[NTLUG:Discuss] Re: HDTV card for Linux

[Bryan J. Smith]

On Tue, 2004-09-07 at 18:22, Lance Simmons wrote:
> July is what I had in mind.  I've never even actually _seen_ an HDTV
> picture so far as I know, but if I want to be able to record and save
> television shows in the future (after traditional TV is phased out), it
> looks like I need to get up to speed on HDTV sometime before July.
> Equipment sold after July will have a lot of restrictions on how you can
> use the signal.
> HDTV is on my to-do list, and I need to make sure July doesn't slip past
> before I do something about it.

FYI, NTSC MPEG-2 storage is typically 1GB/hour, HDTV is 10GB/hour.  So
to get even a decent amount of storage for HDTV, you want 300GB+.

So I'd definitely recommend a regular PC for HDTV PVR.

- Old PVR solutions and the ATA-4 limitations

The problem being the common IBM PowerPC 405 and various MIPS consortium
4000/5000-series variants have chipsets and reference designs that only
support ATA-4.  Although they have have upped the uC/EuP
(microcontroller/embedded microprocessor) clock and put in a more
powerful tuner/encoder, the platform remains the same in these black box
HDTV PVRs from what I've seen.  So they will not support more than
128GiB (133GB) of storage in an ATA device.

At 120GB, that's barely 12 hours.  24 hours for two disks on a single
ATA channel.  Not idea when you're pushing that much data around --
possibly for 2 tuners as well.

- Watch the I/O contention on a single, legacy, shared 0.125GB PCI bus

Also consider the I/O contention of a chipset that puts ATA and PCI on
the same, shared, 0.125GBps (32-bit at 33MHz) PCI bus.  Even with the
tunner/codec only sending 3-5MBps to the I/O, when you are pushing
multiple streams out to the I/O, there could be some contention between
I/O-memory-storage and frame drop.

PCI-Express will address this nicely, as even forthcoming, legacy AGP
mainboard will have (2) 0.25GBps PCI-Express x1 slots on the southbridge
-- which as a full 0.5-1GBps connection to the northbridge (either using
PCI-X, like the Intel ICH or older VLink, or 8+8-bit at 500MHz
HyperTransport like on all other chipsets, even for Intel CPUs,
including ViA's newer offering).  These (2) PCI-Express x1 slot
chipsets, both on the southbridge, from SiS and ViA should be out on
mainboard within the next 4-6 weeks.

As far as right now, consider a mainboard with at least a bridged PCI
solution into a 0.5GBps (64-bit at 66MHz) PCI/PCI-X master.  A ServerWorks
chipset mainboard is ideal for P3/P4 (the i7500-series is an Intel
rebranded), and don't knock the aging AMD AthlonMP using the 760MPX
(762+768 north+south).  Otherwise, and possibly overkill, a
HyperTransport system with something like the AMD8131 dual-PCI-X tunnel
-- but I haven't seen a single Socket-940 with it.  I'd wait for
PCI-Express and put either the tuner (not likely to see a card soon) or
ATA (more likely to see PCI-E x1 cards for ATA) on it.

-- Bryan

P.S.  In case you did not know, PCI-Express is _serial_ I/O and not
backward compatible with PCI.


-- 
Bryan J. Smith                                  b.j.smith at ieee.org 
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