What causes Bad Sectors on Hard Disk Drives (HDD)?

There are 2 categories of reasons.

1. You (nothing personal)

If you jar or jolt or jerk or jiggle or strike or shake or bang your pc while it is accessing the disk, you can damage that tiny piece, and cause a bad sector. And your pc is pretty much always accessing the disk, so…

What’s happening is that inside the hard disk drive is a…disk, an actual platter that is spinning fast, really fast. The platter contains all the data. As the platter spins the “head” of the disk (that which reads and writes the disk) floats over the platter on a laminar cushion of air flow with literally a few nanometers of space between them.  That’s about 1 millionth of a millimeter. So, yeah, small.

For an analogy, it’s like a 747 flying 1/32nd of an inch off the ground.

Sudden motions of the disk (or the computer containing the disk) can cause the head to contact the platter and scratch it. Usually this only happens for a fraction of a second and damages just a tiny portion of the disk. Just a sector or few.

2. Entropy

The theory of entropy states that everything in the universe tends towards disorder (or decay).

This is happening right now on your hard drive as you read this 😉

The specific sources of this decay are:

• original manufacturing defects
• heat
• wear over time
• tiny, tiny specs of dust (that get by the filter)
• vibrations of the building containing the device
• electrical disturbances (from the power company, lightening)
• error in the logic hardware of the drive
• “overclocking”

References:

• http://forums.overclockers.com.au/showthread.php?t=153022
• http://www.tomshardware.com/forum/265043-32-reasons-sectors

A “Bad Sector” is a term for a broken piece of Hard Disk Drive (HDD)–a very small piece. There are millions of sectors on a hard drive. EG, standard sector size is 512 bytes (aka 512B). Consider a typical disk (in 2015) of 1TB in size, or 1,000,000,000,000 bytes (1 trillion bytes). Doing some math: there are 2 million sectors on a 1TB hard drive.

That means everything you store on there is broken up into pieces of 512. Have a 100MB video file? It is stored as 2000 pieces of 512B each.

Fortunately, when sectors go bad, two mechanisms exist to help you.

1. The hard disk drive itself detects many bad sectors and remaps them so that data is stored elsewhere, in good sectors. You may never notice these.
2. Windows Operating System detects bad sectors and marks them to avoid using them in the future. Windows Vista, 7, 8 (and presumably 10 and later) detect when a “chkdsk” is necessary and prompt you to run it at next boot. If not, you can run “chkdsk” yourself.

Note: when the OS detects hard disk errors, you should IMMEDIATELY MAKE A BACKUP. DO NOT PASS GO. DO NOT COLLECT $200.

Then, get a new hard drive.

Usually things will only get worse. In the upcoming months, even days, even hours.

Why do sectors go bad?

Reference: https://en.wikipedia.org/wiki/Disk_sector

Distance for 10Base-T, 100Base-T, 100Base-T are 100m = 328 feet,

However, that is 90m solid plus 5x2m stranded patch at each end.  If you’re all stranded, then you get “less”

Reference: Ethernet over twisted pair at Wikipedia

Jump right to Contenders for purchasing.

An SSD is a Solid State Disk Drive (also known as a Solid State Disk), a new kind of storage device that has entered the mainstream in 2014. The disk drives you’ve been used to all along are regular HDD’s. A regular HDD contains a round disk called a platter on which the bits of information are written. It contains a spindle that spins, or “drives”, the platter so that the “head” can read and write information from and to the platter as it spins underneath. It is a “Hard” Disk Drive (HDD) to differentiate it from “floppy” (or flexible) platters that were used in the past (ending in the 1990s).

A Solid State “Drive” doesnt “drive” anything, and doesnt contain a disk or platter. So it’s a misnomer. But since it is a replacement for a HDD it is known by the term Solid State “Drive”.

On the inside it is basically a large USB Drive, configured to work as an internal hard disk drive (HDD).

It’s a drop-in replacement for an internal hard drive. With some caveats which i’ll discuss.

It is a drop-in replacement for 2.5″ drives. SSDs tend to be sized the same as 2.5″ HDDs. Ie laptop hard drives. Also, they have a SATA port and interface, so they will plug into the current standard drive interface in nearly all PCs today. You might want v3 of SATA (SATA IIII aka SATA 6.0Gbits/s) to take advantage of the SSD’s additional bandwidth capabilities, but it will work with the previous STAT II installed in most PCs that are a few years old.

So, you can pull out your old drive, and plug in your SSD, and it will work.

Well, sorta.

3.5″ drives, or desktop drives

The first problem is if you have a desktop. SSDs are 2.5″ so they plug right into laptops. But most desktop drives are 3.5″. So you’ll need a physical adapter. The adapter is 3.5″ on the outside, and 2.5″ on the inside. You plug your 2.5″ drive (eg, your SSD) into the adapter (or screw the adapter onto your 2.5" drive), and then the adapter plugs into your desktop PC. Sometimes you need to get a special one from the PC maker.

Erase-before-Writing Requirement

The other 3 issues:

• wear leveling
• write amplification
• Partition Alignment

require some background info to be able to talk about them.

It’s all about how writes happen. Reads are easy and just work.

Here are some key facts to keep in mind, which are crucial to understanding what’s gonig on:

• Data is written 4KB at a time. These are typically called pages.
• An SSD can NOT overwrite data. It has to erase it first. So to write, it has to perform a sequence of:
  1. erase
  2. write
• Data is erased 256KB at a time.
• A brand new SSD is empty, ie fully erased.
• Most file systems (developed with HDDs in mind) when they delete files, they dont erase them. They just mark the spots as available for overwrite and leave the old data there. This is problematic for SSDs, cuz that old data DOES have to be erased. More below.

These facts mean you write 1 page at a time (4KB), but you erase 64 pages (256KB) at a time.

In the picture below, you write the blue block. But if you want to erase, you have to erase a BUNCH of adjacent 4KB blocks simultaneously.

https://en.wikipedia.org/wiki/File:NAND_Flash_Pages_and_Blocks.png

(Note that in the picture above, to save space, only 9 x 4KB pages are shown, but in reality there would be 64 x 4KB pages in each 256KB block.)

So, for a new SSD, everything is golden, and writes of only 4KB happen everywhere into free (erased) pages and we’re fine.

The problem comes when we run out of space and have to re-use some old pages.

The OS filesystem will do this. It will have some disk pages that contain data that it knows is from a file that has been deleted. It will instruct the disk (SSD in this case) to overwrite this space.

But the SSD can not simply overwrite, it has to erase first, then overwrite.

And to erase, it has to erase 256KB (64 pages). If ALL of those 64 pages are unused (aka stale), and the SSD knows it (the OS filesystem knows more than the SSD does), then it can simply erase all 64 pages. But more than likely, some of the 64 pages contain real data that must be preserved.

So…the SSD has to copy the good pages to a safe place, erase the whole 256KB block, copy back the good pages, then write the new page that was requested.

In reality, what the SSD really does is pick another entire 256KB block somewhere that’s entirely empty, and copy the good pages to it, re-map where those good pages data is, then write the new page that was requested, keeping in mind its new mapping.

Either way this process is SLOW and would essentially reverse all of the speed benefits of SSDs in the first place.

In the pic below, you see 4 pages (A-D) written.

Then 4 more pages are written (E-H).

Then the original 4 are “overwritten”, meaning the OS has written new versions (A’-D’), and told the SSD that A-D are invalid. So the SSD knows A-D are now unused.

Until an erase happens, the supposedly free pages A-D can not be used by the SSD. So to re-use A-D, the SSD has to copy the good pages (E-H and A’-D’) somewhere else first so it can erase the block:
(click to enlarge) https://en.wikipedia.org/wiki/File:Garbage_Collection.png

The other problem with this whole erase & write issue is that it causes extra writes (re-writing perfectly good data) to happen. These extra writes wear out the SSD faster. The extra writes are called “write amplification” (see below).

In fact without remediation an SSD would die in a month or 2. So all SSDs are remediated.

Write Amplification

Because of the erase-before-writing requirement (see above), there’s all kinds of re-writing of good data going on. This means, that if you measured the writes going into the SSD at its interface, you would measure a certain amount of writes, but if you looked at what was going on inside the SSD, you’d see a lot more writing going on.

More writes going on inside than the OS asked for is called write amplification.

Garbage Collection

It would be impractical for the SSD to wait for a write command from the OS and then do its erase-then-write. That would be too slow, and no one would buy SSDs. So, instead, SSDs go about doing proactive garbage collection. This is a process by which they move data around creating entire blocks which are all unused data. Then they can erase those blocks when the SSD is idle, and be ready for a speedy write when asked for by the OS.

They also re-map pages. That means the OS asked me, the SSD, to write data at A but i am going to put it at B, and remember the mapping from A to B, so that when the OS asks to read the data at A, i know where to get it.

That’s another way to keep a full set of 64 pages of good data in a block, and keep other blocks completely empty.

All good for speed, but all this proactive activity creates more re-writes of good data, and thus increases “write amplification”.

Reference: https://en.wikipedia.org/wiki/Write_amplification

Wear Leveling

So, another limitation of SSDs (they are not quite a silver bullet, not quite the best thing since sliced bread), is that a given bit of storage can only be re-written 1000 times, for a low end device. Up to 100k for a very hi-end (and expensive!) device. The amount of times you can write a cell is called “write endurance”.

You could easily exhaust that resource in a month of windows running on a drive. There’s lots of things that windows overwrites constantly.

So…

SSDs try to ensure that each bit is written the same number of times, or as close as they can get.

But, some data, like OS files, or maybe your pictures and videos, are written to the disk and just stay there, for YEARS. Unchanged. If SSD did nothing, those bits would have 1 write cycle, while other bits have 100s and 1000s and the drive would die.

So, SSDs move static data around, so it can write some of that rapidly changing data to the fresh bits.

But, these extra writes increase write amplification. In the end, however, it’s a net increase in life for the drive.

Reference: https://en.wikipedia.org/wiki/Wear_leveling

Partition Alignment

The OS tends to read and write X-size blocks. You really want those to be aligned to the natural alignment of the SSD.

If not, then the OS block will overlap TWO SSD blocks. So when the OS writes that block, you will have to write (and thus erase) TWO SSD blocks. that’s wasteful, so align your OS.

That means your partition has to be aligned. I’m not sure how to do this yet.

OverProvisioning

That’s when you say the drive has a certain size, say 500GB, but it really has more, say, 600GB, which would be an extra 20%. The SSD uses this space internally to perform writes with erase, and to do garbage collection, and to move around data proactively to evenly distribute wear (“wear leveling”).

SLC, MLC, TLC

SLC – Single Level Cell

Means 1 bit per cell.
The most expensive.
The most number of writes, 100,000 range, lifetime

MLC – Multi Level Cell

Means “multi” bits per cell, but in practice it is almost always 2.
Mid-priced.
Middle number of writes, 10,000 – 30,000, lifetime

Altho, http://www.tomshardware.com/reviews/600-pro-ssd-review,3498-4.html said the MLC’s will do only ~5,000 P/E cycles, and something called “eMLC” (“e” for enhanced, i would guess) could do ~25,000-30,000 P/E cycles.

TLC – Triple Level Cell

Means triple (3) bits per cell.
The least expensive.
The least number of writes, 1,000 – 3,000, lifetime

Altho, http://www.tomshardware.com/reviews/600-pro-ssd-review,3498-4.html said the MLC’s will do only ~5,000 P/E cycles, and something called “eMLC” (“e” for enhanced, i would guess) could do ~25,000-30,000 P/E cycles.

How to optimize

SSD Speed Tweks at speedguide.net <http://www.speedguide.net/articles/ssd-speed-tweaks-3319 >

SSD Optimization Guide from TheSSDReview.com <http://www.thessdreview.com/ssd-guides/optimization-guides/the-ssd-optimization-guide-ultimate-windows-8-edition/>

Contenders

v2

What’s wrong with your hard disk drive?

If it’s not fixable at home, and it’s probably not, i trust Disk Doctor enuf to try them.  See below.  But first, some background material.

An excellent introductory video on hard drives is “Hard Drive Click of Death Explanation and Live Demonstration” on youtube. (If that ever disappears, i have it saved locally.)
There are several possibilities of what’s wrong with your disk.
The main components of a hard drive are a pc board (In this case, “pc” means “printed circuit” as in “printed circuit board” rather than “Personal Computer” which is more common). The pc board (also called “pcb” for short) is the “brains” of the drive. This pc board is also the thing that talks to the rest of the computer.

The drive has platters, magnetic wonders which contain billions of bits information arranged in concentric circles. This platter spins at high speeds. 5400 rpms. 7200 rpms. even 10,000 rpms.

The drive also has a “head” which scans across the spinning platters and reads the bits of information. The head floats on a laminar sheet of air that’s billionths of an inch thick.  Ie, really, really tiny.

NOTE: If you ever hear new noises coming from your drive, BACKUP IMMEDIATELY.  It is going to fail soon.  You dont know who much time you have.

So what could be wrong?

1. The head that reads the platter might have physically broken.  This is the most common reason.  This results in a repetitive clicking sound.
2. The motor that spins the platters might have broken.  If you put your head close to the drive, you can hear the platters spin up to speed.  It sounds like a whirring sound which gets higher and higher pitched as the drive spin gains speed.  If you dont hear that, it could be the motor (or the pc board failing to give the motor the right instructions to spin up).
3. The pc board may have broken in various ways.  There’s a ROM chip on it that contains firmware and initialization data for this particular drive, including the map of bad sectors.
4. If you hear a clatter in your drive, it’s likely your platters are vibrating. Stop the drive and restart it. Tho sometimes this resolves itself harmlessly without restarting.  But it is time to BACK UP YOUR DATA if you hear this.  Trouble with the motor that spins the platters can also sound similar to clatter.  Also the bearings that ease the friction between the moving parts can wear and sound like grinding, which is also similar to a clatter.

How to fix these things at home.

1. There are two things you can do that require removing the pc board from the drive.  This one is is the easy one.  CAREFULY unscrew the screws (usually torx) that keep the green pc board fastened to the drive.  If your screw driver slips and you scratch the pc board you’ve probably ruined it.  The pc board is usually on the “bottom”.  CAREFULLY pull off the pc board.  There are several “contacts” small, usually oval, pads of metal that contact other parts of the drive.  The pads can be on the drive side or the pc board side.  Get a new pencil eraser, that’s clean.  Rub it on the contact pads to rub off corrosion.  Reassemble the pc boards.  This helps occasionally.
2. I have heard negative recommendations about putting your drive in the freezer.  It is said that if the drive has air exchange with the outside, condensation will form on the platter.  A water condensation droplet is ginormous compared to the head “fly height”.  But if the drive is sealed, then you’re safe, and you can take advantage of the different temperatures which can change the way the electronics work, and physically shrink the dimensions of components, and you might get lucky and it might work.  Unfortunately, I dont know how to tell if the drive is sealed.
3. Other than freezing, you can power up the drive, hold it in your hand, and spin it violently in a plane parallel with the platters. This might un-stick the motor or make the head pass a problematic spot.  DONT DROP THE DRIVE if you attempt this.
4. The other possibility is to buy an identical drive, and swap the pc boards. And when i say identical i mean really, really identical. The main part number, the sub-part number, all those funny character codes on the drive, front and back. And try to get drives that were made in the same month. So, as i said, really identical. I guess these drive manufacturers are always tweaking things. However, from what i hear (i have not personally confirmed) drives made in the last decade, ie most drives, have a ROM which stores parameters specifically tuned to this physical drive, ie compensating for any physical variances which have appeared on this particular unit. Including the map of bad sectors. So they say if you swap the pc board, you have to move the ROM from the old drive’s pc board to the new pc board. This involves heat to un-solder the two ROMs and heat to solder the old ROM into the new board.
   • (Calling it a ROM chip is a bit misleading, cuz ROM stands for Read-Only Memory, and this memory is written to, because the drive updates it. That means it’s programmable, or PROM.  However, since it’s programmable from the pc board it is likely an EEPROM, or Electrically Erasable Programmable Read-Only Memory chip.  Regardless….)
   • It’s also called a BIOS chip. How can you identify the HDD PCB’s BIOS?  All of the chips with 8 pins (4 pins on each sides) labeled 25P05VP、25P10VP、25F512、25F1024、25F1024AN、SST25VF512、SST25VF010, eg. are BIOS chips. There are not many 8-pin chips on the PCB, so they are easier to find than they could be.  [There may be other types of BIOS chips not listed here.]
   • If there is no 8-pin BIOS chip on the PCB, it is likely the BIOS is integrated on the Main Chip IC, or Controller. (“IC” stands for “Integrated Circuit”.) It is more complex to exchange the Main Chip IC than exchange the BIOS. If you plan to try this, it would be wise to attempt it several times on the PCB of a different HDD, one who’s data you can afford to lose.  Practice makes perfect.  But at this point you might want to hire a(n expensive) company.
   • I can not vouch for the videos below, but it found them interesting as background:
   • Why Control Board Swaps don’t work anymore   by Gillware Data Recovery    http://www.youtube.com/watch?v=ICR-xw1FYlU
   • DIY: Repair Hard Drive PCB. How to swap circuit board ROM chip.  by Donor Drives  http://www.youtube.com/watch?v=Yn2eL4o-6Eo

Disk Doctor    http://www.diskdoctors.com/

I called Disk Doctor 1.800.347.5377 and gave them the once-over.

They are expensive.  $450-$850 if it is NOT a mechanical problem.  $850-$1600 if it IS a mechanical problem.

It all hinges on: Do they have to open the drive and work on the motor, head or platters?  If so, they need to use their (expensive) clean room.  That costs big bucks.

If they only need to work on the pc board, then it’s cheaper.  Not cheap, but cheap-er.

They have a free diagnostic service.  Then they will tell you what price range you’re at.

And if you decide not to do it, you CAN get your hard drive back.  Perhaps to consider other options, or perhaps to wait until later when you can afford the fix.

But as far as i can tell from a phone call, they can be trusted.  I talked to a technician, twice.

He explained that the ROM BIOS chip contains the firmware, the map of bad sectors or blocks, and tuning data for the drive.

He explained that the first thing the drive does when it powers up is read a special sector to initialize itself.  That data must match what’s in the ROM.  If not, then the pc board never initializes.  And you can often hear a clicking sound.

The pc board both controls the reading off the platter, and also talks to the computer. It must be healthy and speaking the right language for the PC to recognize the drive.  But does the pc board need that first disk read before it can talk to the PC.  Yes, the tech assured me.

The tech confirmed that most of the time the problem is with the head.  That means opening the drive, using the clean room, and $$$$ 🙁

And he explained to me that they can measure various currents at the drive interface (without opening the drive, ie without incurring the clean room cost) and tell what is wrong with the drive.

I trust them enuf to give them a try.  If they can successfully restore a couple drives for me, i would trust them fully, but i havent gathered that data yet.

February 18, 2014

Here is an excellent answer to this question i found online.

http://forums.pcworld.com/index.php?/topic/33801-can-you-swap-the-main-hard-drive-from-one-computer-into-another-computer/

SigitNurhadi

Posted 19 June 2008 – 10:54 PM

If you remove a hard drive ( in this case, the boot drive that has the operating system, applications, and all the other stuff in it) from one computer and install it on another computer, will it work?

 

smax013

Posted 20 June 2008 – 02:36 AM

Yes, it CAN work…but may not or you might run into some challenges.

There are a few caveats, however. As first noted, you will have to deal with the driver issue. If the computer has different equipment (which is rather likely unless you talking about two identical computers such as maybe where one has a problem and the second is a replacement and you want to swap drives and then will send the other one back), then they will use different drivers. This can potentially result in a system crash (and maybe BSOD) upon boot-up in many cases as the drivers will be different enough. To deal with this, you should first uninstall ALL drivers on the system while the drive is in the old computer. Then shutdown (do NOT reboot as that will go through the process of trying to reinstall drivers). Then move the drive to the new computer and boot it up. It should then use the Windows Hardware Wizard to try to load as many drivers as it can. You might then have to locate some drivers that don’t come standard with Windows and install them “manually”.

The second caveat is activation. If the OS is one of Microsoft’s more modern OSs (i.e. Windows Vista or XP…and maybe even Windows 2000…don’t recall for sure on 2000), then it has an activation function/”feature”. Part of activation is that if Windows detects a significant change of hardware (which moving a drive from one computer to a new computer will DEFINITELY do), then it must be re-activated. Generally speaking, this is more of just a hassle/speedbump, but it can be a deal breaker. Technically, if the old computer has an OEM license for Windows, then I believe you are NOT permitted to move that OS to another computer per the EULA of Microsoft’s OEM OS license. Thus, you might have trouble activating it. If it is a retail or upgrade license, then you should not have any problems strickly(sic) speaking and it should be just a matter of jumping through the hoops (which might be as simple as doing it online, but could mean having to call Microsoft and telling what is going one to get it activated). If it is a volume/site license Windows install, then you should have zero trouble with activation…same with older Windows OS such as Windows 98, 98se, and Me.

The last caveat is a small one…drive connector compatibility…this all assumes that your new computer supports the type of hard drive that is in the older computer. If your old computer has an IDE drive and the new computer for some reason does NOT have any IDE connectors, then you might hit a road block (there are some adapters out there, but I have not always heard good things about them). The parallel issue is that if the old computer is old enough, then you might not be too keen on using an older (and potentially smaller) hard drive. Now, the way to pontential(sic) deal with both these items is to clone the drive to a brand spanking new hard drive (just make sure to uninstall the drivers BEFORE you clone it…and then use a bootable CD of the cloning software so that you don’t start up the driver reinstall process).

EDIT:

9/6/2015

I have performed this operation.

1.

I cloned (Using Macrium Reflect Technicians) a 4th-gen Intel Core-i5 HP ProDesk machine
and tried to boot into a 1st-gen Intel Core-i5 Intel board machine.

It didnt work, but i used Macrium Redeploy and then it DID work!

Well, it booted.

This was Windows 7.

So upon booting, it auto-installed like 12 dirvers for the new hardware.

2.

Then I tried the exact reverse direction
Disk from a 1st-gen Intel Core-i5 Intel board machine
to a 4th-gen Intel Core-i5 HP ProDesk machine.

Here Macrium Redeploy did not work.

But I WAS able to boot into safe mode with networking.

Windows 7 then proceeded to install a few drivers.
I kept rebooting into safe mode with networking.
It kept installing drivers.
Including chipset driver.
Until it was finished.

Still blue screen’ed when trying to boot into regular mode (not safe mode).
Error message was igdkmd64.sys;
Which i looked up–hd graphics.
Sure it’s the wrong one–these PCs are 3 generations apart. gen 1 and gen 4.
So in safe mode I uninstalled the graphics driver
And rebooted into safe mode.
It then automatically installed the right graphics (display) driver.
And then it booted in regular mode (not safe mode).
It then auto-installed better HID mouse and keyboard drivers.
And it was up and working.
yea.

Intel Matrix Storage Technology is a RAID system that uses firmware (bios) rather than hardware (on drives and/or on motherboard) or software (either within Windows or LInux, or in a driver or application program).

It has a disk-image like recovery feature:

Intel® Rapid Recover Technology (Intel® RRT): With the ability to instantly boot off a clone, Intel Rapid Recover Technology (part of Intel Matrix Storage Technology) provides a fast, easy-to-use method for the end user to recover their data and return their system to an operational status.

Whole Article: http://www.intel.com/design/chipsets/matrixstorage_sb.htm

Chips and modules

For use in Desktop computers, DDR, DDR2, DDR3 SDRAM is supplied in DIMMs (Dual Inline Memory Modules) with 240 pins and a single locating notch

Laptop DDR, DDR2, DDR3 SO-DIMMs, sometimes written without the dash: SODIMM, have 200 pins and often come identified by an additional S in their designation. The “SO” in SODIMM stands for “Small Outline”.

DIMMs are identified by their peak transfer capacity (often called bandwidth).

* Some manufacturers label their DDR2 modules as PC2-4300, PC2-5400 or PC2-8600 instead of the respective names suggested by JEDEC. At least one manufacturer has reported this reflects successful testing at a higher-than standard data rate^[4] whilst others simply round up for the name.

Note: DDR2-xxx denotes data transfer rate, and describes raw DDR chips, whereas PC2-xxxx denotes theoretical bandwidth (with the last two digits truncated), and is used to describe assembled DIMMs. Bandwidth is calculated by taking transfers per second and multiplying by eight. This is because DDR2 memory modules transfer data on a bus that is 64 data bits wide, and since a byte comprises 8 bits, this equates to 8 bytes of data per transfer.

To clarify 2 similar acronyms:

SRAM – Static RAM – this type of memory is used in various places in various chips in the PC (but not main memory, nor hard drisk drive main storage). It is used in caches and register files.

SDRAM – Synchronous Dynamic RAM – this is the type of memory people mean when they say “my pc has 4GB of memory” (4GB is typical in 2013).

Even tho they both start with ‘S’ one is Static and the other is not. In one case the ‘S’ means “Static” and in the other it means “Synchronous”.

Another memory term:

SODIMM – Small Outline DIMM. Ie laptop memory.

Also begins with ‘S’ but in this case the ‘S’ means “Small”.

2 other terms:

“Volatile” means memory that is lost when power is applied. Examples are the memory (not the hard disk drive) inside your computer.)

“Non-Volatile” means memory is still store when power is turned off. Examples are flash, as in usb drives. Eg usb drive retains its storage when unplugged.)

Reference: Random-access memory on Wikipedia