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Legacy Products
386-to-486 Upgrade Processor FAQs

NOTE: The information provided below is for a Cyrix product that is no longer in production.

Q. Is the Cyrix 386-to-486 Upgrade processor still available?
A. No. The Cyrix 386-to-486 upgrade processors are no longer in production or sold by Cyrix.

Q. Which 386 systems can use the Cyrix Upgrade?
A. Cyrix makes upgrades for 386SX systems from 16 MHz to 25 MHz and 386DX systems from 16 MHz to 33 MHz. Cyrix does not make an upgrade for 386DX 40 or 386SX 33 or 40 MHz computers.

Q. Will it work in my system?
A. Cyrix Upgrades are generally compatible with all 386 PCs. Remember we cannot upgrade 386SX-33MHz or 40MHz PCs nor can we upgrade 386DX-40MHz computers. You also can download and use the free Cyrix Upgrade Verification Program Software, which determines the upgradeability of all 386 PCs.

Q. Which one of the Cyrix Upgrade products do I use?
A. If you have a 386SX PC, use the CX-486SRX2-25/60. If you have a 386DX PC, use the CX-486DRX2.

Q. Will the Cyrix Upgrade work with my existing math coprocessor?
A. There may be a problem with an older 387 and the Cyrix Upgrade. Typically these parts have a slow response time that cause the system to stall. A new Cyrix math coprocessor solves this issue.

Q. Does the Cyrix Upgrade have a Math Coprocessor built in?
A. No. Using a single chip design, there was not enough room to incorporate this device. Further, your system anticipates an external 387 and is "timed" for an external rather than an internal math coprocessor.

Q. Will the Cyrix Upgrade turn my 386 into a 486?
A. Yes. Your computer will now be able to execute all 486 instructions, which it could not do as a 386.

Q. What kind of performance improvement can I expect?
A. CPU benchmark programs such as Landmark or Norton SysInfo will show anywhere from 300 to 500 percent improvement. This, of course, is simple CPU performance. Application benchmarks such as PC Bench, SysMark, and others will show about a 100% increase, which is more indicative of real-world performance.

Q. How long will it take to install the Cyrix Upgrade processor?
A. A typical installation will take 15 minutes or less. Exceptions occur when you do not have easy access to your 386 processor or some troubleshooting is needed to make the Upgrade work correctly.

Q. What comes with the Cyrix 386-to-486 Upgrade?
1. The Upgrade microprocessor.
2. Cache Software utility diskette (5 1/4" and 3 1/2").
3. User's Manual.
4. Removal tools (386DX Upgrade only).
5. A bright orange arrow (for pointing out pin one on your 386 processor).
6. Warranty/registration Card.
7. Heatsink.

Q. What is the cache utility diskette used for?
A. This diskette contains the utility that actually enables or "turns on" the 1K internal cache in the Cyrix Upgrade. There are simple installation procedures to accomplish this if you're running DOS/Windows, OS/2, or Windows NT.

Q. Do I just remove my 386 processor and put the Cyrix Upgrade in its place?
A. That's all you do if you have a 386DX computer. Removal tools are provided for you to remove the 386DX processor and place our Cyrix Upgrade in the processor socket. If you have a 386SX computer, the 386SX processor is soldered to your computer's motherboard and you cannot remove it. Our SX upgrade will simply snap over the top of it. No removal tools are necessary.

Q. How will my upgraded 386 compare to a "true" 486?
A. This is usually a question concerning performance. Comparisons must be relative. If you have upgraded a 386SX-16MHz PC with the Upgrade and are comparing it to a 486DX-33, you'll see that the upgraded system runs much slower. This has to do with the width of the external address bus, the size and speed of memory on both computers, the inclusion of an external cache on the 486 as well as other factors. The important questions are: how much faster is the computer functioning now compared to the way it was before it was upgraded, and is this increase a good value for you?

Q. What are some of the compatibility issue I need to know about?
A. There are several points to consider:
  • The original Intel 386SX-16MHz processor does not have a float pin, which the Cyrix Upgrade must have in order to work. The Cyrix Upgrade uses this pin to disable the processor and take over the processing. This is only an issue on 386SX-16MHz computers.
  • Older 387 math coprocessors may cause the system to stall and should be replaced with a new 387.
  • The Cyrix Upgrade will not work with 386 computers that only use a 287 math coprocessor. The 287 will have to be removed.
  • The Cyrix Upgrade will not work in Sun workstations.
  • The Cyrix Upgrade has been tested on many platforms. Within manufacturer models and lines, there can be slight differences that will allow the Upgrade to work well on one machine and not on another, although outwardly they may appear identical.

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