCIe 5.0 standard is expected to be finalized in 2019 with likely speed as shown in italics in the last line of the table and yes a 16 times PCIe 5.0 card will be very fast indeed in most instances the physical size of a PCIe slot indicates his number of lanes so for example if we look at this fairly modern motherboard which has got one two three four PCIe slots and three PCI slots you'll see that we've got a slot here and here which our PCIe times one they've got one lane and we've got two slot here which is a PCIe x 16 slot and this has got a 16 lanes this is where you put your graphics card on this board however if we look at the slot down here you might say what's the same size as this one this is a PCIe x 16 size slot however this is actually a PCIe x 4 slot it's only got four lanes inside this actual physically 16 x slot and so you need to look very carefully at your motherboard when choosing and fitting PCIe devices to make sure you get the best slot for your expansion card so here if we look very closely we can see this second PCIe x 16 length slot is labeled PCIe x 4 and if we look very closely indeed we could also notice it only has electrical pins running for the first quarter of its length what are the great things about PCIe is the high level of compatibility across versions and slot sizes so for example on this motherboard the PCIe slots are pcie 2.0 this is a time 16 pcie 2.0 slot but here I've got a graphics card which is pcie 3.0 but this would work absolutely fine on this board we could plug this in here like this go in there and er click into place and this would run at pcie 2.0 speed and similarly if this was say i pcie 2.0 card and it was a pcie 3.0 slot again things would work at the pcie 2.0 speed so you can mix and match across different versions and things will always run at the lower speed it weaves the card of a stock you're using another important thing to note is that it's possible to use an expansion card who requires a low number of lanes in a PCIe slot with a higher number of lanes so if we for example take this card out of here this is a time 16 card at a time 16 slot that obviously works fine but here i've got a USB 3 adapter which is a PCIe card a PCIe x one card and this would normally go into a PCIe x 1 slot to put it in somewhere like that and that would work fine but you could if you wanted to put this into there x 16 stocks we've got a x 1 card in the time 16 stock and that would work absolutely fine this card needs one lane it would take just one lane from this card it would waste all yours that would work and you might be thinking that's absolutely ridiculous why would you do that on this motherboard clearly this would be ridiculous thing to do this x 1 card should go into a title 1 slot but there are situations this can be very useful so for example if we look at this motherboard this is a mini ITX motherboard a small form-factor motherboard it's only got one slot 8 times 16 PCIe slot and therefore here if we wanted to fit something like our USB adapter we have no choice we'd have to put it in here because there's no other option and again this is a bit of the cylinder shame we're wasting all these lanes but it's good to know you can put a lower Lane card into a high lane slot because in some circumstances it's a very useful thing to do now the other way around it's sometimes possible to fit a Highland card into a lower lane PCIe slot so for example going back to this motherboard you might remember here the x 4 slot is x 16 in lengths so we could fit a x 8 card or a x 16 card into this slot and it would work if only at times for speed now this point made it's important to be clear but not all lower lanes slots will accept a higher lane card and looking back at this motherboard you can see why there are physical ends on these x 1 slots for example we stopped it happening so I bring in the graphics card here this is the 16 times cog I clearly couldn't be fitted it wouldn't physically go into that slot but you can get what are called open-ended slots so if we look at our final board of the video this is a rock pro 64 single board computer and it's got a PCIe x 4 slot but it's open-ended so we could potentially take here or 16 x card and plug it in and it would fit whether it work on this particular single board computer would depend on drivers and stuff but hopefully we've proved a principle you can sometimes fit for example a time 16 card into a times 4 slot the PCIe standard is I think one of the unsung heroes of modern desktop computing and I hope you found this video useful to learn more about PCIe slots and how they can be used certainly I've had a great time putting this video together because I've had to get out lots of old motherboard like this one and that's made me think maybe I should make a video all about the history the evolution of the technologies on PC motherboards that might make an exciting video anyway that will happen I think in the future but it's now stiller to present and if you enjoyed this video please press that like button if you haven't subscribed please subscribe and I hope to talk to you again very soon [Music] you

Channel: ExplainingComputers

Views: 1,350,436

Rating: 4.9518332 out of 5

Keywords: PCIe slots, PCIe, slot, slots, PCIe expansion slots, explaining PCIe, PCIe tutorial, tutorial, Christopher Barnatt, Barnatt, graphics card, graphics card slot, PC expansion slots, PCIe interface, motherboard slots, motherboard, PCIe 3.0, PCIe 4.0, PCIe 5.0, PCI-e, PCI-e slots, ISA, AGP, AGP slot, AGP slots, ISA slot, ISA slots, PCI slot, PCI, PCI slots

Id: PrXwe21biJo

Length: 11min 9sec (669 seconds)

Published: Sun Sep 16 2018