Mixed RAM in Z620

[vectre]

Hey

A while back I posted about RAM in the Z620. I've now bought 8 x 8GB sticks which work great - all installed as per the data sheet here:

http://h20331.www2.hp.com/hpsub/downloads/z620_memory_configurations.pdf

I was hoping to still use 4 of the 4GB original RAM sticks, as pointed out in the dual processor chart with 80GB RAM - allocated to slots 2,4,5 and 7.

If I boot without these slots populated, it works fine - but if I put the 4GB sticks I've previously had instal;ed, it beeps and the MEM FAN led blinks.

Am I missing something here?

Many thanks

Chris

SPECS:

HP Z620 - 2 x Intel Xeon E5-2620 V2@2.10 GHz 6C, 48GB DDR3, 200 GB SSD+6 TB

• 2 x Intel Xeon E5-2620 V2 @ 2.10 GHz (2.60 GHz Max Turbo) 6 Cores (12 Threads) PER CPU
• 48 GB DDR3 ECC Memory @ 1600 MHz (12 x 4 GB)
• 200 GB Solid State Drive SAS (OS)
• 2 x 3 TB Hard Drive SAS (Storage)
• Nvidia Quadro K600 1 GB GDDR5 (1 x DVI + 1 x DP) Graphics Card
• DVD RW Optical Drive SATA
• Multi Card Reader
  
• HP SAS card
• On-Board Audio
• Gigabit Ethernet
• Microsoft Windows 10 Professional installed and activated

[BambiBoomZ]

Vectre,

I've used mixed size modules in both z420 and z620 systems successfully although the memory benchmarks were never as high as a completely uniform set. In a dual processor system, a symmetrical 4X 8Gb + 4X 8GB will be best. A larger capacity CPU0 RAM will have to have an extra 1-bit parity check to synchronize with CPU1 = latency.

Example:

HP z420_1 (2013) (Rev 1) > Xeon E5-1620 four core @ 3.6 /3.8GHz > 24GB DDR3 (4x4GB + 4X 2GB) ECC 1600 RAM > AMD V4900 (1GB) > Seagate 500GB > M-Audio 192 soundcard > Linksys WMP600N WiFi
[Passmark system rating = 2372 / CPU = 9001 / 2D= 712 / 3D= 1353/ Mem= 2261 / Disk= 712]

HP z420_1 (2013) (Rev 6): Xeon E5-1620 (4-core @ 3.6/3/8GHz) / 16GB (4X 4GB DDR3-1600 ECC unbuffered) / NVIDIA GeForce GTX 660 Ti / Samsung 850 Evo + WD Blue 2TB / ASUS Essence STX Sound card / 600W PSU > Windows 7 Professional 64-bit (HP OEM ) > Samsung 40" 4K TV as monitor
Passmark System Rating: = 4327 / CPU = 9594 / 2D = 705 / 3D = 4655 / Mem = 2433 Disk = 4686] [Single Thread Mark = 2003 [6.21.18]

Notice that the memory score with 16GB is higher than with 24GB of mixed size modules.

Consider checking every aspect that might vary between the 4GB and 8GB modules.  The most significant variation would be if one group was ECC unbuffered and the other ECC registered. In a dual processor system the RAM must be ECC registered. Other variations could be the  single or dual ranked, clock speed, an "L" power saving server specification, different timing /latency, or simply subtle variations by maker.

Starting with HP systems in 2009 and the seven total,  I had the benefit of having learned previously- in 1993- that workstations are very fussy about memory. My first computer, an IBM 486 DX2 50MHZ ($2,800) had a maximum RAM capacity of 3MB and could only use one model of IBM memory.  Each 1MB module cost $180 or $184,320 per GB.  BTW, the original 85MB HD was replaced- after four months- by a 540MB HD, which was the largest drive that DOS6 /Windows 3.1 could see that cost $527 or $999 / GB- over $1,000,000 /TB.  A 2008 Dell Precision T5400 (2X Xeon X5460)  was similarly fussy about RAM.  When I had the first modern HP system, a z420 with an E5-1650, I began using only completely identical HP-labelled modules and never have problems again.

Consider the goal of all, identical HP-labelled modules.

There may be a lot of theories about the problem, diagnostics to consider, comparison shopping, and etc., but how much system down-time, experimentation, and frustration is it worth?

BambiBoomZ

HP z620_2 (2017) (R9) > Xeon E5-1650 v2 (6C@ 4.4GHz) / z420 Liquid Cooling / 64GB (HP/Samsung 8X 8GB DDR3-1866 ECC registered) /GTX 1070 Ti 8GB / Samsung SM951 M.2 512GB AHCI + Samsung 970 EVO M.2 NVMe 500GB + HP/HGST Enterprise 6TB / Focusrite Scarlett 2i4 sound interface + 2X Mackie MR824 / 825W PSU / Windows 7 Prof.’l 64-bit (HP OEM) > 2X Dell Ultrasharp U2715H (2560 X 1440)
[ Passmark Rating = 6148 / CPU rating = 15952 / 2D = 787 / 3D= 13077 / Mem = 3045 / Disk = 15506 / Single Thread Mark = 2441 [6.10.21]

HP z420_3: (2015) (R12) Xeon E5-1650 v2 (6C@ 4.3GHz) / z420 Liquid cooling / 64GB (HP/Samsung 8X 8GB DDR3-1866 ECC registered) / NVIDIA GeForce GTX 1060 6GB/ Samsung SM951 M.2 256GB AHCI + Samsung 860 EVO 500GB + HGST 7K6000 4TB / ASUS Essence STX + Logitech z2300 2.1 / 600W PSU > Windows 7 Professional 64-bit (HP OEM ) > Samsung 40" 4K
[Passmark System Rating: = 5947 / CPU = 15268 / 2D = 773 / 3D = 11025 / Mem = 2931 Disk = 15530 /Single Thread Mark = 2383 [5.3.21]