Exhibit 99.1

Integrated Circuit Systems, Inc.

Corporate Headquarters

2435 Boulevard of the Generals

Norristown, PA 19403

Phone: 610-630-5300

Fax: 610-630-5399

Web Site: http://www.icst.com

Company Contact:

Justine Lien, CFO

Integrated Circuit Systems, Inc.

610-630-5300

INTEGRATED CIRCUIT SYSTEMS, INC. ANNOUNCES

FISCAL 2005 SECOND QUARTER RESULTS

Norristown, PA –January 21, 2005 – Integrated Circuit Systems, Inc. (NASDAQ: ICST) today announced financial results for the second quarter of fiscal 2005, ending on January 1, 2005.

($ millions, except EPS)	Q2FY 2005		Q2FY 2004		Y-Y Growth		Q1FY 2005		Q-Q Growth
Revenue	$	60.6	$	69.6	-12.9	%	$	66.1	-8.3	%
Gross Margin	$	35.4	$	41.5	-14.7	%	$	39.3	-9.9	%
Operating Income	$	15.3	$	21.8	-29.8	%	$	11.1	37.8	%
Net Income	$	14.0	$	18.7	-25.1	%	$	10.1	38.6	%
Diluted EPS	$	0.20	$	0.26	-23.1	%	$	0.14	42.9	%
Pro Forma Operating Income (1)	$	15.3	$	21.8	-29.8	%	$	18.1	-15.5	%
Pro Forma Net Income (1)	$	14.0	$	18.7	-25.1	%	$	17.2	-18.6	%
Pro Forma Diluted EPS (1)	$	0.20	$	0.26	-23.1	%	$	0.24	-16.7	%

(1) Pro forma operating income, net income, and diluted EPS is derived by removing research and development expense related to the asset acquisition which occurred in the first quarter of fiscal 2005.

Revenue declined 8% from the September quarter to the December quarter representing weak market conditions in digital consumer and communications. PC revenue grew 4% quarter-on-quarter as seasonally expected. Reflecting such product mix, gross margin compressed to 58.3% for the December quarter. During the previous quarter the Company took a charge of $7.1 million for the acquisition of research and development relating to the Video business unit. This charge is the largest component drop in operating expenses from the previous quarter. Operating expenses were cut during the quarter to reflect the downturn in business. Net income for the quarter on a GAAP basis is $14.0 million or $0.20 earnings per share, compared to $0.14 in the preceding quarter.

Revenues	Q2FY2005 % of Revenue		Q2FY2004 % of Revenue		Y-Y Growth		Q1FY2005 % of Revenue		Q-Q Growth
PC	48	%	46	%	-8	%	43	%	4	%
Digital Consumer	16	%	13	%	3	%	17	%	-12	%
Communications	30	%	32	%	-19	%	34	%	-21	%
Military	6	%	9	%	-40	%	6	%	-8	%

While we continued to invest in R&D spending during the December quarter, we took steps to control operating expenses through headcount reductions and by reducing manufacturing capacity in the Military business.

Also during the quarter we repurchased 287,500 shares and we plan on continuing our stock buyback program this current quarter.

Hock Tan, President and CEO, stated, “We believe that the weaknesses in Digital Consumer and Communications during the December quarter reflect temporary demand pullback, because inventories are being consumed in the pipeline. Once this is over, we continue to have confidence in the strong growth potential of our end markets.”

Second Quarter Fiscal 2005 Conference Call

ICS will host a conference call to discuss the earnings results for the second quarter of fiscal year 2005 at 9:30 AM eastern time January 21, 2005. The company will also discuss its strategic direction and market conditions. Interested parties are invited to listen to the conference call by dialing (877) 405-3430, or (706) 634-6397 for international callers; the conference ID is 2985136. The call will also be broadcast via the internet and can be accessed from ICS’ corporate website at www.icst.com.

About ICS

Integrated Circuit Systems, Inc. is a leader in the design, development and marketing of silicon timing devices for communications, networking, computing and digital multimedia applications. The Company is headquartered in Norristown, PA, with key facilities in San Jose, CA; Tempe, AZ; Worcester, MA and Singapore.

Statements included in this release, to the extent they are forward looking, involve a number of risks and uncertainties related to competitive factors, technological developments and market demand. Further information on these and other potential factors that could affect the Company’s financial results can be found in the Company’s Form 10-K filed on September 16, 2004.

INTEGRATED CIRCUIT SYSTEMS, INC.

CONSOLIDATED OPERATING RESULTS

	Unaudited Three Months Ended						Unaudited Six Months Ended
(In thousands)	Jan. 1, 2005		Oct. 2, 2004		Dec. 27, 2003		Jan. 1, 2005		Dec. 27, 2003
Revenues	$	60,628	$	66,096	$	69,565	$	126,724	$	134,850
Cost of sales		25,269		26,772		28,107		52,041		54,543
Gross margin		35,359		39,324		41,458		74,683		80,307
Expenses:
Research and development		9,426		10,187		10,014		19,613		19,322
Research and development Video acquisition		—		7,051		—		7,051		—
Selling, general and administrative		9,440		10,030		8,819		19,470		17,790
Deferred compensation		60		40		244		100		488
Amortization of intangibles		1,114		935		575		2,049		1,150
		20,040		28,243		19,652		48,283		38,750
Operating income		15,319		11,081		21,806		26,400		41,557
Other income (expense)		873		666		379		1,539		1,124
Income before income taxes		16,192		11,747		22,185		27,939		42,681
Income taxes		2,212		1,598		3,533		3,810		6,748
Net income	$	13,980	$	10,149	$	18,652	$	24,129	$	35,933
Basic EPS:
Net income	$	0.20	$	0.14	$	0.26	$	0.34	$	0.51
Diluted EPS:
Net income	$	0.20	$	0.14	$	0.26	$	0.34	$	0.49
Weighted Shares:
Basic		70,348		70,263		70,422		70,306		70,437
Diluted		71,468		71,373		72,882		71,421		73,087
Capital expenditures	$	2,557	$	2,736	$	2,295	$	5,293	$	4,458
Depreciation and amortization	$	2,923	$	2,623	$	2,192	$	5,546	$	4,297

Prepared in accordance with GAAP

INTEGRATED CIRCUIT SYSTEMS, INC.

PRO FORMA CONSOLIDATED OPERATING RESULTS

	Unaudited Three Months Ended						Unaudited Six Months Ended
(In thousands)	Jan. 1, 2005		Oct. 2, 2004		Dec. 27, 2003		Jan. 1, 2005		Dec. 27, 2003
Revenues	$	60,628	$	66,096	$	69,565	$	126,724	$	134,850
Cost of sales		25,269		26,772		28,107		52,041		54,543
Gross margin		35,359		39,324		41,458		74,683		80,307
Expenses:
Research and development		9,426		10,187		10,014		19,613		19,322
Selling, general and administrative		9,440		10,030		8,819		19,470		17,790
Deferred compensation		60		40		244		100		488
Amortization of intangibles		1,114		935		575		2,049		1,150
		20,040		21,192		19,652		41,232		38,750
Operating income		15,319		18,132		21,806		33,451		41,557
Other income (expense)		873		666		379		1,539		1,124
Income before income taxes		16,192		18,798		22,185		34,990		42,681
Income taxes		2,212		1,598		3,533		3,810		6,748
Pro forma net income	$	13,980	$	17,200	$	18,652	$	31,180	$	35,933
Basic EPS:
Pro forma Net income	$	0.20	$	0.24	$	0.26	$	0.44	$	0.51
Diluted EPS:
Pro forma Net income	$	0.20	$	0.24	$	0.26	$	0.44	$	0.49
Weighted Shares:
Basic		70,348		70,263		70,422		70,306		70,437
Diluted		71,468		71,373		72,882		71,421		73,087

INTEGRATED CIRCUIT SYSTEMS, INC.

PRO FORMA CONSOLIDATED OPERATING RESULTS

(continued)

	Unaudited Three Months Ended						Unaudited Six Months Ended
(In thousands)	Jan. 1, 2005		Oct. 2, 2004		Dec. 27, 2003		Jan. 1, 2005		Dec. 27, 2003
Reconciliation of our GAAP Net Income to our Pro Forma Net Income:
GAAP Net Income	$	13,980	$	10,149	$	18,652	$	24,129	$	35,933
Adjustments to Net Income:
Research and development Video acquisition				7,051				7,051
Pro forma net income	$	13,980	$	17,200	$	18,652	$	31,180	$	35,933
Reconciliation of our GAAP Operating Income to our Pro Forma Operating Income:
GAAP Operating Income	$	15,319	$	11,081	$	21,806	$	26,400	$	41,557
Adjustments to Operating Income:
Research and development Video acquisition				7,051				7,051
Pro forma operating income	$	15,319	$	18,132	$	21,806	$	33,451	$	41,557
Reconciliation of our GAAP Basic Net Income per share to our Pro Forma Net Income per share:
GAAP Basic Net Income per share	$	0.20	$	0.14	$	0.26	$	0.34	$	0.51
Adjustments to Basic Net Income per share:
Research and development Video acquisition				0.10				0.10
Pro forma basic net income per share	$	0.20	$	0.24	$	0.26	$	0.44	$	0.51
Reconciliation of our GAAP Diluted Net Income per share to our Pro Forma Diluted Net Income per share:
GAAP Diluted Net Income per share	$	0.20	$	0.14	$	0.26	$	0.34	$	0.49
Adjustments to Diluted Net Income per share:
Research and development Video acquisition				0.10				0.10
Pro forma diluted net income per share	$	0.20	$	0.24	$	0.26	$	0.44	$	0.49

To supplement the consolidated financial results prepared under generally accepted accounting principles (“GAAP”), ICS uses a non-GAAP conforming, or pro forma, measure of net income that is GAAP net income adjusted to exclude certain costs, expenses and gains. Pro forma net income gives an indication of ICS’s baseline performance before gains, losses or other charges that are considered by management to be outside of the company’s core operating results. In addition, pro forma net income (loss) is among the primary indicators management uses as a basis for planning and forecasting future periods. ICS computes pro forma net income (loss) by adjusting GAAP net income (loss) with the impact of non-recurring acquisition-related charges. ICS provides pro forma results as additional information for its operating results. These measures are not in accordance with, or an alternative for, generally accepted accounting principles and may be different from pro forma measures used by other companies.

INTEGRATED CIRCUIT SYSTEMS, INC.

CONDENSED CONSOLIDATED BALANCE SHEET

(in thousands, excluding Other Financial Data)	January 1, 2005			October 2, 2004			July 3, 2004
	(unaudited)			(unaudited)
ASSETS
Current Assets:
Cash and marketable securities	$	192,753		$	179,767		$	195,579
Accounts receivable, net		46,934			50,367			45,717
Inventory, net		20,880			21,446			18,772
Deferred income taxes		19,738			22,759			22,759
Other current assets		4,180			5,016			7,189
Total current assets		284,485			279,355			290,016
Property & equipment, net		21,096			20,364			19,254
Long term investments		5,000			5,000			5,000
Intangibles		43,187			44,307			27,842
Goodwill		35,422			35,422			35,422
Prepaid long-term maintenance contracts		4,400			4,781			—
Other assets, net		52			57			62
Total assets	$	393,642		$	389,286		$	377,596
LIABILITIES AND SHAREHOLDERS’ EQUITY
Current Liabilities:
Lease payable	$	73		$	119		$	82
Accounts payable		15,559			18,012			17,557
Accrued expenses and other current liabilities		5,260			7,348			8,518
Income taxes payable		1,946			4,193			3,576
Total current liabilities		22,838			29,672			29,733
Other long term liabilities		11,846			11,733			11,638
Total liabilities		34,684			41,405			41,371
Shareholders’ Equity:
Common stock		731			728			727
Additional paid in capital		288,207			284,996			282,569
Retained earnings		131,269			117,289			107,140
Deferred compensation		(861	)		(921	)		—
Treasury stock		(60,388	)		(54,211	)		(54,211	)
Total shareholders’ equity		358,958			347,881			336,225
Total liabilities and shareholder’s equity	$	393,642		$	389,286		$	377,596
OTHER FINANCIAL DATA:
Days sales outstanding		72			65			58
Inventory turns		4.1			4.8			5.2