rev2 -- 11/2/92 486 Processor Questions and Answers Authors: Jim Gendreau, HP California PC Division Richard Jessup, HP Grenoble PC Division Comments to: Curt Gowan [HP CPCD] 75300,3400 Many questions have arisen about the various 486 IC's that Intel markets today. The following Q & A article may help clarify the situation. (Updated 11/2/92 - changes indicated by a bar | ) ------------ Q. Intel seems to make a lot of upgrade chips -- how are they different? A. Intel is marketing their "speed doubling" technology in several different products. DX2 chips are sold to Intel's OEMs (like HP) and OverDrive chips are sold directly to end-users. DX2 and OverDrive chips are available in two different pinouts. The chart below shows Intel's products: Intel Intel Product Part Number Package / Pinout --------------- -------------- ------------------ 40 MHz internal / 20 Mhz Local Bus speed (Vectra 486s only) SX OverDrive/20 ODP486SX-20 169 pin PGA / i487SX 50 MHz internal / 25 MHz Local Bus speed i486DX2/50 A80486DX2-50 168 pin PGA / i486DX SX OverDrive/25 ODP486SX-25 169 pin PGA / i487SX DX OverDrive/25 ODPR486DX-25 168 pin PGA / i486DX 66 MHz internal / 33 MHz Local Bus speed i486DX2/66 A80486DX2-66 168 pin PGA / i486DX SX OverDrive/33 ODP486SX-33 169 pin PGA / i487SX DX OverDrive/33 ODPR486DX-33 168 pin PGA / i486DX DX OverDrive/33 ODP486DX-33 169 pin PGA / i487SX Q. How do the two pinouts (i486DX and i487SX) differ? A. Two of the control pins are different, but the rest of the pins are the same. If an OverDrive or DX2 chip is installed in a socket designed for a different pinout, it will not work. HP 486 systems have "universal" sockets to provide maximum flexibility. | a) Vectra 486U: | The upgrade socket is in parallel to the primary socket and | is switch selectable for either pinout. | b) Vectra 486ST : | The upgrade is installed in the primary socket which is | switch selectable for either pinout. | c) Vectra 486N : The system autodetects and self-configures itself for any of the above types of 486 processors. Q. How can someone tell the difference between all of these chips? A. The DX2 chips have no built-in heatsink and have a distinctive DX2 label. The OverDrive chips have a distinctive OverDrive label and may have a built-in heatsink. To be sure what the chip is, compare the Intel part number on the chip to the ones in the chart above. Q. Does the 66 MHz chip upgrade require a heat sink? A. Yes - The Intel OverDrive/33 (66 MHz) chip has a built-in heatsink, so there is no need to add an additional one. If a DX2/66 type chip is used for the upgrade, an HP heatsink (p/n 1205-0855) and clip (p/n 1205-0854) should be installed. Q. The OverDrive heatsink is smaller than the HP heatsink on the 50 MHz primary chip, will it still work OK? A. Yes - The heatsink on the OverDrive chip is integrated into the chip, therefore it has excellent thermal transfer characteristics. The HP heatsink is clamped to the chip, which means the thermal transfer capabilities are less efficient than an integrated heatsink. HP therefore specified a larger heatsink to ensure that HP's reliability standards would be met. Both chips are adequately cooled to prevent chip failure. Q. Once I install the OverDrive chip can I remove the original 50 MHz chip on an HP Vectra 486U series PC? A. No - Doing so will void your warranty. Leaving the chip in will increase the reliability of the system -- the OverDrive/33 chip is somewhat sensitive to noise on the data lines; leaving the original chip in ensures that any noise is attenuated to meet HP reliability standards. The HP Vectra 486/66U ships with a filter board (p/n D2284-60001) plugged into the primary socket that does the same thing. The HP Vectra 486ST series PC has only one socket -- the filtering is built-in. The upgrade chip replaces the original chip. The HP Vectra 486N Series PC has only one socket. The board is also designed to accept a soldered version of the i486SX when it becomes available in the future) Until then, the upgrade chip will always replace the original, socket mounted chip. The SXOFF switch needs to be set only if a DX and a soldered SX processor are both present on the board simultaneously. Q. If the chip does not appear to work what can I do? A. Check the following things: o Is the chip aligned correctly in the socket? The beveled edge of the chip should be aligned with the arrow mark on the system board. o Is the chip fully seated in the socket? The best way to ensure this is to use the Intel chip removal tool to remove the chip (push the top of the tool toward the center - do not pull up), then put the chip back into the socket and push down firmly. Make sure the chip is correctly aligned as noted above. o Are the switches set correctly? See the next question for the correct settings. Q. How should the processor switches be set? A. The chart below shows which Intel upgrade chips can be installed in each type of HP Vectra and how the processor switches should be set for each type of chip: a) 486U Series. Pinout Clock Intel Intel -------------- Speed Product Part Number sw 1 sw 2 sw 3 ----------------------------------------------------------- i486DX2/50 A80486DX2-50 on on off i486DX2/66 A80486DX2-66 on on on | SX OverDrive/25 ODP486SX-25 off on off | SX OverDrive/33 ODP486SX-33 off on on DX OverDrive/25 ODPR486DX-25 on on off DX OverDrive/33 ODPR486DX-33 on on on | DX OverDrive/33 ODP486DX-33 off on on NOTE: There are TWO different types of OverDrive/25 chips and THREE different types of OverDrive/33 chips -- verify the switch settings are correct for the Intel part number being installed! b) 486ST-Series. Intel Intel VRAM CPU Video Product Part Number sw 1 sw 2 sw 3 sw 4 -------------------------------------------------------------- i486DX2/66 A80486DX2-66 off off off off SX OverDrive/33 ODP486SX-33 off off on off DX OverDrive/33 ODPR486DX-33 off off off off DX OverDrive/33 ODP486DX-33 off off on off NOTE: There are THREE different types of OverDrive/33 chips - Verify the switch settings are correct for the Intel part number being installed! a) 486N Series. Speed : Switch Block A Processor type Sw. 1 (MHZ-1) Sw. 2 (MHZ-2) -------------- ------------- ------------- i486SX/25 off on Any OverDrive/25 off on Any 486DX2/50 off on Any OverDrive/33 on on Any 486DX2/66 on on Pinout : Switch Block B Socketed processor Soldered processor Sw. 8 (SXOFF) ------------------ ------------------ -------------- none i486SX off i486DX or i486DX2 i486SX on all other combinations don't care Q. If the chip appears to be bad, what can I do? A. If the upgrade chip was purchased from HP, the chip is covered by both an Intel and an HP warranty. If the chip was purchased from Intel, ONLY Intel's warranty applies. The HP upgrade kit can be identified by the new system nameplate that is included with the chip kit. Proof of purchase may be required to use the HP warranty. o Intel provides an end user support line (800-321-4044, USA only, and 503-629-7354 or the local Intel distributor in your country for others) and can replace a chip that is determined to be bad. o The chip can be returned to HP or your dealer for a free exchange during the one year warranty period. o If the chip is installed in an HP system covered by the Vectra 486 one year on-site warranty, the chip can be replaced on-site by an HP System Support Engineer. The HP SSE will replace the chip | with the OEM version of the chip (an Intel DX2 chip - HP p/n 1821-0470) and an HP heatsink (p/n 1205-0855 and 1205-0854). Q. Why is the OverDrive chip labeled 33 MHz when it is really 66 MHz? A. Intel labels the OverDrive chips with the external local bus speed they support. Since all OverDrive chips have the "clock doubling" feature, it is assumed by Intel that everyone knows that the CPU runs at twice the bus speed internally. Note that the OEM version of these chips, the DX2, is labeled with the actual CPU speed. Q. Some of the OverDrive chips have the i486DX pinout. Can the i486DX processor in an HP Vectra 486/25T or 486/33T PC be replaced with an OverDrive processor to increase the performance? A. No - Although Intel's documentation indicates that this can be done, HP does NOT recommend that these systems be upgraded with OverDrive chips. Intel's tests found two Power-On Self-Test errors (0702 and 0707) that they chose to ignore. Intel's testing does not appear to be as comprehensive as HP's, which means the reliability of these systems with an OverDrive chip installed can not be ensured. Q. Can an HP Vectra 486s/20 be upgraded? A. Yes - The HP Vectra 486s/20 can be upgraded to 40 MHz by installing an Intel OverDrive/20 chip in the upgrade socket. Before the OverDrive chip can be installed in the system, the system BIOS must be updated to version M.03.01 or later using the HPUpdate utility disk. The BIOS update is included in the HP version of the OverDrive/20 upgrade (HP p/n D2170A). If the chip is purchased from Intel, the BIOS update must be purchased from the HP Corvallis Service Center (503-750-5856). The BIOS update part numbers are: D2165-60001 - 3.5" disk and D2165-60002 - 5.25" disks. Since the HP Vectra 486s/20 has an upgrade socket and a single speed local bus (20 MHz), there are no switches that need to be changed. As with the HP Vectra 486U series, the original processor should be left in the primary socket. * * *