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[May 27, 2003]
5th : Another 32MB(EDO type) board.
The 5th article is about the 32MB(EDO) board initially recognized as 16MB one, which is the difference from the one in the previous article. The 32MB board described in the 4th article has a feature such as being recognized as size zero during initial sequence before setting with a program. Sometimes, it causes a uncomfortable situation (as lack of memory area for booting up OS such as Win95), if you do not put the setting program (such as the over16s).
This article describes an improved type of 32MB board to avoid such uncomfortable situation. This 32MB board will be initially recognized as 16MB by the BIOS, and after rewriting the memory register with the setting program this will be reconstructed as 28MB (or 32MB).
Additional ICs.
This 32MB board needs also two ICs such as 74VHC08 and 74VHC32. However, in the right upper picture, different named ICs are shown. Occasionally, I could not get them above mentioned, and these different ICs have the same in functions and/or more faster.
74VHC11 has been used instead of 74VHC08, and 74LVC32 has been used instead of 74VHC32 respectively. Sure, you'll be able to use either of them !
Because the LVC type of HITACHI (about 1.9mm) is thicker than VHC type (about 1.5mm), it's not good to use instead of 74VHC08 or 74VHC11 as a rider. Thicker rider may cause the trouble such that the memory board will float from the main board at mounting.
Wiring diagram and additional circuits.
The left figures are the wiring diagram and additional circuits.
In the left figure, there is additional information that some of circuit lines on the 4MB board (from which old chips are removed) should be cut before mounting new chips. Those lines to cut are A8, A9, A10, A11 and *RAS2 from the connector. In the information, solid-lines mean existing on front (parts) side, and dotted-lines mean existing on rear side.
Before soldering pins , *UCAS, *LCAS, *OE, *WE and *RAS pins of 5113165x chips should be slightly lifted up for soldering more easily and for avoiding to touch on the board surface.
After those preparations, you may mount new chips.
(Comment : The value of capacitor may be anything from 0.33uF(micro Farad) to 3uF instead of 1uF.)
Setting to memory registers.
The additional OR circuit will act as a suppresser of *RAS3 at initial sequence. So, the BIOS will recognize only 16MB (half of 32MB) at initial sequence. After rewriting the contents of the memory registers they are finally set to required values.
Such rewriting should be only done for the unrecognized memory block by the BIOS. (The memory blocks such as the built-in 4MB and the expanded 16MB will be already recognized.)
The program over16s.com in your autoexec.bat will rewrite registers and restart PC110 automatically. It can be also worked by manual command. (This program can be used as a free software, as long as it is be used neither commercially nor militarily.)
The usage is as follows in this case.
over16s[ ///4]
over16s with no argument shows the contents of memory registers like B/0/5/0.
over16s ///4 will set the value of 4th bank to 8MB.
Here, 5 means 16MB, 4 means 8MB, and 3 means 4MB.
you may use d, c and b instead of 5, 4 and 3.
Results of setting.
This 32MB board can be used as the 16MB without assistant of the program. Using the setting program, it can be used as up 28MB (which cannot be the full size of 32MB by the limitation of the BIOS).
The left figure is two kinds of machine status indicated with the WinTip made by Mr. Ando.
The figure shows two status. The upper one of 4MB+16MB is unassisted case, and the lower one of 4MB+24MB is assisted case by the setting program.
(Comment : 4/ and 7/ have no means in this article.)
Go to other articles.
Preface Page, 1st:8MB(FP), 2nd:16MB(EDO), 3rd:16MB(FP), 4th:32MB(EDO), 6th:improved 16MB(EDO)
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The left figures are the wiring diagram and additional circuits.
Before soldering pins , *UCAS, *LCAS, *OE, *WE and *RAS pins of 5113165x chips should be slightly lifted up for soldering more easily and for avoiding to touch on the board surface.
This 32MB board can be used as the 16MB without assistant of the program. Using the setting program, it can be used as up 28MB (which cannot be the full size of 32MB by the limitation of the BIOS).