On AMD 486DX family CPUs:
Am486DX4/100: While it only has 8k L1 cache, it runs much cooler than the Intel 486DX4/100, both clocked at 3x33.
Am486DX4/100 (Enhanced): This is an even lower powered version, known as the Am486DX4/100 S-version, which uses techniques similar to the Intel SL-enhanced 486DX2/50. This uses special microcode to switch off sections of the logic during execution, in a manner that is completely transparent to software, but with no penalty in performance (this is very distinct from software-controlled power-management like APM or ACPI). The S versions are the lowest-powered 486DX CPUs, and were used in notebooks and handhelds. Perhaps the Fujitsu uses these. You can tell them apart from the standard CPUs from their marking: SV8T/B (Enhanced), NV8T/B (Normal). 'T' indicates Write-through cache, 'B' Write-Back.
Am486DX4/120: Similar to the Am486DX4/100, but qualified for 3 x 40 = 120 MHz operation. Some of these devices (late production) apparently had 16k L1 cache.
AMD5x86/133: The fastest 486 CPU ever built, at 4 x 33 MHz. Selected examples will overclock comfortably to 3 x 50 = 150 MHz or even 4 x 40 = 160 MHz. These are also very cool running (since they included the enhanced S-version logic). In conjunction with their flexible multiplier and speed ratings, this is the reason behind their popularity for upgrades and overclocking.
Of course, it also possible to underclock these to 3 x 33 or 4 x 25 = 100 MHz, in which case they are similar in performance to an Intel486DX4/100, but consume less than 50% of the power. Also interesting is 3 x 40 = 120 or 2 x 50 = 100, both of which are higher-performance and lower-power than an Intel 486DX4/100.
All these CPUs need a voltage-adapter socket to upgrade a 5v 486DX socket. These sockets are still available for $20-$30. The 5x86/133 was also available in a PQFP (surface-mount) package which is very similar to the PQFP package of the Intel mobile SL-enhanced 486DX2/50. Replacing the 486DX2/50 with an AMD5x86/133 results in a cooler and faster running portable. This has created a cottage industry in upgrades for older notebooks with the Intel CPU, like the Thinkpad 755/C/Cs/CE/CD, 701/C/Cs, etc. (I have a 755CD with the AMD 5x86/133 upgrade, and it runs cooler and faster than the IBM Pentium/75 upgrade for the same notebook, which has a list price of about $1200!).