How much memory does a Ghost take up?
 

On the internet, I've seen estimates of a full brain map being anywhere from a petabyte to a zettabyte*, so what estimates are given either by canon THS or your version of the setting?

*The zettabyte is based off of a mouse brain map (being a millionth of a human brain in volume) requiring about a petabyte of storage space.

Re: How much memory does a Ghost take up?
 

Pre-Transhuman Space, SJGames began by side-stepping the issue. Pre-Gurps (all the way back in Car Wars) you read your memories directly into your clone in storage.

A TL after that there was a bulky and just barely portable thing called a "Mechanical Memory Storage Device" or MMSD. Its' capacity was unspecified.

After that you put "brain tapes" (yes, the concept does go back to tape drives) on standard computer media. I don't quite remember the first capacity figure given for such media but I'm pretty sure it was laughably low. Possibly even in GB.

By late 3e the number had crept up to 100 TB.

The number that came up when I was searching during the TS playtests was 100x that or 10,000 TB. some people wanted to keep the 100 TB arguing that it represented data compression.

I don't honestly remember what went into the printed version. I had lost faith in the basic concept by then anyway.

By all means, use the number that looks best to you. You need to keep the concept out of the "retrotech" ghetto. :)

Re: How much memory does a Ghost take up?
 

When I was researching GURPS High-Tech: Electricity and Electronics, I found that in 2007, a Swiss research institute had simulated one cortical column of a rat brain on an IBM Blue Gene/L supercomputer. Human cortical columns are estimated to be six times as sophisticated as rat cortical columns, and a human brain has a million of them. That suggests that you might need 10^7 supercomputers to run a true ghost program. I might go with that as an estimate.

Re: How much memory does a Ghost take up?
 

Probably not; a full simulation is almost certainly doing a lot of things it doesn't really need to do, but our understanding of neurons isn't sufficient to know exactly what those things are. A ghost presumably has to keep state information of around a hundred billion neurons plus a similar number of glial cells, but how much state information is actually needed per cell is not clear. One terabyte is almost certainly optimistic, but one hundred terabytes (a few hundred bytes per cell) is certainly believable as a count of the actually necessary information.

The problem for ghosts is that distinguishing which information you actually need is not trivial; you could certainly wind up with a megabyte per cell when doing a naive brain peel.

Re: How much memory does a Ghost take up?
 

Keep in mind that the static 'map' will also need processor capacity and more memory to actually do anything. And nobody has the slightest idea how much.

Re: How much memory does a Ghost take up?
 

Ghosts are all Complexity 7 (Changing Times, p. 53), which means as data they take up 10TB (Transhuman Space, p. 143). One advantage of a ghost over an SAI is that Ghosts are smaller than SAIs of IQ10 or more.