hpr-knowledge-base/hpr_transcripts/hpr3633.txt

Episode: 3633
Title: HPR3633: The collective history of RAID controller brands
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr3633/hpr3633.mp3
Transcribed: 2025-10-25 02:32:43

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This is Hacker Public Radio Episode 3633 for Wednesday the 6th of July 2022.
Today's show is entitled, The Collective History of Raid Controller Brands.
It is hosted by JWP and is about 14 minutes long.
It carries a clean flag.
The summary is, Computer Memory is a generic term for all of the different types of data
storage technology that a CE.
Good day.
My name is JWP and today I want to talk about the types of computer memory.
Okay.
So when I think about memory, I normally think about random, but it's not the case.
Computer Memory is a generic term for all the types of data storage technology that
the computer may use including RAM, ROM and flash memory.
Some types of computer memory can be very fast, meaning that the central processing unit
or CPU can access the data stored there very quickly.
Other types are designed to be very low cost so that large amounts of data can be stored
there economically.
Another way the computer memory can vary is that some types are non-votl.
This means they can store the data on a long-term basis when there is no power.
And some types of votl, which means they're faster, but they lose all their data when
the power is switched off.
A computer system is built using a combination of these types of memory and the exact configuration
can be optimized to produce the maximum data processing speed or the minimum cost or
some compromise in between the two.
So what are the different types of computer memory?
Although many types of memory in a computer exist, the most basic distinction is between
primary memory, often called system memory, and secondary memory, which is more commonly
called storage.
The key differences between the primary and secondary memory is speed of access.
So primary memory includes ROM and RAM and is located close to the CPU on the computer
motherboard, enabling the CPU to read data from the primary memory very quickly indeed.
It's used to store data at the CPU, which immediately, with the CPU needs immediately,
so that it does not have to wait for it to be delivered.
Secondary memory by contrast is usually located within a separate storage device, such as
a hard disk or solid state drive, which is connected to the computer system either directly
or over the network.
The cost per gigabyte of secondary memory is much lower, but the reading ride speeds
are significantly slower.
So primary types of memory, so you have RAM and ROM, okay?
So RAM is random access memory and ROM is read only memory.
So let's look at in-depth at both these types of memory.
RAM computer memory, the RCOM RAM stems from the fact that data is stored in a random access
memory can be accessed as the name suggests, and any random order, or put another way, any
random bit of data can be accessed just as quickly as another bit.
The most important thing to understand about RAM is that RAM memory is very fast and can
be written to as well as read.
It's volatile so that all the data stored in RAM is lost when it loses power, and finally,
it's very expensive compared to all types of memory, all types of secondary memory in
terms of cost per gigabyte.
It is because of the relative high cost that RAM is compared to secondary storage types
that most computers use both primary and secondary memory.
So I work with in-memory databases, and I can assure you that the largest hardware
cost in the computer is the RAM.
The CPU is second, but it's only a fraction of what the RAM is.
So data that's required for intimate processing is moved to RAM where it can be accessed
and modified very quickly so that the CPU is not kept waiting.
This is what the in-memory database is so great is that you can do analytical stuff
or you can do queries, and it's just really, really fast.
When the data is no longer required, it's shutted into out to lower, cheaper, memory
subsystem, and the RAM space is freed up, and it can be filled with the next chunk of
data that's about to be used.
So there are several types of RAM.
So you have DRAM and SD RAM.
I haven't used SD RAM in a long time.
So DRAM is what we use at work, and it comes in a variety of flavors.
So DRAM stands for dynamic RAM, and the most common type of RAM used in computers, the
oldest type is a single data rate or SDR RAM.
The newer computers use faster dual-rate DDR RAM, and DDR comes in several versions including
DDR2, DDR3, and DDR4, which offers better performance and is more energy efficient than
DDR.
However, different versions are incompatible, so it's not possible to mix DDR2 with
DDR3 on a computer system.
DRAM consists of transistor, of a transistor, and a capacitor, and each cell.
OK, so the other type is SRAM, which stands for static RAM, and it's a particular type
of RAM, which is faster than DRAM, but more expensive and bulkier.
Having six transistors for each cell, for those reasons SRAM is generally used as a data
cache within a CPU itself, or as RAM in a very high-end computer systems, a small SRAM
cache of most of the immediate leading data can result in significant speed improvements.
OK, the key differences between DRAM and SRAM is that SRAM is much faster than DRAM, and
these perhaps two or three times faster, but it's more expensive than bulkier.
SRAM is usually available in megabytes, or as DRAM is purchased in gigabytes.
DRAM uses more energy than SRAM because it needs to be refreshed to maintain data
integrity, while SRAM, though volatile, does not need constant refreshing when it's powered
up.
So, let's move on to ROM computer memory.
ROM stands for read-only memory, and the name stems from the fact that while data can
be read from this type of computer memory, data cannot normally be written to it.
It's very fast type of computer memory, which is usually located close to the CPU on
the motherboard.
ROM is a type of non-vautal memory, which means the data store in the mod persists, even
the memory when it receives no power, for example, the computer shut off, in that sense
it's similar to secondary memory, which is used for long-term storage.
When the computer is turned on, the CPU can begin reading information stored on ROM without
the need for drivers or other complex software to communicate with it.
The ROM usually contains a bootstrap code, which is a basic set of instructions that the
computer needs to carry out to become aware of the operating system stored in the secondary
memory, and to load parts of the operating system into the primary memory, so they can
stand up and be ready to use.
ROM is used in simpler electronic devices to store a firmware which runs a device when
the device is switched on, and there's some types of ROM, so you have p-rom, which stands
for a programable read-memory only, and it's different from true ROM, and that a ROM
is programmed, the data is written to it during the manufacturing process.
A p-rom is manufactured in empty state, and then programmed later on a p-rom program
or a burner.
Then you have an e-prom, and an e-prom stands for Erasable Programable Read-Only Memory.
As the name suggests, the data stored in an e-prom can be erased, and the e-prom can
be programmed again, or it's an e-prom involves removing it from the computer and exposing it
to ultraviolet light before re-burning it.
Then there is an e-e-prom, an e-e-p-rom, and it stands for Electrically Erasable Program
on Board Read-Only Memory, and the distinction between an e-p-rom and an e-e-p-rom is rather
it can be erased and written to by the computer system, and it's installed in, and that the
e-e-prom is not strictly read-only.
However, in many cases, the ride process is slow, so it's normally only done to update
program code, such as firmware BIOS code, on the occasional basis.
Confusionally, NAD Flash Memory, such as that found on USB sticks and solid state drives,
is a type of e-e-rom, but NAD Flash is considered to be secondary memory.
So secondary type memory types.
So we have hard disk, and we have SSDs, and we have optical, like a CD, or DVD drive,
we have tape drives.
Secondary memory also includes storage arrays, including 3D-NAD flash arrays connected
over a storage air network or sand.
Storage devices, which may be connected over a conventional network, are known as network
attached storage, or NASH, arguably cloud storage, can also be called secondary memory.
So the differences between RAM and ROM, a ROM is non-vautable, it's fast to read, it's
usually easily used in small quantities, it cannot be written too quickly, it's used
to store boot instructions or firmware, it's relatively expensive per megabyte stored
compared to RAM, and what is RAM, RAM is volatile, it's fast to read and write, it's
used as a primary system to store data, including program code, that the CPU needs to act as
immediately.
It's relatively cheap per megabyte compared to ROM, but it's relatively expensive compared
to secondary memory, so what technology is between primary and secondary memory?
In the last year or so, a new medium called 3DX point has been developed with characteristics
that lie between primary and secondary memory, a 3DX point is more expensive, but faster
than secondary memory, and it's lower cost, but slower than RAM, it's also a non-volatile
memory type, and these characteristics mean that it can be used as an alternative to RAM,
and systems which require vast amounts of system memory, that would be too expensive to build
using RAM, such as systems hosting in memory databases.
The trade-off is that such systems do not enjoy the full performance gains as you're
using RAM, since the 3DX point is non-volatile, systems use a 3DX point for system memory can
be up and running again after a power failure or interruption very quickly without the need
for all the data to be read back into system memory from the secondary memory, and I did
a show about PMM, and I think Intel's PMM technology came from this 3DX point.
Alright, hey, you all have a great time, I'll talk to you next time, enjoy your day.
to find out how easy it really is.
Hosting for HBR has been kindly provided by an onsthost.com, the Internet Archive and
R-Sync.net.
On the Sadois status, today's show is released under Creative Commons, Attribution 4.0 International
License.