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AMD-751 system controller revision guide publication # 22564 rev: b-1 issue date: february 2000 tm preliminary information
preliminary information trademarks amd, the amd logo, and combinations thereof, amd athlon, AMD-751, and amd-756 are trademarks of ad- vanced micro devices, inc. other product names used in this publication are for identification purposes only and may be trademarks of their respective companies. ? 2000 advanced micro devices, inc. all rights reserved. the contents of this document are provided in connection with advanced micro devices, inc. (?amd?) products. amd makes no representations or warranties with respect to the accuracy or completeness of the contents of this publication and reserves the right to make changes to specifications and product descriptions at any time without notice. no license, whether express, implied, arising by estoppel or otherwise, to any intellectual property rights is granted by this publication. except as set forth in amd?s standard terms and conditions of sale, amd assumes no liability whatsoever, and disclaims any express or implied warranty, relating to its products including, but not limited to, the implied warranty of merchantability, fitness for a particular purpose, or infringement of any intellectual property right. the amd products described herein may contain design defects or errors (?product errata?) that causes the amd products to deviate from published specifications. currently characterized product errata may be available upon request. amd?s products are not designed, intended, authorized or warranted for use as components in systems intended for surgical implant into the body, or in other applications intended to support or sustain life, or in any other applica- tion in which the failure of amd?s product could create a situation where per- sonal injury, death, or severe property or environmental damage may occur. amd reserves the right to discontinue or make changes to its products at any time without notice.
1 22564b-1?february 2000 AMD-751? system controller revision guide preliminary information AMD-751? system controller revision guide the purpose of the AMD-751? system controller revision guide is to communicate updated product information on the AMD-751 ? system controller to designers of computer systems and software developers. this guide consists of three major sections: product marking identification: this section, which starts on page 2, provides product types, product revisions, opns (ordering part numbers), and product marking information. product errata: this section, which starts on page 3, provides a detailed description of product errata, including potential effects on system operation and suggested workarounds. an erratum is defined as a deviation from the product ? s specification. a product errata may cause the behavior of the AMD-751 system controller to deviate from the published specifications. revision determination: this section, which starts on page 11, describes the registers that identify the current revision of the part. technical and documentation support: this section, which starts on page 12, provides a listing of available technical support resources. revision guide policy occasionally amd identifies deviations from or changes to the specification of the AMD-751 system controller. these changes are documented in the AMD-751 system controller revision guide as errata. descriptions are written to assist system and software designers in using the AMD-751 and corrections to amd ? s documentation on the AMD-751 system controller are included. this release documents currently characterized product errata.
2 AMD-751 ? system controller revision guide 22564b-1 ? february 2000 preliminary information 1 product marking identification 1.1 production marking AMD-751 tm AMD-751ac b date code amd 1999 c product revision family/core AMD-751 package type a = plastic ball grid array c = commercial temperatur e range case temperature table 1. valid combinations for ordering parts opn package type operating voltage case temperature AMD-751ac 492-pin pbga atx 3.135 v?3.6 v 85 c note: valid combinations are configurations that are or will be supported in volume for this device. consult the local amd sales office to confirm availability of specific valid combinations and to check on newly released combinations.
3 22564b-1 ? february 2000 AMD-751 ? system controller revision guide preliminary information 2 product errata this section documents AMD-751 system controller product errata. a unique tracking number for each erratum has been assigned within this document for user convenience in tracking the errata within specific revision levels. table 2 cross-references the revisions of the processor to each erratum. an ? x ? indicates that the erratum applies to the revision. the absence of an ? x ? indicates that the erratum does not apply to the revision. note: there can be missing errata numbers. errata that have been resolved from early revisions of the controller have been deleted, and errata that have been reconsidered may have been deleted or renumbered. table 2. cross-reference of product revision to errata erratum number and description revision number c3 c5 pci 1 invalid read performed after a slave pci target abort x x 2 arbitration latency due to no bus preemption x 3 pci arb_dis bit set when dma is active x x agp 8 gart requestors do not work with tlb caches off x x 18 burst writes to non-existent agp memory hang system x x 20 agp ad_stb[1:0] strobe glitch with nvidia nv10-based (geforce) cards x x sdram 19 setting the queue bypass-mode bit causes memory failure x 21 potential memory failure when using certain double-sided sdram memory dimms x x amd athlon? system bus 12 incomplete amd athlon system bus disconnect causes AMD-751 to hang x x functional 14 bar0[3] initial setting causes os/2 warp install error x x 15 ref_5v cannot be at a lower voltage than vcc (3.3v) x
4 AMD-751 ? system controller revision guide 22564b-1 ? february 2000 preliminary information 1 invalid read performed after a slave pci target abort products affected. c3 and c5 description. when the AMD-751 system controller initiates an unaligned doubleword pci i/o read transaction and this i/o read receives a target abort from the pci slave, the next pci i/o read returns incorrect data. aligned transactions are unaffected. potential effect on system. a target abort on the pci bus is an extremely rare event and the occurrence of the abort is considered a catastrophic error condition. this condition was artificially created for pci testing and has not been observed in normal system validation testing. suggested workaround. none resolution status. fixed in a future revision of the AMD-751 system controller. 2 arbitration latency due to no bus preemption products affected. c3 description. the AMD-751 pci arbiter can impose long latencies on external pci bus masters when any master that currently owns the bus is attempting long transfers due to not correctly supporting bus preemption. when a pci master ? s bus grant is active and another master requests the bus, the arbiter should immediately deassert the grant to the first master, thus preempting the first master. the first master is permitted to continue bus transactions for the duration of its master latency timer. due to the anomaly in the arbiter, the original master does not get preempted if it owns the bus and it continues to keep its request pin asserted. therefore, it could use the bus indefinitely. however, this problem has not been seen with any real system hardware and software. potential effect on system. some peripherals may experience timeouts. a lack of fairness on the bus. suggested workaround. none resolution status. fixed in rev c5.
5 22564b-1 ? february 2000 AMD-751 ? system controller revision guide preliminary information 3 pci arb_dis bit set when dma is active products affected. c3 and c5 description. if dma is active when arb_dis is set, the system can hang. potential effect on system. system hang could occur. suggested workaround. prior to setting arb_dis, software suspends all dma activity. resolution status. fixed in a future revision of the AMD-751 system controller . 8 gart requestors do not work with tlb caches off products affected. c3 and c5 description. only partial support exists for the mode where gart tlb caches are disabled. gart caches disabled was intended primarily for performance evaluation, and is not supported. potential effect on system. none suggested workaround. the bios should set bar1: offset 02h bit 2. resolution status. none required, proper operation
6 AMD-751 ? system controller revision guide 22564b-1 ? february 2000 preliminary information 12 incomplete amd athlon system bus disconnect causes AMD-751 to hang products affected. c3, c5 description. an incomplete amd athlon ? system bus disconnect sequence (from the amd athlon processor) can hang the AMD-751 system controller. the amd athlon may not complete a disconnect sequence when using stpclk-throttling power management . potential effect on system. this problem can occur with acpi thermal zone support (thermal-throttling power management) or processor c2/c3 support enabled. suggested workaround. stpclk throttling (thermal zone) and processor c2/c3 are not supported at this time. stpclk throttling is not required for support of the acpi s1 state. resolution status. fixed in c3.
7 22564b-1 ? february 2000 AMD-751 ? system controller revision guide preliminary information 14 bar0[3] initial setting causes os/2 warp install error products affected. all revisions description. bar0[3] (base address register 0 = function 0, device 0, offset 10h) is initialized to 1, which indicates that the agp aperture is prefetchable. with all base address bits (bits 4 ? 30) reset and with bit 3 set to 1, os/2 warp 4.0 installation hangs. with agp disabled, these bit settings are correct for the AMD-751. potential effect on system. os/2 warp 4.0 hangs during installation. suggested workaround. enable agp bios settings during the os/2 warp 4.0 installation. when the bios sets the base address bits of bar1 for agp mode, os/2 warp 4.0 loads correctly. resolution status. no change to the AMD-751 is required. 15 ref_5v cannot be at a lower voltage than vcc (3.3v) products affected. c3 description. voltage on the vcc (3.3-v supply) pins cannot exceed the voltage on the 5-v reference pin (ref_5v). potential effect on system. the AMD-751 can go into a latch-up state, and permanent damage to the part may result. suggested workaround. specify the system power supply whose outputs ramp up and ramp down, such that the 3.3v outputs never supply voltage higher than the 5-v outputs. for more information, see the amd athlon ? processor voltage regulation application note , order# 22651. in addition, providing a forward-biased diode on the motherboard from the 3.3-v supply to the 5-v supply limits any 3.3-v excursions to the diode voltage drop. the power supply connector should never be inserted or removed while power is applied to the motherboard. resolution status. fixed in rev c5.
8 AMD-751 ? system controller revision guide 22564b-1 ? february 2000 preliminary information 18 burst writes to non-existent agp memory hang system products affected. c3 and c5 description. running in dos under windows, mechwarrior2 creates burst writes to non-existent agp memory that intentionally cause master abort cycles from the s3 savage4 graphics card to the system controller. the AMD-751 system controller does not handle master abort cycles in the quantity generated by the s3 savage4 graphics card. this behavior to the system controller is caused by the software/driver when write combining is enabled and is not considered appropriate nor indicative of any common software technique. write combining is enabled when the amd agp miniport driver is installed. potential effect on system. system hangs. suggested workarounds. i. run the game differently: 1. install and run the game directly under dos, creating a boot floppy when asked. 2. obtain the windows version of the program on cd. 3. upgrade to the newer mechwarrior3 product. ii. change the bios 1. apc write chaining, device 0, function 0, register 84h, bit 17 must be left at 0. resolution status. no planned fix .
9 22564b-1 ? february 2000 AMD-751 ? system controller revision guide preliminary information 19 setting the queue bypass-mode bit causes memory failure products affected. c5 description. a memory failure may occur if queue bypass mode is enabled. potential effect on system. memory failure, which causes a system error. suggested workaround. do not set the queue bypass-mode bit. resolution status. fixed in a future revision of the AMD-751. 20 agp ad_stb[1:0] strobe glitch with nvidia nv10-based (geforce) cards products affected. all revisions (c3 and c5) description. the AMD-751 system controller ? s ad_stb[1:0] signals may experience noise due to strong drive strengths. this noise may result in signal glitches, causing incorrect information to be strobed into the agp adapter. potential effect on system. system hangs. suggested workaround. the issue can be alleviated by forcing the agp subsystem into agp 1x mode. a driver update is available from nvidia that performs this task by changing the system registry. performance will decrease when enabling the lower speed agp mode. to obtain this driver, go to the www.nvidia.com website, and follow the driver update links from the home page. please contact your amd specialist for details. resolution status. fixed in a future revision of the AMD-751 system controller.
10 AMD-751 ? system controller revision guide 22564b-1 ? february 2000 preliminary information 21 potential memory failure when using certain double-sided sdram memory dimms products affected. c3 and c5 description. under certain sdram double-sided dimm loading conditions, systems based on the the AMD-751 system controller can experience reduced timing margins, resulting in memory failures during memory cycles. this condition only occurs when using specific double-sided dimms with combinations of the following characteristics: 1. printed wiring board (pwb) designed around the intel lc_12_112 gerber. 2. memory ics with lower v il input thresholds. potential effect on system. unstable system. suggested workarounds. 1. vendors should use memory dimms only from an approved vendor list (avl). dimms from this list have been extensively tested on AMD-751 based platforms and qualified for usage. please consult your oem or amd specialist for details. 2. vendors developing new AMD-751 based motherboards should implement pulldown resistors on the maa[14:0] and mab[14:0] address buses. use of this termination method will improve the timing margins. please consult your oem or amd specialist for specific values. resolution status. all future motherboards should be implemented with the suggested termination method .
11 22564b-1 ? february 2000 AMD-751 ? system controller revision guide preliminary information 3 revision determination table 3 summarizes the AMD-751 system controller configuration register offsets, devices, default values after reset, and access types. access types are indicated as follows: rw - read/write ro - read only this read-only value is defined as 1022h. this read-only value of 7006h represents the AMD-751 system controller single processor device. bits 7 ? 0 AMD-751? system controller revision code (ro) - the most-significant nibble indicates the die revision and the least-significant nibble represents the stepping. (for example, 00h = revision a0; 01h = revision a1; 10h = revision b0; 21h = revision c1; 25h = revision c5; etc.) table 3. function 0, device 0 configuration registers offset cache control reset access 01h ? 00h vendor id (amd) 1022h ro 03h ? 02h device id single processor device 7006h ro 08h revision id nn * ro 63h ? 60h biu status and control 0000_0cxxh rw 86h pci and apci chaining 00h rw note: * nn changes for each device revision. for example, 00h = revision a0; 01h = revision a1; 10h = revision b0; 21h = revision c1; 25h = revision c5 etc. vendor id device 0 offset 01h ? 00h bit 1514131211109 8 7654321bit 0 vendor id reset0001000000100010 device id device 0 offset 03h ? 02h bit 1514131211109 8 7654321bit 0 device id reset0111000000000110 revision id device 0 offset 08h bit 7 6 5 4 3 2 1 bit 0 AMD-751 system controller chip revision and stepping code reset ????????
12 AMD-751 ? system controller revision guide 22564b-1 ? february 2000 preliminary information 4 technical and documentation support 4.1 documentation support the following documents provide additional information regarding the operation of the AMD-751 system controller: AMD-751 ? system controller data sheet (order# 21910) amd-756 ? peripheral bus controller data sheet (order# 22548) amd athlon ? system bus specification (order# 21902) amd athlon ? processor bios, software, and debug tools developers guide (order# 21656) amd athlon ? processor data sheet (order# 21016) for the latest updates, refer to www.amd.com and download the appropriate files. for documents under nda, please contact your local sales representative for updates.

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