5 ms·

This is not random access; the latency depends on the position of the read/write head over the spinning platter. Other analogies may be more apt. Also I guess

This is not random access; the latency depends on the position of the read/write head over the spinning platter. Other analogies may be more apt. Also I guess they could have just as well built that with a Pick and Place machine out of an electronics manufacturing company, but I guess UdK has an emphasis on things being hand-made and looking artsy.

Paul_S 9y ago
Modern RAM access time is not deterministic either. Certainly not on the modern desktop.
TheSpiceIsLife 9y ago
It is random access because the device doesn't have to touch every grain of sand on the way to the one it intends to deal with next. It's very similar to a spinning-platter hard drive: latency depends on rotational velocity of the platter and radial velocity of the read/write head. That the latency is quite high in this device doesn't make it any less random-access.
- lanna 9y ago
  > It is random access because the device doesn't have to touch every grain of sand on the way to the one it intends to deal with next. what you described is called "sequential access" > It's very similar to a spinning-platter hard drive: latency depends on rotational velocity of the platter and radial velocity of the read/write head. hard drives & etc. are called "direct access" > That the latency is quite high in this device doesn't make it any less random-access. the problem is not that the latency is high but that the latency varies. from wikipedia: "A random-access memory device allows data items to be read or written in almost the same amount of time irrespective of the physical location of data inside the memory. In contrast, with other direct-access data storage media such as hard disks, CD-RWs, DVD-RWs and the older drum memory, the time required to read and write data items varies significantly depending on their physical locations on the recording medium, due to mechanical limitations such as media rotation speeds and arm movement." https://en.wikipedia.org/wiki/Random-access_memory https://en.wikipedia.org/wiki/Random-access_memory
  - dfox 9y ago
    On the other hand, latency of DRAM also depends on the physical location of data accessed (precharge, bank selection...). But for DRAM case it only depends on sequence of previous operations and does not change with wall time, for direct-access media it changes with time.
- dfox 9y ago
  I fact hard drives and similar rotating disc media are not random-access according to your otherwise reasonable definition. Modern (ie. anything that was ever intended for personal computers and probably every harddrive ever sold by IBM as "DASD") hard drive does not known where given sector is physically located on the platter and does not care what is the current angular position of the heads. Instead it seeks to correct track and reads whatever data is there until it gets to sector header with correct sector address and then either reads or overwrites the sector (ie. it does have to touch irrelevant data).
  - benchaney 9y ago
    > I fact hard drives and similar rotating disc media are not random-access according to your otherwise reasonable definition. I don't see that as an issue with GP's definition. Hard drives aren't random access.
- benchaney 9y ago
  > It is random access because the device doesn't have to touch every grain of sand on the way to the one it intends to deal with next. This isn't what random access means. "In computer science, random access (more precisely and more generally called direct access) is the ability to access any item of data from a population of addressable elements roughly as easily and efficiently as any other, no matter how many elements may be in the set. It is typically contrasted to sequential access." https://en.m.wikipedia.org/wiki/Random_access https://en.m.wikipedia.org/wiki/Random_access
heavenlyblue 9y ago
This project doesn't just look "artsy" - it is an art project in the first place. While you could go on about the technicalities of what kind of memory is being represented here, IMO the main reason they called it "RAM" is because it's a term that is known to a layperson; so it immediately rings a bell.
dTal 9y ago
Never mind, just put a small, variable delay after each operation to make it constant time. Or a large, fixed delay - that way the jitter will be a small proportion of the total access cost. That should make it random access.

Paul_S 9y ago

Modern RAM access time is not deterministic either. Certainly not on the modern desktop.

TheSpiceIsLife 9y ago

It is random access because the device doesn't have to touch every grain of sand on the way to the one it intends to deal with next. It's very similar to a spinning-platter hard drive: latency depends on rotational velocity of the platter and radial velocity of the read/write head. That the latency is quite high in this device doesn't make it any less random-access.

lanna 9y ago
> It is random access because the device doesn't have to touch every grain of sand on the way to the one it intends to deal with next. what you described is called "sequential access" > It's very similar to a spinning-platter hard drive: latency depends on rotational velocity of the platter and radial velocity of the read/write head. hard drives & etc. are called "direct access" > That the latency is quite high in this device doesn't make it any less random-access. the problem is not that the latency is high but that the latency varies. from wikipedia: "A random-access memory device allows data items to be read or written in almost the same amount of time irrespective of the physical location of data inside the memory. In contrast, with other direct-access data storage media such as hard disks, CD-RWs, DVD-RWs and the older drum memory, the time required to read and write data items varies significantly depending on their physical locations on the recording medium, due to mechanical limitations such as media rotation speeds and arm movement." https://en.wikipedia.org/wiki/Random-access_memory https://en.wikipedia.org/wiki/Random-access_memory
- dfox 9y ago
  On the other hand, latency of DRAM also depends on the physical location of data accessed (precharge, bank selection...). But for DRAM case it only depends on sequence of previous operations and does not change with wall time, for direct-access media it changes with time.
dfox 9y ago
I fact hard drives and similar rotating disc media are not random-access according to your otherwise reasonable definition. Modern (ie. anything that was ever intended for personal computers and probably every harddrive ever sold by IBM as "DASD") hard drive does not known where given sector is physically located on the platter and does not care what is the current angular position of the heads. Instead it seeks to correct track and reads whatever data is there until it gets to sector header with correct sector address and then either reads or overwrites the sector (ie. it does have to touch irrelevant data).
- benchaney 9y ago
  > I fact hard drives and similar rotating disc media are not random-access according to your otherwise reasonable definition. I don't see that as an issue with GP's definition. Hard drives aren't random access.
benchaney 9y ago
> It is random access because the device doesn't have to touch every grain of sand on the way to the one it intends to deal with next. This isn't what random access means. "In computer science, random access (more precisely and more generally called direct access) is the ability to access any item of data from a population of addressable elements roughly as easily and efficiently as any other, no matter how many elements may be in the set. It is typically contrasted to sequential access." https://en.m.wikipedia.org/wiki/Random_access https://en.m.wikipedia.org/wiki/Random_access

heavenlyblue 9y ago

This project doesn't just look "artsy" - it is an art project in the first place. While you could go on about the technicalities of what kind of memory is being represented here, IMO the main reason they called it "RAM" is because it's a term that is known to a layperson; so it immediately rings a bell.

dTal 9y ago

Never mind, just put a small, variable delay after each operation to make it constant time. Or a large, fixed delay - that way the jitter will be a small proportion of the total access cost. That should make it random access.