Rightsizing

[fivemack]

I have a laptop fit for an itinerant computational mathematician; half a gigabyte of memory, P4/2800, three large fans.

I have now realised that I am not an itinerant computational mathematician, and, after looking around the sea of iBooks and Vaios at NotCon, have gone onto eBay and bought a second-hand Thinkpad 240. It's the kind of laptop I used to have, carried backwards and forwards to college for eighteen months in a standard A4 Jiffy bag; I wrote most of the text in my thesis on it. It weighs a third as much as my current laptop, and has a tenth the CPU power; that is, it'll be idle only 90% rather than 99% of the time.

It's, err, about the equivalent of downgrading from a Cray 2 to a Cray 1 in order to read email, IRC, and write Livejournal postings. Since these are tasks the equivalents of which our ancestors performed quite happily with a quill pen, and the new machine will still be more powerful than the systems on which the US's current nuclear arsenal was designed, I don't feel I'll be underpowered.

I'll put the big laptop on ebay when the small one arrives, and see if I was right to anticipate depreciation of 50% per year.

Comments

On that subject...

[tombee.livejournal.com]

Louisa and I were recently unsure as to whether a 1984-ish Cray 2 was actually more or less powerful than, say, a 2002 top of the range desktop PC. I reckon less. Are you a) able to advise, and b) ever so slightly scared by all this?

Re: On that subject...

[fivemack.livejournal.com]

I think the Cray 2 is a bit less powerful, though it depends somewhat on what sort of thing you're doing. If you're doing lots of random memory accesses, probably the Cray still wins.

Jack Dongarra at Tennessee has been benchmarking computers for longer than I've been alive; he has a two-processor Cray C90 (a much more modern machine than the Cray 2; I think dated around 1991) scoring 2.92GFLOPs and a single processor P4/2533 scoring 3.21.

A large Cray 2 had four processors, each running at 240MHz and performing two operations a cycle, and up to four gigabytes of memory, accessed at about 2 gigabytes per second.

The aggregate peak processing power is 2 gigaflops, which is less than the peak for any P4. The memory bandwidth is well below the peak on the P4, but I'm not sure the 2002 pentium-4 chipsets were adequate to get enough efficiency actually to beat the Cray. 4GB is still quite a lot of memory.

Re: On that subject...

[mobbsy.livejournal.com]

I'm often amused by the observation that for a sufficiently long calculation, the fastest way of getting an answer for a given budget is to wait n months before buying the hardware.

[dd-b.livejournal.com]

Laptops were one of the last things in computers to get there, but *good enough* is one of the most important milestones; specifically the point where down-market stuff is *good enough*.

There's a laptop I'm faunching after at the moment (but have no actual need for, and no money to buy just as a toy); it's a 12" display (and laptop form-factor), 2GHz AMD processor, 512MB ram, CD-RW/DVD drive, I think a 30GB disk. And at least last week I could have bought it new at a local store for $700. I think it's powerful enough and has enough RAM for photo work on the road, and the ability to write CDs means I would have a meaningful way to make relatively secure archive copies of photos I took away from home.