I built the "7Mhz Kit circuit" designed by Digital KC inside HB-F700S with the hope to get Turbo speed on Megaflashrom SCC+ SD, but i didn´t get Turbo speed with the cartidge, the cartidge neither worked using Msx Super Turbo on the HB-F700S or HB-F9S, i´m trying to find solutions to achieve this goal, because the Megaflashrom SCC+ SD work Ok in another machines modded with Turbo speed, like Dynadata dpc-200, Philips 8235 (modded with Z0858110PSC + 14.31818 MHz + Z84C0010PEC) builded by usuario_msx2 and other original machines like Panasonic WX at 5.58MHz. Maybe i could have a problem in my install, but i dont think so because the "7Mhz kit" and "Msx Super Turbo" works ok with all another hardware on that machines, anyways, maybe the Megaflashrom SCC+ SD cant work at Turbo speed in SONY machines? ,i dont think so, voltage problems?, should be a way but i dont know how find a solution...
I followed next steps to install "7Mhz Kit" on HB-F700S:
THE 7MHZ KIT:
Based in HansO info http://msx.hansotten.com/uploads/msxdocs/turbo7mhz.pdf i draw the piggy-bag pcb:
Components used:
-2 39PF smd capacitors
-1 14.31818 Mhz Cristal
-1 Z0858110PSC Zilog clock divider
-1 Z80 Z84C0010PEC (10Mhz Z80-H)
-1 Resistor 68K SMD
-1 100nF SMD capacitor
-1 560pF SMD capacitor
-6 1N4148 SMD diodes
-----------------------------------------------
-8 2200 ohm resistors (for HB-F700S)
-1 74ALS157 (for HB-F700S)
-----------------------------------------------
Pcb 7Mhz Kit piggy-bag conected to Z80 (NOTE: in this picture you´ll see a Z0858106PSC instead Z0858110PSC, i built this pcb with 6mhz clock divider + Z80 8Mhz for test purposes)
ASSEMBLY IN HB-F700S
- Cut jumper FB301 (near connection connector CN303) located on the upper pcb (clock output of the VDP, is no longer used, anyways i install a jumper opened instead cut only that point, this will use after to FIX PSG sound distorsion when Turbo is ON, explained a few lines below)
- Remove original IC14 (Z-80A or LH0080A) and install a New 40 Pin socket. At this point after remove Z80 i placed a mini protopcb in between to allow more easy get signals from Z80 to conect to external memory slot and F4 register. Also i extended-cut the CLK signal that now goes to a jumper (wires green and blue) and i get +5V (red wire) and GND(black wire) like I show in the pictures.
I decided extend that way signals because the pcb placed below socket will hide that conections forever.
- Remove original resistor array RB1, located under disk drive, and build a new resistor array using 2200 ohm resistors,(9 pins, eight resistors and one common). This resistance instruction is necessary to increase the rise time of the keyboard signals (separate keyboard) otherwise the keyboard will not work properly with Turbo.
- Place the Z80 Z84C0010PEC with the 7 MHz print mounted on top (piggy-bag conect to Z80) in new socket 40 PIN.
- Attach a wire between IC16 pin 10 and a free diode (automatically switch back to disk drive).
- Connect the selector switch between free and diode mass.
- Replace IC22 (74LS157) by a faster version (F-S-AS-ALS) to avoid switching problems with internal 512K or 1024K memory expansions (only for DRAM expansions?). I replaced for 74ALS157.
-I Use eproms 90ns (with a version msx2+ with basic 3.0 only, without logo, kanji, no faster diskrom version. I´m looking for a good 2+ implementation for HB-F700S, in picture i have F4 register installed directly to Z80, disabled 5V and GND jumpers, i dont have 2+ eproms prepared for use the F4 register yet)
At this point hardware works ok with Turbo ON, but PSG internal sound is distorted, to avoid this problem:
- I put FB301 jumper ON (to send CLK VDP 3.58Mhz to motherboard again)
- I put the CLK Z80 jumper OFF (to cut CLK Z80 signal and avoid mixing with CLK from VDP)
- Cut CLK track signal that goes to pin 42 (see image, this avoid CLK from VDP goes to SLOT1 and SLOT2)
- Make a conection between PIN6 Z80 CLK to slot PIN42 (see image, this conect CLK from Z80 directly to SLOT1 and SLOT2)
In the image above you can see how a blue conection goes from 3.58Mhz VDP (near CN11) to nowhere, this conection goes to the blue ones that appear in the image below, this modification with jumpers will allow set 3.58Mhz or Turbo CLK combinations for SLOT2:
(Tell that i tested Slot2 at 3.58Mhz when Turbo is ON and Megaflashrom SCC+ SD no works, neither MMC SD Sinfox, hang problems appear with SD hardware, other hardware like Cartidge Games worked ok)
512K SRAM
I have 512K SRAM cartidge conected directly to Z80 signals at SLT3-3, this cartidge is LPE-512KBSRAM-V3.
The questions are...why Megaflashrom SCC+ SD dont work at Turbo speed in HB-F700S when in other machines seems work well? What kind of differences had that modded machines compared to HB-F700S or HB-F9S? Could be any way to Fix it for work in Sony machines? Please, if anyone have machines working with Turbo and Megaflashrom SCC+ SD will be great to know models and how are installed, some pictures maybe could help...
