The ₹60,000 Lab Upgrade: RAM or SSD First?
Sunrise Public School, Cuttack, has a 25-seat computer lab. Twelve machines are eight years old: 4 GB RAM, a 500 GB 7200-rpm hard disk, and a 32-bit operating system. Teachers report that opening a browser and the C IDE together makes the systems nearly unusable: Task Manager shows 95–100% disk usage, memory around 3.2 GB of the 4 GB “usable”, and heavy page-file activity. The hard-disk activity light stays on almost continuously. The lab has ₹60,000 for upgrades. A vendor quotes ₹2,400 per PC for an 8 GB RAM kit and ₹3,000 per PC for a 256 GB SATA SSD; installing a 64-bit operating system is free. The teacher wants to buy RAM for all twelve PCs first. Before spending, the school asks you to justify the upgrade order and check whether the plan fits the budget.
1. Which component is the primary bottleneck, and why would adding the 8 GB RAM kit alone not deliver the expected improvement on these PCs? Use the symptoms and the 32-bit limit in your answer.
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Primary bottleneck: the disk, not RAM. The decisive symptom is 95–100% disk usage with continuous disk activity while memory is only about 3.2 GB used. Opening a browser and an IDE together exceeds the usable RAM, so the 32-bit OS pages memory to the 500 GB hard disk. The hard disk is roughly two orders of magnitude slower than RAM, so the machine spends most of its time waiting for page reads and writes; the CPU is mostly idle. Adding an 8 GB kit alone cannot help much because a 32-bit OS typically addresses only about 3.2–3.5 GB of RAM; the extra 4+ GB is not usable. A 32-bit address space has 2^32 bytes, i.e. 4 GB, and some of that is reserved for hardware and the OS. The free 64-bit OS must be installed first to make the RAM visible. Even then, an SSD would remove most of the page-file wait because random reads and writes are far faster. So RAM alone is the wrong first purchase: it neither fixes the paging latency nor is fully addressable.
2. Recommend a purchase and installation order for the 12 PCs within ₹60,000. Show the cost of each option and justify what you would defer.
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Costs for 12 PCs: RAM only = 12 × ₹2,400 = ₹28,800. SSD only = 12 × ₹3,000 = ₹36,000. Both = 12 × ₹5,400 = ₹64,800, which exceeds ₹60,000 by ₹4,800. Since the disk is the primary bottleneck, buy an SSD for all 12 first: ₹36,000. Install the free 64-bit OS on all 12 before or with the SSD. The remaining ₹24,000 buys 10 RAM kits (10 × ₹2,400). Put the 10 kits in the machines used for browser plus IDE; leave the two least-used machines at 4 GB until more funds arrive. This stays within budget and fixes the dominant symptom. Alternative: SSD for all plus RAM for all and request ₹4,800 extra; if allowed, that is better. Do not buy 12 RAM kits first: ₹28,800 leaves only ₹31,200, not enough for 12 SSDs, and the 32-bit limit would waste much of the new RAM.
3. Explain how virtual memory and page-file activity explain the near-freezing, and why an SSD changes the symptom even if RAM is unchanged.
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Virtual memory is disk space used as an extension of RAM. When the working set exceeds physical RAM, the OS moves pages out to the page file and reads them back on demand. If the disk is a slow 7200-rpm HDD, each page fault costs milliseconds; the system thrashes, and the user sees freezing even though the CPU is not overloaded. An SSD lowers page-fault latency dramatically because it has no seek time and much higher random IOPS. The symptom improves even if RAM is unchanged because the same number of page faults is serviced much faster. It is still better to add RAM as well: more RAM reduces the number of page faults, while the SSD makes the remaining faults cheaper. The two upgrades address different parts of the same problem.