Yup I picked up a cheap 2nd hand 16Gb one on ebay, using it to cache my sata3 ssd with primocache through a pcie 1x slot, getting a hitrate of 90-95% easy with very low overhead from primocache.
Optane+SSD
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CrystalDiskMark 6.0.2 x64 (C) 2007-2018 hiyohiyo
Crystal Dew World :
https://crystalmark.info/
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* MB/s = 1,000,000 bytes/s [SATA/600 = 600,000,000 bytes/s]
* KB = 1000 bytes, KiB = 1024 bytes
Sequential Read (Q= 32,T= 1) : 778.924 MB/s
Sequential Write (Q= 32,T= 1) : 152.735 MB/s
Random Read 4KiB (Q= 8,T= 8) : 760.510 MB/s [ 185671.4 IOPS]
Random Write 4KiB (Q= 8,T= 8) : 154.520 MB/s [ 37724.6 IOPS]
Random Read 4KiB (Q= 32,T= 1) : 476.163 MB/s [ 116250.7 IOPS]
Random Write 4KiB (Q= 32,T= 1) : 154.202 MB/s [ 37647.0 IOPS]
Random Read 4KiB (Q= 1,T= 1) : 163.904 MB/s [ 40015.6 IOPS]
Random Write 4KiB (Q= 1,T= 1) : 85.815 MB/s [ 20950.9 IOPS]
Test : 1024 MiB [C: 12.2% (23.7/193.6 GiB)] (x5) [Interval=5 sec]
Date : 2019/07/24 18:17:53
OS : Windows 10 [10.0 Build 18362] (x64)
SSD only
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CrystalDiskMark 6.0.2 x64 (C) 2007-2018 hiyohiyo
Crystal Dew World :
https://crystalmark.info/
-----------------------------------------------------------------------
* MB/s = 1,000,000 bytes/s [SATA/600 = 600,000,000 bytes/s]
* KB = 1000 bytes, KiB = 1024 bytes
Sequential Read (Q= 32,T= 1) : 552.442 MB/s
Sequential Write (Q= 32,T= 1) : 478.827 MB/s
Random Read 4KiB (Q= 8,T= 8) : 219.707 MB/s [ 53639.4 IOPS]
Random Write 4KiB (Q= 8,T= 8) : 282.583 MB/s [ 68990.0 IOPS]
Random Read 4KiB (Q= 32,T= 1) : 218.333 MB/s [ 53304.0 IOPS]
Random Write 4KiB (Q= 32,T= 1) : 220.334 MB/s [ 53792.5 IOPS]
Random Read 4KiB (Q= 1,T= 1) : 30.860 MB/s [ 7534.2 IOPS]
Random Write 4KiB (Q= 1,T= 1) : 92.158 MB/s [ 22499.5 IOPS]
Test : 1024 MiB [C: 12.2% (23.7/193.6 GiB)] (x5) [Interval=5 sec]
Date : 2019/07/24 18:26:40
OS : Windows 10 [10.0 Build 18362] (x64)
I'm using a readonly cache so the write speeds don't matter for me, and the read speeds are vastly superior to my ssd in all benches especially 1Q1T 4k reads.