Computer metrics

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I created this page for myself to help try and memorize and keep up with the changing "metrics" of computer in terms of the cost, performance and capacity of various computer components one might purchase. These metrics can help with back-of-the-envelope calculations, but they also change rapidly over time, hence I'll try and keep a timestamp on the values.

The Costs, Speed and Capacity of a Desktop Computer


The table below shows the approximate cost, speed and capacity of various computer/network components, as of mid 2012.

Component Performance Cost (gives example)
Processor (CPU) Individual cores can run as high as ~3.6GHz (.63 billion ops/sec), but most CPUs now have quad cores, so a slightly better benchmark is floating point operations per second (FLOPS). A modern desktop can run ~7-10 GFLOPs. L1 (~32kB/core) and L2 cache (256kB/core) are a fairly fixed size (hasn't varied much over time), but can now have up to 10 MB L3 cache per CPU (over all cores). Intel CORE i7 3820/3.6GHz/10MB CACHE/LGA2011/4CORES = $300 * *
Graphical Processing Unit (GPU) Single GPU can be 300 GFLOPs or more but best suited for matrix multiplication. nVidia XFX GeForce 8800 GS Graphics card/384 MB/DDR3 SDRAM = $180 *
Hard Disk Drive (HDD) 2 TB 7200 rpm... seek time = ~12ms, rotational latency = ~4ms... "disk-to-buffer" data transfer = 3Gbits/s WD RE4 2 TB/300 MBps/7200 rpm = $200 *
Solid State Drive (SDD) 256 GB and doesn't need seek time so are usually ~3x faster at data transfer than HDD Corsair Force Series 3 240 GB/600 MBps = $220 *
Memory (RAM) Most motherboards support up to 32 GB (4 x 8GB), but are now 16GB sicks and some motherboards have 8 slots, so potentially 64 or 128 GB $60 Corsair 16 GB:2 x 8 GB/DIMM 240-pin/1600MHz *
Ethernet 1 Gbits/sec "gigabit ethernet (GbE)" can be category 5-7 unshielded twisted pair (UTP) over short distance (<100 m) or fiber optic cable over longer distances (70 km) according to the gigabit ethernet specs spool of: fiber = $50/1000ft *, cat 6 = $120/1000ft *... most GbE switches are ~$100-200, but is $1000+ for a GbE router with fiber channels.

Clusters and Parallel Computing

Computer clusters for processing and storage can cost millions (depending on how many thousands of machines), but are useful at storage of huge amount of data (many petabytes) at executing parallel computing. If an problem can be solved using parallelization (running different/independent parts of the problem on many CPU cores at once), then they can be solved quickly using high performing computing (HPC) clusters or "supercomputers".

Each time an algorithm goes to the "next level", (L1 to L2 to L3 then memory, then perhaps disk) it slows down considerably. If time is important to solve a (parallelizable) problem, then the best options are:

Best Options by Speed Approx Capacity
(1) All in ram with single expensive high-performance machine Let's say 32 GB - 64 GB RAM, depending on how new/costly machine is
(2) Cluster of cheaper machines connected by gigabit ethernet 32 GB RAM per machines.
(3) Single machine with SSD "secondary storage" for memory paging 256 GB per SSD.... or many TB if HDD (but HDD 3x slower)

See Also