The ''silicon belt'' is bulging. High-technology firms are spilling beyond the Route 128 girdle and spreading west to Route 495. And this expansion is profoundly affecting the housing market in suburbs west of Boston.
''The impact has been phenomenal,'' says Craig Foster of Foster & Foster Realty, which has 20 offices in the area.
Low-slung brick office buildings and new homes now squat where Herefords grazed a decade ago. The setting remains rustic but housing costs have spiraled.
In the mid '70s, new growth was absorbed by towns west of Route 128 - Concord , Bedford, Acton, Chelmsford, and Sudbury. But by 1978, ''there were incredible price increases. High-tech demand grew and pressure increased for local communities to restrict growth,'' Mr. Foster explains.
Frustrated by zoning roadblocks and higher land costs, residential and commercial developers are now taking up positions along the periphery of Route 495 and pumping up prices there.
''A year ago, if you told me you were building a $100,000 or $105,000 home in Hudson or Marlborough, I'd say, 'You're nuts.' Not today,'' Foster says.
Why? Aside from the new companies flocking to these towns, nearby Westborough was selected recently to host the highly prized Microelectronics Center. Many consider this $40 million research and training facility a magnet for development. Wang and Data General have already bought land close by, says Ken Dallamora of Dallamora Real Estate in Framingham.
Still, it is near this second ''silicon belt'' along Route 495 that first-time buyers are told to hunt for their American Dream.
For properties of less than $100,000, Foster recomends Marlborough, Hudson, and Tewksbury, as well as parts of Chelmsford, Littleton, and Lowell. Closer to Boston, other Realtors add Billerica and Wilmington into the ''easily affordable'' list.
''Billerica is one of the few towns that has built a lot of homes in the last 10 years. And it's one of the most active markets in the state,'' claims Vincent DeLuca of Suburban Realty Group in Burlington.
Homes in Billerica average $95,000, he says. That same three-bedroom house in Billerica would sell for $110,000 in Burlington, $125,000 in Bedford, and $150, 000 in Lexington or Winchester, he adds.
Even nearer to Boston the lots are smaller and the houses older, but Woburn, Waltham, and Watertown do have some low-priced properties.
''In Watertown, single-family homes average $95,000,'' says Charles Agrillo of Century 21 West Realty. How many homes does he have at that price? ''None, right now.''
However, there is an abundance of two-family dwellings here, averaging $130, 000. And if someone rents one floor, Mr. Agrillo calculates, the monthly payments could be $300 less than payments on a $95,000 single-family home.
Next door, in Waltham, Paul McNulty of Coleman & Sons says there are a few properties for less than $100,000, but the bulk of homes are between $100,000 and $125,000.
If these prices seem high, brokers suggest: ''Go condo.'' Condominiums are becoming more popular as a way to build equity before moving up in the market. Realtors say Marlborough, Acton, Arlington, and Framingham are stocked with condos ranging from $50,000 to $90,000.
Moving up the ladder, to the under $125,000 rung, Realtors take buyers to Burlington, Arlington, Natick, and some parts of Bedford and Framingham.
On the next step are towns preferred by executive transferees - the $115,000 to $175,000 market in Framingham, Bedford, Newton, Needham, Winchester, Lexington, Belmont, Concord, Acton, Sudbury, Southboro, and Wellesley.
On the top rung: Lincoln, Carlisle, Weston, Dover, and Sherborn. Here the setting is serenely rural. Pre-Revolutionary stone walls flank lush meadows and oak-thick forests, which are often set aside as conservation land. Typically, lots are larger than an acre and neighbors are a wooded-walk away.
Prices climb into the ''upper 100s ($100,000) before you find anything interesting,'' says Marge Smith of Borroughs-Smith Realtors in Lincoln. Most homes fall into the $200,000 to $400,000 range and new building starts at $250, 000, she says.
Throughout the western suburbs, school systems are consistently praised and transportation, a nicely meshed web of major roads and two rail links to the city, is lauded.
The current seller's market has seen tremendous increases of 15 to 25 percent as buyers outbid each other for a diminishing supply of homes.
But in recent weeks, the buying has abated. Craig Foster explains: ''As interest rates started up in April and May, it increased activity as buyers were anxious to close. Then, as the rates crest and soften, that slows the market down because people feel they can wait now until it drops (further).'' But, with interest on a fixed-rate, 30-year mortgage at 14 to 15 percent, ''we've clipped the wings of first-time buyers now.''