| Q: | Exactly what is the Am5x86™-133 and what is the ordering part number?
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| A: | The Am5x86-133 is a 32-bit SL Enhanced CPU which runs on a 33MHz bus with 16KB internal cache that supports write back and write through cache policies. The pin-out of the Am5x86-133 is the same as the AMD Am486®DX4 Enhanced (SV8B family) of CPUs.
The exact ordering part numbers for the Am5x86-133 are listed below:
- AMD-X5-133ADW (168-pin PGA package, 3.45 volt, 55C case temp.)
- AMD-X5-133ADZ (168-pin PGA package, 3.45 volt, 85C case temp.)
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| Q: | I am having problems with my motherboard jumper settings. Can AMD help to determine the best settings?
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| A: | We cannot answer motherboard specific questions, such as how to set jumpers or configure your CMOS setup. You need to contact the motherboard manufacturer or consult your motherboard manual. 386 motherboards do not support 486 CPUs and will require a new motherboard. |
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| Q: | How can I tell if my motherboard supports the Am5x86-133?
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| A: | If your motherboard supports the AMD Enhanced line of 486 CPUs (the SV8B family) it will PHYSICALLY support our Am5x86-133. The BIOS may have to be upgraded to run the Am5x86-133 in clock x4 mode since the CPU ID changes in this mode. The proper setting for a motherboard that supports the Enhanced AMD CPUs would be the "AMD Enhanced DX2-66SV8B". However the BIOS on motherboards that properly support our Enhanced CPUs should be fully compatible with the Am5x86-133 running in clock x3 mode since the CPU ID is the same as the Enhanced 486 CPUs. In this case the Am5x86-133 could be run as a DX4-100 or DX4-120 and get the benefit of the 16KB internal write back cache even if the BIOS will not support the device in clock x4 mode. This device is 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 P24D or P24T. In the P24D or P24T configuration you need to verify that the voltage is still set for 3.45 volts since the Intel devices use a 5 volt operating voltage. On some motherboards the jumper configuration for the AMD Am5x86-133 CPU is the same as for the Intel P24D device. It is generally easier to use the AMD device with a motherboard that is designed to support it. Some of the older motherboard BIOS may incorrectly identify our device as another manufacturer’s part and cause the system to fail. |
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| Q: | What is the external bus speed for the Am5x86-133?
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| A: | The external bus speed is 33MHz. The Am5x86-133 CPU multiplies the input clock by 4!
The CLKMUL pin on the older 486 Enhanced CPUs was high for x3 mode and low for x2 operation. On the Am5x86-133 it is still high for x3 mode and should be jumpered low for the x4 mode of operation. |
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| Q: | After I installed the AMD CPU I seem to have some problems. Do you have any suggestions?
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| A: | 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 the wrong voltage or setting up the motherboard CPU configuration jumpers incorrectly can cause these types of problems to occur. |
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| Q: | My CPU seems to run fine but the BIOS reports a different type. Why?
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| A: | If your BIOS reports your Am5x86-133 as a different type of CPU, you may have a BIOS error or jumpers on the motherboard may not be set correctly. To update an old BIOS you will need to get an update from the motherboard or BIOS vendor. |
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| Q: | My system seems to run for a while and then fails. Any ideas?
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| A: | If the board runs properly for some period of time and then seems to fail you may have a thermal problem. The Am5x86-133 requires 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 33MHz select clock/4 and for bus speeds of 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 if the motherboard does not properly support the SL Enhanced power management features. The Am5x86-133 CPU does support the industry standard 2-pin SMM mode. |
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| Q: | I seem to have problems with my VL cards. Is this a CPU problem?
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| A: | No. You should be sure that the motherboard is jumpered for VL bus clock <=33MHz. If you still have problems you should try inserting / removing each of the Local Bus cards on your motherboard until the system works. You may need to contact the failing adapter card manufacturer to see if VL bus wait states are required for their card. |
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| Q: | Some of my programs work with the older CPUs but fail with my new one. What could cause this to occur?
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| A: | Some older benchmarks and diagnostic software do not work correctly with the faster processors. If you are having problems running specific programs 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. |
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| Q: | Does the Am5x86-133 support Pentium Code?
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| A: | The Am5x86-133 is a high performance 486, 32-bit processor achieving performance results equal to a Pentium 75. Applications that require Pentium instruction will not run on a 486. |
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| Q: | What would the speed comparison be if the processor was placed in a computer not supporting write back caching?
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| A: | The performance for the CPU would be about 8% lower if the internal L1 cache is operated in write through only policy. At the system level this would probably result in a 2% to 4% overall performance impact. |
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| Q: | Whenever I plug my SCSI drive in my 5x86-P75 stops working correctly. Why?
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| A: | Unfortunately, most VL motherboard chipsets cannot process DMA transfers while using the write back cache policy under a SCSI bus mastering environment. This is not a problem with your CPU or with your SCSI device. The problem should be reported to your chipset vendor. You can try to use the write through cache mode and that may clear the issue. |
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| Q: | What are the benchmark numbers for the Am5x86-133 CPU?
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| A: | The benchmarks for the Am5x86-133 CPU are listed below:
- Winstone '96 (Units) 44.4
- WinBench '96 CPUMark16 145.0
- WinBench '96 CPUMark32 151.0
- System Configuration - Gigabyte GA486AM Motherboard, 256KB L2 cache (15nS), 16MB DRAM (70nS), Diamond Stealth 2 MB VRAM video card
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| Q: | What is the difference between the AMD-DX5-133 and the Am5x86-P75?
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| A: | While the Am5x86-P75 was designed for the PC desktop market, the AMD-DX5-133 is a low profile surface-mount version of the desktop PGA Am5x86-P75. This device is intended for high performance embedded applications and comes in a 208-pin SQFP package. |
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