Photo: In this blog post, we'll go over the differences between PCIe Gen 4 and PCIe Gen
3. We'll also☀️ discuss whether it's time for an upgrade.
Table of Contents
Make no
mistake, PCIe 4.0 is twice as fast as PCIe 3.0.
But☀️ whether it’s time to upgrade your
hardware to support PCIe Gen 4 is a different matter altogether.
In this blog post,
☀️ we’ll discuss the speed differences between both generations and address backward and
forward compatibility.
Then, we’ll touch on whether upgrading is☀️ right for you.
You can
read more about PCI Express, how it works and its previous generations below, or you
can☀️ skip right to the speed differences between PCIe 4.0 and PCIe 3.0.
Photo: Seven
PCIe slots showcased on a Trenton Systems'☀️ dual Xeon Motherboard. This particular
motherboard incorporates three PCIe 3.0 x16 slots and four PCIe 3.0 x8 slots for super
☀️ fast speeds and versatile system expansion. At Trenton Systems, we design our own
boards to fit your application-specific needs. Get☀️ in touch with us today.
What is PCI
Express?
The Peripheral Component Interconnect Express (PCI Express or PCIe) is a
high-speed interface☀️ standard for connecting additional graphics cards (GPUs), Local
Area Network (LAN) ports, NVME solid-state drives (SSDs), Universal Serial Bus (USB)
☀️ ports and other hardware to a computer’s motherboard.
This is accomplished using
expansion cards, also known as add-on cards.
Simply put, the☀️ PCI Express interface
allows for the expansion of a motherboard beyond its default GPU, network and storage
configurations.
The Peripheral Component☀️ Interconnect Special Interest Group (PCI-SIG),
comprised of big-name technology companies like Intel, IBM, Dell, HP, AMD and NVIDIA,
introduced the☀️ first generation of PCI Express, entitled PCIe 1.0, in 2003.
PCIe 2.0
and 3.0 were released in 2007 and 2010, respectively.☀️ PCIe 4.0 came out in 2024, and
PCI-SIG’s latest generation, PCIe 5.0, debuted in 2024.
The PCI Express interface is
actualized☀️ through PCIe slots, which vary in type depending on a motherboard's
chipset.
The slots differ in both length and speed based☀️ on their number of lanes (at a
minimum, one lane, and at a maximum, 16 lanes).
Slots are available in one-lane,
☀️ two-lane, four-lane, eight-lane and 16-lane configurations, usually expressed as PCIe
x1, x2, x4, x8 or x16.
Photo: A motherboard showcasing the☀️ different PCIe slot
configurations, as well as Peripheral Component Interconnect (PCI) slots, which are now
obsolete. Credit: CCBoot
For example, PCIe☀️ 3.0 x4 refers to a Gen 3 expansion card or
slot with a four-lane configuration.
Likewise, PCIe 4.0 x16 refers to☀️ a Gen 4 expansion
card or slot with a 16-lane configuration.
And so on.
Each new PCI Express generation
doubles the amount☀️ of bandwidth each slot configuration can support. That's why the
configurations are expressed in multiples of two.
PCI Express: Unidirectional Bandwidth
☀️ in x1 and x16 Configurations Generation Year of Release Data Transfer Rate Bandwidth x1
Bandwidth x16 PCIe 1.0 2003 2.5☀️ GT/s 250 MB/s 4.0 GB/s PCIe 2.0 2007 5.0 GT/s 500 MB/s
8.0 GB/s PCIe 3.0 2010 8.0 GT/s 1☀️ GB/s 16 GB/s PCIe 4.0 2024 16 GT/s 2 GB/s 32 GB/s
PCIe 5.0 2024 32 GT/s 4 GB/s 64☀️ GB/s PCIe 6.0 2024 64 GT/s 8 GB/s 128 GB/s
Table:
PCI-SIG introduced the first generation of PCI Express in 2003.☀️ With each new
generation comes a doubling of data transfer rate and total bandwidth per lane
configuration, the latter of☀️ which is expressed in both unidirectional and
bidirectional measurements, depending on the source. To find the total unidirectional
bandwidth for☀️ each lane configuration, simply multiply the x1 bandwidths listed in the
table above by two, four, eight or 16. Multiply☀️ the number resulting from that
calculation by two to calculate total bidirectional bandwidth. Source: PCI-SIG
For
example, PCIe 1.0 has a☀️ 250 MB/s bandwidth in the one-lane configuration, a 0.500 GB/s
bandwidth in the two-lane, a 1 GB/s bandwidth in the☀️ four-lane, a 2 GB/s bandwidth in
the eight-lane and a 4.0 GB/s bandwidth in the 16-lane.
It’s important to note as☀️ well
that these lane-specific bandwidths are often doubled to account for bidirectional
travel, or data traveling to and from each☀️ lane.
Furthermore, each new generation of
PCIe typically doubles its predecessor’s data rate and bandwidth for each
configuration.
For example, PCIe 1.0☀️ has a 2.5 GT/s data rate and a 250 MB/s bandwidth
in the one-lane configuration, while the one-lane configuration for☀️ PCIe 2.0 supports a
5.0 GT/s data rate and a 500 MB/s bandwidth, and so forth.
But PCIe 1.0 and PCIe☀️ 2.0
are outdated.
Today, PCIe 3.0 is a motherboard standard, at least until the industry
universally adopts PCIe 4.0 and eventually☀️ PCIe 5.0. And by that point, PCI-SIG will
have rolled out the next generation, PCIe 6.0, which is expected in☀️ 2024.
As with any
new technology, it can take computer hardware manufacturers some time to begin
standardizing their motherboards with the☀️ latest PCI Express generation.
How fast is
PCIe 4.0 vs. PCIe 3.0?
PCIe 4.0 is twice as fast as PCIe 3.0.
PCIe 4.0☀️ has a 16 GT/s
data rate, compared to its predecessor’s 8 GT/s. In addition, each PCIe 4.0 lane
configuration supports☀️ double the bandwidth of PCIe 3.0, maxing out at 32 GB/s in a
16-lane slot, or 64 GB/s with bidirectional☀️ travel considered.
Unidirectional
Bandwidth: PCIe 3.0 vs. PCIe 4.0 PCIe Generation x1 x4 x8 x16 PCIe 3.0 1 GB/s 4 GB/s☀️ 8
GB/s 16 GB/s PCIe 4.0 2 GB/s 8 GB/s 16 GB/s 32 GB/s
Table: The speed differences
between PCIe 4.0☀️ and PCIe 3.0 in each lane configuration.
Let’s use the 16-lane slot
configuration to put the speed differences between PCIe 4.0☀️ and 3.0 into perspective
and make all this computer lingo a little more relatable.
For the purposes of this
analogy, we’ll☀️ employ unidirectional bandwidth for both generations.
Photo: Aerial
drone photograph of traffic in a metropolitan area, used to illustrate PCIe
lanes.
Imagine☀️ 16 lanes of cars (data) traveling in 16 adjacent lanes (configuration)
on the major PCIe 3.0 Highway (generation).
The cars are☀️ traveling at the posted PCIe
3.0 speed limit of 15 miles per hour (bandwidth).
Several miles in the opposite
direction, however,☀️ the state (PCI-SIG) has just opened the PCIe 4.0 Highway and
doubled the speed limit.
The cars on this highway are☀️ traveling faster at the newly
posted PCIe 4.0 speed limit of 30 miles per hour.
And a couple of years from☀️ now, cars
will be cruising on the PCIe 5.0 Highway, where they’ll be allowed to travel at a
posted speed☀️ limit of 60 miles per hour.
And so on with each new PCI Express generation
that PCI-SIG introduces.
Photo: Wooden backward and☀️ forward signposts. Credit:
Hashnode
Are PCIe 4.0 and PCIe 3.0 backward and forward compatible?
Both PCIe 4.0 and
PCIe 3.0 are backward☀️ and forward compatible.
Remember those high-speed components
(GPUs, NVME SSDs, etc.) that use PCIe slots to interface with the motherboard and
☀️ provide additional functionality?
Thanks to backward and forward compatibility, the new
can be used with the old (backward compatibility), and the☀️ old can be used with the new
(forward compatibility).
For example, a PCIe 4.0 graphics card can be inserted into a
☀️ motherboard’s PCIe 3.0 slot; however, the Gen 4 card’s bandwidth would be bottlenecked
by the Gen 3 slot’s bandwidth limitations.
Similarly,☀️ a PCIe Gen 3 graphics card can be
inserted into a motherboard’s PCIe Gen 4 slot, but the Gen 3☀️ graphics card will be
incapable of fully utilizing the higher bandwidth capabilities of the Gen 4 slot due to
the☀️ card’s intrinsic bandwidth limitations.
Photo: Connectors of different-sized PCIe
expansion cards. Credit: How-To Geek
Your expansion card doesn’t have to be installed
☀️ on a slot with the same number of lanes, either.
For example, a PCIe 4.0 SSD with four
lanes can be☀️ inserted into a x16 slot.
But the inverse doesn’t work.
So, a PCIe 3.0 x16
graphics card won’t fit in a x1,☀️ x2, x4 or x8 slot.
In short, the slot into which the
expansion card is being inserted must have an equal☀️ or greater number of
lanes.
Otherwise, the card can’t physically be inserted into the slot.
Photo: There are
a few things to☀️ keep in mind when choosing PCIe 4.0 SSDs and PCIe 4.0 GPUs, mainly the
population and PCIe generation of your☀️ motherboard's PCIe slots.
How does PCIe 4.0
influence SSD and GPU selection?
As previously mentioned, PCIe 4.0 is backward and
forward compatible.☀️ So, you can insert a PCIe 4.0 GPU into a PCIe 3.0 slot, but you'll
be bottlenecked by the bandwidth☀️ limitations of Gen 3. In other words, you won't be
able to take full advantage of the increased speeds of☀️ that awesome PCIe 4.0 GPU. The
same goes for PCIe SSDs, so keep this in mind when you're shopping around.
Photo:☀️ An
512GB PCIe-based NVMe M.2 SSD
PCIe 4.0 SSD
If you're in the market for a high-speed
PCIe 4.0 SSD, such as☀️ an PCIe 4.0 NVMe SSD, take comfort in knowing that you'll have
the access to the latest and greatest that☀️ the PCIe specification has to offer with Gen
4, including increased data transfer rates, bandwidth, and decreased latency on the
☀️ PCIe bus. This is assuming, of course, that your motherboard is equipped with PCIe Gen
4 slots into which you☀️ can insert these PCIe 4.0 SSDs.
Remember: the PCIe generation
used on your motherboard's PCIe slots determines the data transfer rate☀️ and bandwidth
of whatever expansion card you insert into it. PCIe 4.0 SSDs can only match the speeds
of a☀️ PCIe 4.0 slot, and PCIe 3.0 SSDs can't leap in data transfer rate and bandwidth to
PCIe 4.0. So, if☀️ you insert any PCIe 4.0 SSDs into previous-generation PCIe slots, you
won't receive the bandwidth and data transfer rate increases☀️ you're expecting from PCIe
4.0, only the bandwidth and data transfer rate of that slot's particular PCIe
generation.
There's also widespread☀️ use of PCIe 4.0 NVMe SSDs, specifically, mainly
because NVMe has become the industry standard for PCIe SSDs, but also☀️ because NVMe SSDs
reduce power consumption, further reduce latency, and incorporate 1,000,000
input/output operations per second (IOPS) compared to a☀️ SATA SSD's 200,000. This offers
an obvious performance increase to users shopping around for PCIe 4.0 SSDs.
Photo: A
GPU
PCIe 4.0☀️ GPU
The same bandwidth and data transfer rate rules that apply to PCIe 4.0
SSDs apply to PCIe 4.0 GPUs. If☀️ you purchase a PCIe 4.0 GPU for your system and seek to
benefit from PCIe Gen 4's performance increases and☀️ reduced latency, then your
motherboard will need to be populated with a PCIe 4.0 slot of appropriate lane size to
☀️ support your PCIe 4.0 GPU.
Otherwise, your PCIe 4.0 GPU will be stuck with
previous-generation speeds, and who wants to purchase☀️ a new, shiny, expensive PCIe 4.0
GPU without, you know, reaping the benefits of PCIe 4.0?
We're starting to see more☀️ and
more PCIe 4.0 GPUs pop up on the market, and it's clear that they'll play a pivotal
role in☀️ streamlining and boosting the performance of data-intensive artificial
intelligence (AI) and machine learning (ML) applications of the future. But the☀️ last
thing you want to do is purchase one for your system and find out it's useless.
Photo:
Depending on the☀️ data transfer rate and bandwidth needs of your program or application,
it may be time to upgrade to PCIe 4.0.
Is☀️ upgrading to PCIe 4.0 worth it?
PCIe 4.0
supports double the bandwidth of PCIe 3.0, so if you want to take☀️ advantage of the
bandwidth capabilities of that PCIe 4.0 expansion card you just purchased, then you’ll
need PCIe 4.0 slots☀️ on your motherboard.
It’s as simple as that.
But if you’re
comfortable with a certain degree of bandwidth limitation and don’t want☀️ to spend the
money to upgrade to a PCIe 4.0 motherboard, then upgrading to Gen 4 probably won’t be
worth☀️ it to you.
Plus, if you’re working with PCIe 3.0 expansion cards and slots,
anyway, and they’re providing you with the☀️ speeds that your application needs, then
don’t worry about upgrading to Gen 4.
When deciding whether to upgrade, ask yourself
two☀️ key questions:
Are my current PCI Express cards and slots providing me with the
speeds I need for my application? If☀️ yes, don’t upgrade. If no, consider upgrading.
Will my application need a bandwidth boost soon to keep up with its☀️ increasing
input/output workload? If yes, consider upgrading. If no, don’t upgrade.
Contact
Trenton Systems today or chat with a member of☀️ our team to discuss whether upgrading is
right for you.
Be sure to subscribe to our blog to keep up with☀️ the latest
updates.
Trenton Systems creates rugged computer systems to help customers around the
world meet their rugged computing needs. We☀️ stress-test our computer systems to the
max, ensuring that customers can carry out industry-specific operations comfortably,
effectively and smack dab☀️ in the middle of the world's harshest conditions. In other
words, we stress so you don't have to.
