| D: | Can I run an Am486® CPU in a 5 volt socket?
|
| R: | The AMD 3.45 volt processors will not operate in 5 volt sockets. Most older motherboards do not support 3.45 volt processors. Check your manual. |
|
|
| D: | What are the bus speeds for the AMD CPUs?
|
| R: | The bus speed for the Am486DX2-66 is 33MHz, the Am486DX2-80 is 40MHz, the Am486DX4-100 is 33MHz and the Am486DX4-120 is 40MHz. The Am486DX2 class CPUs multiply the input clock by 2 and the Am486DX4 class devices multiply the input clock by 3! |
|
|
| D: | After I installed the AMD CPU I seem to have some problems. Do you have any suggestions?
|
| R: | If you are having problems running HIMEM.SYS or DOS4GW.EXE check your motherboard CPU voltage and type settings. Running a 3.45 volt CPU at 5 volts or running a non-SL enhanced CPU as an SL enhanced part can cause these types of problems to occur. |
|
|
| D: | My CPU seems to run fine but the BIOS reports a different type. Why?
|
| R: | If your BIOS reports your Am486DX4-100 as a 486DX2-100 or reports your Am486DX4-120 as a 486DX4-100 you may have a BIOS error or jumpers on the motherboard may be set incorrectly. To update an old BIOS you will need to get an update from the motherboard or BIOS vendor. |
|
|
| D: | My system seems to run for a while and then fails. Any ideas?
|
| R: | If the board runs properly for some period of time and then seems to fail you may have a thermal problem. The Am486DX2-80 requires a heat sink and the Am486DX4 class CPUs require a heat sink and fan. You will need to apply a thin layer of heat sink paste to assure proper heat transfer from the CPU to the heat sink.
If you have intermittent problems check that the ISA bus clock is near 8MHz. The divider is in the Advanced CMOS setup. For bus speeds of 25MHz select clock/3, for 33MHz select clock/4 and for 40MHz select clock/5.
Some green motherboards may try to slow down the processor. It may be necessary to disable power management on Green PC motherboards to eliminate intermittent problems. The AMD standard 486 class processors do not support SMM mode (also called SL Enhanced). The Enhanced Am486 CPUs from AMD do support SMM mode. |
|
|
| D: | I seem to have problems with my VL cards. Is this a CPU problem?
|
| R: | No. If you have problems running with a Local Bus motherboard, try running the same motherboard at 33MHz and set the Local Bus clock rate indicator jumper for <=33MHz. If this works the problem probably lies with one or more of the Local Bus cards. Try inserting / removing wait states until the processor works properly. If the board works at 33MHz, switch the frequency to 40MHz, set the Local Bus clock rate indicator jumper for >33MHz, and try inserting / removing each of the Local Bus cards on your motherboard until the system works. Some Local Bus cards will not operate properly at 40MHz. |
|
|
| D: | Some of my programs work with the older CPUs but fail with my new one. What could cause this to occur?
|
| R: | Some older benchmarks and diagnostic software do not work correctly with the faster processors. If you are having problems running specific programs at 80MHz or 100MHz, you may need to contact the respective software company to determine if there is an updated version of their software available.
The AMD 80486 microprocessors are fully software compatible with programs written for the x86 microprocessors. |
|
|
| D: | Are there any special precautions that I should take when running my benchmark programs?
|
| R: | Yes. Be sure to turn off all power management options in the CMOS so that the system does not try and slow the processor down during your benchmark operations. |
|
|
| D: | How can I tell if I have a 3.45 volt or 5 volt CPU?
|
| R: | The A80486DX2-80 V8T and A80486DX2-80NV8T are 3.45 volts devices and the A80486DX2-80 and A80486DX2-80N are 5 volt parts. All of our DX4 class cpu's are 3.45 volts. If you plugged a 3.45 volt part into a 5 volt board, it may be damaged. |
|
|
| D: | My CPU seems to run slower than I expected. Why is that?
|
| R: | If your processor is running faster or slower than it should, check that pin B-13 (Bravo 13) is grounded for DX2 processors. It should be high for DX4 processors. The DX2-80 will not run reliably at 100MHz. If your computer doesn't boot, try setting the clock speed to 25MHz. If this works, pin B13 is not grounded. Use your favorite benchmark program to determine if the speed is correct. Also, check if the cache is enabled in your advanced CMOS setup. For DX4-100 the cache wait states should be 0. Your motherboard manual should indicate a special jumper setting for the Am486DX2 microprocessor. If no jumper exists, then your motherboard may not correctly support the Am486DX2 processor.
If your CPU's performance is much lower than expected you may need to reduce wait states in your cache or main memory. In many cases the cache wait states may be set to zero for bus speeds of 33MHz or less.
For example if you have the Am486DX4-100 you should get a benchmark result of 198 with Norton SI version 8.0. If you are getting a number of 132 or 134 instead you should try the following to see if it helps.
Change the cache read cycle time from 2 to 1 and the cache write cycle time from 3 to 2. Some customers have reported that changing the cache write wait state from 1 to 0 will also correct the problem. Also, changing the DRAM speed from fast to fastest may fix the problem. If these changes don't help you will need to contact your board vendor for assistance.
Note: Running the Am486DX2 CPU faster than its rated speed will result in unreliable operation. |
|
|
| D: | How can I tell if the device I have is an Enhanced Am486 part?
|
| R: | The part number suffix for the AMD Enhanced 486 product line is SV8B with the S indicating that the part is "SL Enhanced", the V indicating that the part is a "3.45 volt" device and the 8B indicating that the internal cache is "8KB Write Back" capable.
These devices are fully pin compatible with the Intel® SL enhanced 486 device. You may be able to use this part in a motherboard that does not specifically support the AMD part by setting up your motherboard for an Intel 486DX4-100 SL Enhanced CPU like the P24C, P24D or P24T. On some motherboards the jumper configuration for the AMD Enhanced CPU is the same as for the Intel P24D device. It is generally easier to use the AMD devices with a motherboard that is designed to support them. Some of the older motherboard BIOS may incorrectly identify our device as another manufacturer’s part and cause the system to fail.
In order to be sure that you can run the AMD Enhanced CPU you should use one of the motherboards that AMD has tested for full compliance with our Enhanced CPU design recommendations. |
|
|
| D: | What clock frequencies are available in the Enhanced Am486 products?
|
| R: | The AMD Enhanced 486 product line includes 80MHz, 100MHz and 120MHz CPUs. These are the A80486DX2-80SV8B (40MHz x 2), A80486DX4-100SV8B (33MHz x 3) and the A80486DX4-120SV8B (40MHz x 3). |
|
|
| D: | Can the Enhanced Am486 products be used in older motherboards designed for the standard 486 CPU?
|
| R: | This really depends on the motherboard. The Enhanced AMD 486 CPUs have been designed so that all of the new features (SMM, Stop Clock, Write Back L1 Cache, etc) will be disabled if the socket does not support them. However, if the motherboard has done something non-standard with the 486 socket the device may not run correctly. It is best to use a motherboard that is designed for the new devices to get the best performance out of them. If the BIOS incorrectly identifies our device as another manufacturer’s part it may cause the system to fail. |
|
|
| D: | My AMD Enhanced Am486DX4-120 CPU gives a Norton SI version 8.0 rating of around 118. Shouldn't it be much higher?
|
| R: | Yes. This benchmark number should be about 259.3. The problem may be in the BIOS settings. You may want to check the following settings in your BIOS.
The cache read burst cycle time should be 3-1-1-1 and the cache write wait state should be 0. You will need to disable the auto configure mode in your BIOS to make these changes. If this doesn't work you will need to contact your board vendor for help. |
|
|
| D: | My system floppy drive will not work properly unless I disable the L1 internal cache on my AMD Enhanced CPU. Is this a problem with the CPU?
|
| R: | No. This is most likely a problem with the motherboard properly supporting the internal write back policy of the L1 internal cache on the Enhanced CPU. The floppy drive uses Direct Memory Access (DMA) for data transfer from the floppy to system memory. If the motherboard doesn't support the L1 cache write back policy properly you may have to jumper the motherboard for L1 cache write through policy only. You should contact the motherboard vendor to see if they are aware of the problem with the motherboard and to see if they have a fix for it. |
|
|
