Reply 60 of 562, by IanB
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As promised, here are some details on CPU upgrades:
There are four possible 486 compatible CPUs from Cyrix / Texas instruments that can be used to upgrade the T5200's Intel 386 processor (Texas Instruments made the CPUs for Cyrix and sold them under their own brand as well):
CX486DLC / TX486DLC The Cyrix or Texas Instruments DLC upgrade. It was available in a variety of speed grades, e.g. 20, 25, 33 & 40 Mhz and has 1KB of cache that requires hardware modifications to fully support the cache. Any of those speeds should work on the T5200 but will only run at 20Mhz
CX486DRx2 This is the retail upgrade made by Cyrix and has clock doubling built in. It was available in various speed grades, 16/32, 20/40 & 33/66 etc. so when run on a 16 Mhz bus you get 32Mhz CPU, on a 20Mhz bus you get 40Mhz CPU and on a 33Mhz bus you get 66Mhz CPU etc. This also has 1KB of cache and has special circuitry built in so that no hardware modifications are necessary to support the cache. You would need a minimum of 20/40 to run on a T5200
TX486SXLB-040S-GA This is the ultimate upgrade and is a version of the DLC processor made by TI that has 8KB of cache instead of 1KB. It also has a clock doubling setting so can either be run at full 40Mhz on a 40Mhz bus or run at 40Mhz on a 20Mhz bus (the latter is suitable for the T5200) To get the best out of this chip you have to do the hardware mods, but even without them it still outperforms the DLC chip and gives similar performance to the CX486DRx2.
TX486SXL2B-050S-GA which is similar to the above but rated for 25/50Mhz and would also work on the T5200 but only run at the same speed as the above (20/40)
Note these last two part numbers have to be exact as one different letter or number means a different version. e.g. without the second "S" you get them in a 486 pinout instead of a 386 pinout. Unfortunately TI didn't print the full part number on the chip so you might have to confirm that you are buying the right version visually by checking the package and number of pins (386 size PGA 132 which has 14 pins on a side, not 486 size PGA 168 which has 17 pins on a side:
Here are some comparisons using the DOOM timedemo benchmark "doom -timedemo demo2". This doesn't necessarily show the best results for the faster CPUs as it is limited by the speed of the screen and more CPU bound tasks would likely show different results but it should give a rough idea of relative performance.
80386 @ 20 Mhz
44044 realticks
CX486DLC @ 20Mhz no hardware mods
20583 realticks
CX486DLC @ 20Mhz with flush and a20 mods
19866 realticks
CX486DRx2 @ 40Mhz (clock doubled) no hardware mods
16245 realticks
CX486DRx2 @ 40Mhz (clock doubled) with flush and a20 mods
16204 realticks
TX486SXLB-040S-GA @ 40Mhz (clock doubled) no hardware mods
16963 realticks
TX486SXLB-040S-GA @ 40Mhz (clock doubled) with flush and a20 mods
14122 realticks
The TX486SXL2B-050S-GA will perform identically to the TX486SXLB-040S-GA and as you can see from the above, the hardware mods only really benefit those processors but even without them they are still better than the DLC.
These processors run quite hot so it would probably a good idea to stick a low profile heatsink on them although they should work OK without one.
My patched BIOS detects and configures all the above automatically and will also detect if the hardware mods have been made and configure them to make use of the mods. (I'll describe the mods in a later post.)
I've updated the BIOS patches to V1.2 and posted new versions at the bottom of the first page of this thread:
Toshiba T5200 mods and upgrades
